is-qzss_14_e
TRANSCRIPT
IS-QZSS Ver. 1.4
Quasi-Zenith Satellite System
Navigation Service
Interface Specification for QZSS
(IS-QZSS)
V1.4
Japan Aerospace Exploration Agency
February 28, 2012
IS-QZSS Ver. 1.4
Preface
JAXA is pleased to announce the publication of IS-QZSS Version 1.4 on the QZSS website
(http://qzss.jaxa.jp/is-qzss/index_e.html) on 28 February 2012. This is a revision notice on the IS-QZSS
Version 1.3 previously released on June 2011. Main items to be updated are following;
Adding updated information for operating QZS-1 after the launching JAXA will gather comments on the
document from user communities as it was done for previous publication of IS-QZSS. JAXA always
welcomes comments and questions from users as part of our commitment to continually improve both this
IS-QZSS document and the QZSS. We also welcome communication with receiver manufacturers
concerning the design and manufacturing of receivers.
Disclaimer
(1) IS-QZSS and L-band Positioning Signal transmitted from QZS-1 (hereinafter referred to as “Signals” collectively) is provided without any
warranty including but not limited to accuracy, usefulness, Positioning Signal continuity and fitness for a particular purpose of use of the
Signals.
(2) No liability is assumed for any direct or indirect damages resulting from the use of the Signals, or from any product or service developed
based on the Signals.
IS-QZSS Ver. 1.4
REVISION RECORD
LTR DESCRIPTION DATE APPROVED
1.0 Initial release 17 June 2008
1.1 Adding new message type “No. 20” to LEX signal for the
experiment to be conducted by Geographical Survey Institute.
Adding notes on items to be modified according to the progress of
GPS L1C design.
31July 2009
1.2 Adding notes on QZSS L1C message description to be modified
according to the progress of GPS L1C message design.
Adding the information for L1-SAIF+ message
Adding the information for QZSS Website and Operational
information and Data
Adding notes on items to be modified according to the progress of
developing IMES(Indoor Messaging System)
Typo or editorial correction
25 Feb. 2011
1.3 Adding notes on QZSS L1C message description to be modified
according to the progress of GPS L1C message design.
Adding the information for SPAC-LEX signal
Adding updating information for QZS-1 operating after the
launching
Typo or editorial correction
22 June 2011
1.4 Adding updating information for QZS-1 operating after the
launching
Typo or editorial correction
28 Feb. 2012
IS-QZSS Ver. 1.4
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Table of Contents
1 SCOPE ..................................................................................................................................................... 1
2 APPLICABLE DOCUMENTS .............................................................................................................. 3
3 OVERVIEW OF QZSS .......................................................................................................................... 4
3.1 OVERVIEW OF QZSS ................................................................................................................. 5
3.1.1 System Overview .............................................................................................................. 5
3.1.2 Operation ........................................................................................................................ 12
3.1.3 Signals transmitted by QZS = QZS Signals .................................................................... 18
3.1.4 Time System and Coordinate System ............................................................................. 24
3.2 INTERFACE WITH OTHER SYSTEMS .......................................................................................... 25
3.2.1 QZSS Time System Relative to Other GNSS .................................................................. 25
3.2.2 QZSS Coordinate System Relative to Other GNSS ........................................................ 25
4 QZSS COVERAGE, AVAILABILITY AND PERFORMANCE .................................................... 27
4.1 QZSS SERVICE AREA .............................................................................................................. 27
4.1.1 Single QZS Coverage Area .............................................................................................. 27
4.1.2 QZSS Coverage Area ....................................................................................................... 28
4.1.3 Elevation Angle Variation for QZSS Constellation ......................................................... 29
4.1.4 QZSS constellation availability....................................................................................... 30
4.1.5 Target Regions for Ionospheric Parameters Transmitted by QZS .................................. 30
4.1.6 Availability Improvement when QZSS and Galileo are Combined with GPS ................ 31
4.2 SERVICE AVAILABILITY ............................................................................................................ 37
4.2.1 The fixed initial right ascension of ascending node depending on the launch time ....... 37
4.3 SYSTEM PERFORMANCE .......................................................................................................... 39
4.3.1 Availability ...................................................................................................................... 39
4.3.2 Alert flag, URA and Health Data .................................................................................... 39
4.3.3 Accuracy .......................................................................................................................... 40
5 QZSS SIGNAL PROPERTIES .......................................................................................................... 42
5.1 QZS POWER LEVELS, BANDWIDTHS AND CENTER FREQUENCIES ............................................. 42
5.1.1 Overview of signal properties ......................................................................................... 43
5.1.2 Navigational messages ................................................................................................... 50
5.2 L1C/A SIGNAL ......................................................................................................................... 54
5.2.1 RF characteristics ........................................................................................................... 54
5.2.2 Messages ......................................................................................................................... 54
5.3 L1C SIGNAL............................................................................................................................ 65
5.3.1 RF Characteristics .......................................................................................................... 65
5.3.2 Messages ......................................................................................................................... 66
5.4 L1-SAIF SIGNAL ..................................................................................................................... 83
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5.4.1 RF characteristics ........................................................................................................... 83
5.4.2 Error Correction Code ..................................................................................................... 83
5.4.3 Message ........................................................................................................................... 83
5.5 L2C SIGNAL .......................................................................................................................... 107
5.5.1 RF characteristics ......................................................................................................... 107
5.5.2 Message ......................................................................................................................... 107
5.6 L5 SIGNAL............................................................................................................................. 121
5.6.1 RF characteristics ......................................................................................................... 121
5.6.2 Message ......................................................................................................................... 121
5.7 LEX SIGNAL ......................................................................................................................... 136
5.7.1 RF Signal Characteristics ............................................................................................. 136
5.7.2 LEX Messages ............................................................................................................... 139
6 USER ALGORITHMS ....................................................................................................................... 164
6.1 CONSTANTS .......................................................................................................................... 164
6.1.1 Speed of Light ............................................................................................................... 164
6.1.2 Angular Velocity of the Earth's Rotation ...................................................................... 164
6.1.3 Earth's Gravitational Constant .................................................................................... 164
6.1.4 Circular Constant ......................................................................................................... 164
6.1.5 Semi-Circle .................................................................................................................... 164
6.2 USER ALGORITHMS RELATING TO TIME SYSTEMS AND COORDINATE SYSTEMS .......................... 164
6.2.1 User algorithms relating to time systems..................................................................... 164
6.2.2 User Algorithms relating to Coordinate Systems ......................................................... 165
6.3 COMMON GNSS ALGORITHMS ............................................................................................... 166
6.3.1 Time Relationships ....................................................................................................... 166
6.3.2 User Algorithm for SV Clock Offset .............................................................................. 167
6.3.3 Ionospheric Delay Correction for Dual Frequency Users ............................................. 168
6.3.4 Correction of Inter-Signal Group Delay Error by Users of Only One Signal ................ 171
6.3.5 Calculation of Satellite Orbit using Ephemeris Data ................................................... 172
6.3.6 Calculation of Satellite Orbit and SV Clock Offset using Almanac Data ..................... 172
6.3.7 Calculation of Coordinated Universal Time (UTC) using the global standard time
parameter .............................................................................................................................. 174
6.3.8 Correction of Ionospheric Delay Using Ionospheric Parameters .................................. 174
6.3.9 Correction Using NMCT (L1C/A Signal) and DC Data (L1C, L2C and L5 Signals) ..... 174
6.3.10 User Algorithms Relating to Interoperability with Other Satellite Navigation Systems
175
6.4 L1 SAIF ALGORITHM ............................................................................................................ 176
6.4.1 Validity period (Time-out period) .................................................................................. 176
6.4.2 Error Correction Algorithm........................................................................................... 176
6.4.3 Algorithm for Integrity information .............................................................................. 183
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6.4.4 Calculation of QZSS satellite Position .......................................................................... 185
6.5 LEX ALGORITHM .................................................................................................................. 186
6.5.1 Reed Solomon Coding/Decoding Algorithm for LEX Navigation Message.................... 186
6.6 OTHER INFORMATION ........................................................................................................... 189
6.6.1 Instrumental Bias in Receivers .................................................................................... 189
7 PROVISION OF QZSS OPERATIONAL INFORMATION AND DATA VIA THE INTERNET
190
7.1 QZSS WEBSITE FOR OPERATIONAL INFORMATION AND DATA ................................................. 190
7.2 RELEASE OF QZSS INFORMATION AND DATA ......................................................................... 190
7.2.1 NAQU (NOTICE ADVISORY TO QZSS USERS) ....................................................... 190
7.2.2 Experimental Schedule ................................................................................................. 191
7.2.3 Evaluation result for System Performances ................................................................. 191
7.2.4 User Operation Support Tool ........................................................................................ 191
7.2.5 Provision of Precise Orbit & Clock for QZSS and GPS ................................................. 192
7.2.6 Detailed Information for Precise Orbit & Clock Estimation for research purposes ..... 192
8 DIFFERENCES WITH GPS ............................................................................................................. 193
8.1 DIFFERENCES IN NAVIGATION MESSAGES .............................................................................. 193
8.1.1 Differences with GPS in terms of L1C/A signal ............................................................ 193
8.1.2 Differences with GPS in terms of CNAV message on L2C and L5 signals ................... 194
8.1.3 Differences with GPS in terms of CNAV2 message on L1C signals ............................. 195
8.2 DIFFERENCE OF RF CHARACTERISTICS ................................................................................. 197
8.2.1 Difference of Modulated Diffusion Method of Signal .................................................... 197
8.2.2 Difference of Signal Phase Relation of LIC Signal ....................................................... 197
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List of Figures Figure 3.1.1-1 System overview........................................................................................... 5
Figure 3.1.1-2 QZSS Orbit and Ground Track Diagram for the Three-Satellite Constellation....... 6
Figure 3.1.1-3 Constellation Orbit Track Diagram (EPOCH=2009/Dec/26/12:00UTC) for the
Three-Satellite Constellation ........................................................................................ 6
Figure 3.1.1-4 QZS Orbit Ground Tracks ............................................................................. 8
Figure 3.1.1-5 QZS ........................................................................................................... 9
Figure 3.1.1-6 QZS Block Diagram ...................................................................................... 9
Figure 3.1.1-7 Mapping of Ground Stations ..........................................................................10
Figure 3.1.1-8 MCS ..........................................................................................................11
Figure 3.1.1-9 TTC Antenna .............................................................................................11
Figure 3.1.2-1 System data flow .........................................................................................12
Figure 3.1.2-2 An example of the update timing of the navigation message ...............................13
Figure 3.1.2-3 An example of uplink timing of the navigation message .....................................14
Figure 3.1.2-4 Relationship between "Alert" flag and URA/NSC switching ...............................16
Figure 3.1.2-5 Range of Orbital Maintenance .......................................................................17
Figure 3.1.3-1 Power Spectral Density of QZS Signals ...........................................................18
Figure 3.1.3-2 Relative velocity of signals (Change rate of distance) between each city and QZS-1
(See Table 3.1.1-1 for calculation condition. Observation EPOCH = 2009/Dec/26/12:00UTC.
Horizontal axis means elapsed time from EPOCH.) .........................................................20
Figure 3.1.3-3 Elevation and Azimuthal angles for each city (See Table 3.1.1-1 for calculation
condition. Observation EPOCH = 2009/Dec/26/12:00 UTC) ..........................................22
Figure 3.1.3-4 Changes of received signal power level for each city (See Table 3.1.1-1 for
calculation condition. Observation EPOCH = 2009/Dec/26/ 12:00 UTC. Horizontal axis
means elapsed time from EPOCH.) ...............................................................................23
Figure 3.2.1-1 Diagram of Time System Relationships between QZSS, GPS and Galileo ..............25
Figure 3.2.2-1 Convergence of Geodetic Coordinate Systems .................................................26
Figure 4.1.1-1 Percentage of Time during which a Single QZS can be seen at an Elevation Angle of
10° or more .............................................................................................................27
Figure 4.1.1-2 Percentage of Time during which a Single QZS can be seen at an Elevation Angle of
60° or more .............................................................................................................27
Figure 4.1.2-1 Percentage of Time during which at least One QZS in the 3-satellite QZSS
constellation can be seen at an Elevation Angle of 10° or more ......................................28
Figure 4.1.2-2 Percentage of Time during which at least One QZS in the 3-satellite QZSS
constellation can be seen at an Elevation Angle of 60° or more ......................................28
Figure 4.1.3-1 Variation of QZSS Constellation (for 3 satellites) Elevation Angles for eight cities
(See Table 3.1.1-1 for calculation condition of QZS-1. For QZS-2 and 3, we assumed the right
ascension of ascending node is +/- 120 deg from that value of QZS-1. Observation EPOCH =
2009/Dec/26/12:00UTC Horizontal axis means elapsed time from EPOCH.) .....................29
Figure 4.1.4-1 Average Number of QZS Satellites that can be seen at an Elevation Angle of 10° or
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more with the 3-satellite QZSS Constellation .................................................................30
Figure 4.1.5-1 Target Regions for Ionospheric Parameters Transmitted by QZS ........................30
Figure 4.1.6-1(1/2) Percentage of Time when PDOP < 6 for an Elevation Angle Mask of 20° ....32
Figure 4.1.6-2 (1/3) Average Number of Visible Satellites for an Elevation Angle Mask of 10° ..34
Figure 4.2.1-1 Initial Single-satellite QZSS Visibility Time for eight Reference Locations. (See Table
3.1.1-1 for calculation condition. Dark shaded areas represent elevation angles of 60[deg] or
more; light blue areas represent elevation angles of 10[deg] to 60[deg] and white is less than
10[deg]; vertical scale is hours on UTC and JST.) ..........................................................38
Figure 4.3.2-1 “Alert” flag, URA, Health Data and Integrity Data Maximum Notification Time ...40
Figure 5.1.1-1 Phase Relations of LI Signal for QZS-1 and GPS ..............................................44
Figure 5.1.1-2 Phase Noise of all QZS signals.......................................................................45
Figure 5.1.1-3 Definition of code jitter σjitter........................................................................46
Figure 5.1.1-4 Definition of delay time, Δ, for PRN code rising/falling edge .............................47
Figure 5.1.2-1 QZS URA and Health Data on L1C/A signal ...................................................50
Figure 5.3.1-1 L1C Signal Structure ...................................................................................65
Figure 5.3.2-1 Relationship between TOI, ITOW & time of week ............................................69
Figure 5.4.2-1 FEC Generation Method ..............................................................................83
Figure 5.4.3-1 Message Block Format .................................................................................84
Figure 5.6.1-1 L5 Signal Structure .................................................................................... 121
Figure 5.7.1-1 LEX Signal Structure ................................................................................. 136
Figure 5.7.1-2 Block diagram of LEX code generation ......................................................... 137
Figure 5.7.1-3 Timing Relationship between the LEX Short Code and Long Code ................... 138
Figure 5.7.2-1 LEX Message Structure ............................................................................. 139
Figure 5.7.2-2 Reed-Solomon Encoding ............................................................................. 141
Figure 5.7.2-3 Data Part, Message Type 10 – Signal Health, Ephemeris & SV Clock ............... 142
Figure 5.7.2-4 Data Part, Message Type 11 – Signal Health, Ephemeris & SV Clock and Ionospheric
Correction .............................................................................................................. 143
Figure 5.7.2-5 Signal Health Packet Structure .................................................................... 145
Figure 5.7.2-6 Ephemeris & SV Clock Packet Content ........................................................ 148
Figure 5.7.2-7 Ionospheric Correction Packet Content ........................................................ 155
Figure 6.4.2-1 Definition of interpolation with four surrounding IGPs ..................................... 180
Figure 6.4.2-2 Definition of interpolation with three surrounding IGPs ................................... 181
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List of Tables Table 3.1.1-1 Calculation condition for QZS-1 nominal orbit ................................................... 8
Table 3.1.1-2 Location of Ground Station ............................................................................10
Table 3.1.3-1 General Specifications for QZS Signals.............................................................19
Table 3.1.3-2 Doppler coefficients for signals .......................................................................21
Table 4.3.3-1 Positioning Accuracy by means of Availability Enhancement Signals ....................41
Table 4.3.3-2 Positioning Accuracy by means of Performance Enhancement Signals ...................41
Table 5.1-1 QZS signal specifications ..................................................................................42
Table 5.1.1-1 Configuration of QZS signals ..........................................................................43
Table 5.1.1-2 Differences in Pseudo Random Noise (PRN) code phases among QZS signals .........48
Table 5.1.2-1 Details of Health (5-bit health) code for all QZSS signals ...................................51
Table 5.2.2-1 Content identification using Data ID and Space Vehicle ID .................................59
Table 5.2.2-2 Sequence of Satellite Health in the frame when Data-ID=11 ...............................61
Table 5.2.2-3 Sequence of NMCT in the frame when Data-ID=11 ...........................................64
Table 5.3.2-1 Definition of Ephemeris parameters and SV clock parameters for Navigational Message
DL1C .........................................................................................................................68
Table 5.3.2-2 Definition of page number and transmit periods for Navigational Message DL1C ......72
Table 5.3.2-3 Definition of UTC parameters and Ionospheric parameters for Navigational Message
DL1C .........................................................................................................................73
Table 5.3.2-4 Definition of GPS GNSS Time Offset (GGTO) and EOP parameters for Navigational
Message DL1C ............................................................................................................75
Table 5.3.2-5 Definition of Reduced Almanac parameters for Navigational Message DL1C ............76
Table 5.3.2-6 Definition of Midi Almanac parameters for Navigational Message DL1C ..................79
Table 5.3.2-7 Definition of DC data for Navigational Message DL1C .........................................81
Table 5.4.3-1 SAIF Message Types .....................................................................................85
Table 5.4.3-2 Message Type 1: PRN Mask Data ...................................................................87
Table 5.4.3-3 PRN Slot Assignments to GNSS Satellites ........................................................88
Table 5.4.3-4 Message Types 2 - 5: Fast Correction ............................................................89
Table 5.4.3-5 UDRE value .................................................................................................89
Table 5.4.3-6 Message Type 6: Integrity Data ......................................................................90
Table 5.4.3-7 Message Type 7: Fast Correction Degradation Factor .......................................90
Table 5.4.3-8 Message Type 10: Degradation Parameter........................................................91
Table 5.4.3-9 Message Type 18 Format: IGP Mask ...............................................................92
Table 5.4.3-10 Specification of IGP locations .......................................................................93
Table 5.4.3-11 Message Type 24 (Fast & Long-term Corrections) ..........................................98
Table 5.4.3-12 Message Type 25: Long-Term Correction ......................................................99
Table 5.4.3-13 Partial message format of Message Type 25 ....................................................99
Table 5.4.3-14 Message Type 26: Ionospheric Delay Correction ........................................... 100
Table 5.4.3-15 GIVEI Value ............................................................................................. 100
Table 5.4.3-16 Message Type 28: Clock - Orbit Covariance ................................................ 101
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Table 5.4.3-17 Message Type 63 (Null Message) ................................................................ 101
Table 5.4.3-18 Message Type 52:TGP Mask...................................................................... 102
Table 5.4.3-19 Specification of TGP locations .................................................................... 103
Table 5.4.3-20 Message type 53:Zenith Tropospheric Delay Correction ................................ 105
Table 5.4.3-21 Message Type 56: Inter Signal Bias Correction Data ...................................... 105
Table 5.4.3-22 QZS Ephemeris Data ................................................................................. 106
Table 5.5.2-1 Definitions of message types for Navigational Message DL2C .............................. 108
Table 5.5.2-2 Maximum Transmit periods for Navigational Message DL2C ................................ 108
Table 5.5.2-3 Definition of Ephemeris parameters for Navigational Message DL2C .................... 110
Table 5.5.2-4 Definition of SV clock parameters for Navigational Message DL2C ...................... 112
Table 5.5.2-5 Definition of ionospheric parameters for Navigational Message DL2C ................... 113
Table 5.5.2-6 Group Delay Correction Parameters (TGD, ISC) for Navigational Message DL2C .... 114
Table 5.5.2-7 Definition of Midi Almanac parameters for Navigational Message DL2C ................ 115
Table 5.5.2-8 Definition of Reduced Almanac parameters for Navigational Message DL2C .......... 115
Table 5.5.2-9 Definition of parameters for DC data for Navigational Message DL2C .................. 119
Table 5.5.2-10 Definition of GPS GNSS Time Offset (GGTO) parameters for Navigational Message
DL2C ....................................................................................................................... 120
Table 5.6.2-1 Definitions of message types for Navigational Message DL5 ............................... 122
Table 5.6.2-2 Maximum Transmit periods for Navigational Message DL5 ................................. 123
Table 5.6.2-3 Definition of Ephemeris parameters for Navigational Message D L5 ..................... 125
Table 5.6.2-4 Definition of SV clock parameters for Navigational Message D L5 ....................... 127
Table 5.6.2-5 Definition of ionospheric parameters for Navigational Message D L5 .................... 128
Table 5.6.2-6 Group Delay Correction Parameters (TGD, ISC) for Navigational Message D L5 ..... 129
Table 5.6.2-7 Definition of Midi Almanac parameters for Navigational Message DL5 ................. 130
Table 5.6.2-8 Definition of Reduced Almanac parameters for Navigational Message DL5 ............ 130
Table 5.6.2-9 Definition of parameters for DC data for Navigational Message DL5 .................... 134
Table 5.6.2-10 Definition of GPS GNSS Time Offset (GGTO) parameters for Navigational Message
DL5 ......................................................................................................................... 135
Table 5.7.1-1 LEX code phase assignment ......................................................................... 138
Table 5.7.2-1 Definition of message type ........................................................................... 140
Table 5.7.2-2 Definition of ephemeris parameters for Navigational Message DLEX navigation message
............................................................................................................................. 149
Table 5.7.2-3 Definition of SV clock and group delay parameters for Navigational Message DLEX
navigation messages ................................................................................................. 153
Table 5.7.2-4 Definition of ionospheric correction parameters for LEX navigation messages ..... 154
Table 5.7.2-5 Message type 10,11:broadcast interval, update interval and valid time .............. 157
Table 5.7.2-6 The Record Structure of Message Type 20 ..................................................... 158
Table 5.7.2-7 Parameter-type ID...................................................................................... 158
Table 5.7.2-8 Observation Information of the Reference Stations .......................................... 159
Table 5.7.2-9 GPS Smoothing Interval ............................................................................... 160
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Table 5.7.2-10 GPS L1 Lock time Indicator ....................................................................... 160
Table 5.7.2-11 Satellite Orbit and Clock Correction Information + Ionosphere Grid Interval
Information .............................................................................................................. 161
Table 5.7.2-12 Tropospheric Delay Correction Information .................................................. 162
Table 5.7.2-13 Ionospheric Delay Correction Information .................................................... 162
Table 6.4.1-1 Validity Periods for L1-SAIF Message Parameters .......................................... 176
Table 6.4.3-1 Relations of integrity and Constants “K” ....................................................... 183
Table 7.2-1 Provision of QZSS Information and Data ........................................................... 190
Table 7.2.3-1 Test Evaluation Public Release Data List ....................................................... 191
Table 8.1.1-1 Parameters with definitions unique to QZSS ................................................... 193
Table 8.1.2-1 Parameters with definitions unique to QZSS ................................................... 194
Table 8.1.3-1 Parameters with definitions unique to QZSS ................................................... 195
IS-QZSS Ver. 1.4
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1 Scope
This Interface Specification (IS-QZSS) presents an overview of the Quasi-Zenith Satellite System
(QZSS1) being developed by the Japan Aerospace Exploration Agency (JAXA) and defines the interface
between the Space Segment (SS) provided by the Quasi-Zenith Satellites (QZS2), and the User Segment
(US) of the QZSS. IS-QZSS was prepared to encourage the use of the positioning, navigation and timing
services of QZSS which are freely available for peaceful means to anyone who has visibility to one or
more QZS.
QZSS signals have been designed and developed so as to maximize the interoperability with the
NAVSTAR Global Positioning System (GPS) operated by the United States (U.S.) as well as to provide
compatibility of QZSS with GPS and other space-based systems that comprise the Global Navigation
Satellite System (GNSS). The QZSS signal design reflected in this document was established through
closely collaborated discussion with in the U.S.-Japan GPS QZSS Technical Working Group.
IS-QZSS provides general information regarding the QZSS system and services and also covers service
performance, QZSS signal characteristics and recommended user algorithms. QZSS is designed to work
in conjunction with, and enhance, the civil services of GPS. Therefore, this document makes reference to
the public domain GPS interface specification documents listed in Section 2 below. IS-QZSS describes
in detail all differences with respect to GPS that user equipment designers must be aware of to make full
use of the enhanced capabilities possible when QZSS signals are received in addition to GPS signals.
This specification is intended for all users of QZSS and includes information about utilizing the L1C/A,
L1C, L1-SAIF, L2C, L5 and LEX signals transmitted by Quasi-Zenith Satellites (QZS).
This IS-QZSS document has been updated several times since the publication of the first draft edition
due to the progress of the system design and development. In this IS-QZSS Version 1.0 release, the
signal types signal strengths, signal structures, and other elements from the previous release of IS-QZSS
have been updated. JAXA welcomes and encourages feedback from QZSS users. IS-QZSS will be
reviewed and revised in response to valuable user feedback in addition to the progress of the QZSS
design, the technology demonstration after the launch of the first QZS, the results of the utilization
demonstration, etc., from the viewpoints of manner of operation, handling of data, readability, and others.
Upon the release of the next revision of IS-QZSS, the comments of users will again be taken into
consideration.
1 QZSS is an abbreviation for Quasi Zenith Satellite System and refers to the system as a whole.
2 QZS is an abbreviation for Quasi Zenith Satellite and refers specifically to these satellites.
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Application demonstration will be mainly conducted by the private sector. Satellite Positioning Research
and Application Center (SPAC) will be a coordinator for user interface among related organizations.
Section 3 of IS-QZSS presents an overview of the Quasi-Zenith Satellite System. The availability,
geographical coverage and system performance provided by QZSS are introduced in Section 4. Sections
5 to 8 contain the details of the interface specification and signal description. Section 5 specifies the
QZSS signal properties including RF characteristics, message structure and data format. Section 6
contains user algorithms to be incorporated in receiver designs. Section 7 provides information regarding
obtaining QZSS operational data via the internet. Finally, the differences between QZSS and GPS
messages are summarized in Section 8 for the convenience of users.
The specification for L1-SAIF signal in Section 4.3.2 “Alert flag, URA and Health Data”, Section 4.3.3.5
“Positioning Accuracy by means of Performance Enhancement Signals”, Section 5.4 “L1-SAIF signal”
and Section 6.4 “L1 SAIF Algorithm” are development results by Electronic Navigation Research
Institute. And also, the information about “L1-SAIF+ message” in Section 5.4.3.1.2 and 5.4.3.5 reflects
the fruits of research and development by Satellite Positioning Research and Application Center. The
detailed specification defined the interface will be issued by Satellite Positioning Research and
Application Center separately.
The specification for the definition of message type for LEX signal in Section 5.7.2.2.2 is development
results by Geographical Survey Institute. And detailed specifications for messages type 156 - 255 in
Section 5.7.2.2.4 have been issued by Satellite Positioning Research and Application Center (in Section 2
"Applicable Document" (6)).
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2 Applicable Documents
(1) Navstar GPS Space Segment/Navigation User Interface, Interface Specification, IS-GPS-200.
Rev. E, June 2010.
(2) Navstar GPS Space Segment/User Segment L5 Interfaces, Interface Specification, IS-GPS-705.
Rev. A, June 2010.
(3) Navstar GPS Space Segment/User Segment L1C Interfaces, Interface Specification, IS-GPS-200.
Rev. E, June 2010.
(4) International Standards and Recommended Practices, Aeronautical Telecommunications, Annex
10 to the Convention on International Civil Aviation, vol. I, ICAO, Nov. 2002.
(5) Minimum Operational Performance Standards for Global Positioning System/Wide Area
Augmentation System Airborne Equipment, DO-229C, RTCA, Nov. 2001.
(6) SPAC- -100630-15, Quasi-Zenith Satellite System Navigation Service Application
Demonstration, Augment Message Specification for QZSS, Satellite Positioning Research and
Application Center, July 2011.
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3 Overview of QZSS
The Quasi-Zenith Satellite System (QZSS) is a regional space-based positioning system that uses a
constellation of satellites placed in multiple orbital planes. The satellites have the same orbital period as
a traditional equatorial geostationary orbit, however, they have a large orbital inclination and therefore
move with respect to the Earth. The QZS orbits are also elliptical and are sometimes known as
“highly-inclined elliptical orbits” or HEO. The system covers regions in East Asia and Oceania centering
on Japan and is designed to enable users in the coverage area to receive QZS signals from a high
elevation angle at all times.
QZSS enhances GPS services in the following two ways: 1) Availability enhancement (improving the
availability of GPS signals) and 2) Performance enhancement (increasing the accuracy and reliability of
GPS signals).
By broadcasting signals that are similar to and compatible with GPS, QZSS enhances standalone GPS
availability for any user that has visibility to, and can track, one or more QZS. This enhancement will be
the greatest for users in the region of Japan because the constellation design is optimized for that area.
However, users in many other Asia-Pacific areas will also benefit from the enhanced geometric
arrangement made possible by QZSS. This increases the area and times at which positioning is possible
in both urban and mountainous areas where a portion of the sky is often blocked from view.
To ensure interoperability and compatibility with modernized GPS civil signals, the GPS availability
enhancement signals transmitted from QZSS satellites use modernized GPS civil signals as a base,
transmitting the L1C/A, L1C, L2C and L5 signals. This minimizes changes to specifications and receiver
designs. Additionally, L1C and L5 of above signals transmitted by QZSS have interoperability with not
only GPS but also Galileo and other GNSS in future multi-GNSS era.
QZSS further improves standalone GPS accuracy by means of ranging correction data provided through
the transmission of submeter-class performance enhancement signals L1-SAIF and LEX from QZS. It
also improves reliability by means of failure monitoring and system health data notifications. QZSS also
provides other support data to users to improve GPS satellite acquisition.
The QZSS project will be implemented incrementally in accord with the official policy of the
Government of Japan released on March 31, 2006 as follows.
Phase One: Technical validation and application demonstration will be conducted with the first QZSS
satellite.
Phase Two: Following the successful completion of Phase One, the 2nd and 3rd QZSS satellites will be
launched. Full system operation will be demonstrated.
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3.1 Overview of QZSS
3.1.1 System Overview
QZSS consists of (a) the QZSS Space Segment (SS) comprised of a constellation of Quasi-Zenith Satellites (QZS) orbiting the Earth, and (b) the QZSS Ground Segment (GS) comprised of Monitor Stations (MS), a Master Control Station (MCS), Tracking Control Stations (TCS) and Time Management Station (TMS). A system diagram is provided in Figure 3.1.1-1. QZS signals are transmitted from the QZS and monitored by the MS. The MCS collects the MS monitoring results and estimates and predicts the QZS time and orbit. The MCS also gathers other data as well and generates navigation messages, and uplinks to the QZS via the Tracking Control Station. The Tracking Control Stations constantly monitor the status of the QZS and function in cooperation with the MCS to provide appropriate services as needed. In addition, approximately once per year, the TCS exercise orbital control to ensure that the QZS is maintained in the correct orbital position.
Figure 3.1.1-1 System overview
3.1.1.1 Overview of QZSS Space Segment
The QZSS Space Segment (SS) consists of initially one satellite, and ultimately three (or more) satellites having the characteristics described below. 3.1.1.1.1 QZSS Constellations
The baseline QZSS constellation is comprised of three satellites as illustrated below. All QZS are in orbits that have the same “figure-8” ground track (passing over Southeast Asia, Australia, etc.) as shown in Figure 3.1.1-2 and Figure 3.1.1-4. The orbit tracks of the 3 satellites are shown in Figure 3.1.1-3.
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Figure 3.1.1-2 QZSS Orbit and Ground Track Diagram for the Three-Satellite Constellation
Equator 0
40
80
120
160
320
280
240
200
Argumen
t of L
atitud
e [de
g]
Orbital
Plane C
(RAAN=9
0deg
)
Orbital
Plane B
(RAAN=3
30de
g)RAAN
Orbital
Plane A
(RAAN=2
10de
g)
QZS1
QZS3
QZS2
Note1: Tentative for QZS2 and QZS3
43 degreeEquator 0
40
80
120
160
320
280
240
200
Argumen
t of L
atitud
e [de
g]
Orbital
Plane C
(RAAN=9
0deg
)
Orbital
Plane B
(RAAN=3
30de
g)RAAN
Orbital
Plane A
(RAAN=2
10de
g)
QZS1
QZS3
QZS2
Note1: Tentative for QZS2 and QZS3
43 degree
Figure 3.1.1-3 Constellation Orbit Track Diagram (EPOCH=2009/Dec/26/12:00UTC) for the
Three-Satellite Constellation
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3.1.1.1.2 Orbits
The parameters defining the QZS nominal orbits are provided below. The satellites have the same orbital period as a traditional equatorial geostationary satellite, however, they have a large orbital inclination so they do not remain in the equatorial plane and therefore move with respect to the Earth. The QZS orbits are also elliptical and are sometimes known as “highly-inclined elliptical orbits” or HEO. The QZS will orbit somewhat further from the Earth in the Northern Hemisphere than in the Southern Hemisphere. These orbits result in a longer period of high elevation angle service for the region of Japan. Ultimately a single satellite will be deployed in each of the three orbital planes, thereby providing continuous coverage at high elevation angles for the primary service areas (including all Japanese territory). 3.1.1.1.2.1 Semi-Major Axis (a)
a = 42164 km (average)
3.1.1.1.2.2 Eccentricity (e)
e = 0.075 +/- 0.015
3.1.1.1.2.3 Orbital inclination (i)
i = 43°+/-4°
3.1.1.1.2.4 Right Ascension of Ascending Node (Ω)
With the argument of perigee, the right ascension of ascending node for each satellite is designed to maintain the central longitude of the ground track (see Section 3.1.1.1.2.6). The initial right ascension of ascending node of Quasi-Zenith Satellite-1 (QZS-1) Ω0 is set at about 195[deg]. For the 3-satellites QZSS constellation, the initial right ascension of ascending node of QZS-2 & 3 is going to be set at that of QZS-1 +/- 120[deg].
3.1.1.1.2.5 Argument of Perigee (ω)
ω = 270+/-2°
3.1.1.1.2.6 Central Longitude of Ground Trace
The central longitude of ground trace is the center of the 8-figure ground trace, and is the center of two longitudes of ascending and descending. The longitude value is maintained 135° East +/- 5° .
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3.1.1.1.3 QZS orbit Ground Tracks
Figure 3.1.1-4 shows the QZS orbit ground tracks (See Table 3.1.1-1 for calculation condition).
Figure 3.1.1-4 QZS Orbit Ground Tracks
Table 3.1.1-1 Calculation condition for QZS-1 nominal orbit
No. Item Setting 1 Epoch 26 Dec. 2009, 12:00:00 (UTC) 2 Semi-Major Axis [km] 42164.16945 3 Eccentricity 0.075 4 Orbital inclination [deg] 43.0 5 Right Ascension of Ascending Node [deg] 195.0 6 Argument of Perigee [deg] 270.0 7 Mean Anomaly [deg] 305.0
3.1.1.1.4 QZS
Figure 3.1.1-5 shows an illustration of a QZS. It has two deployable solar cell array panels, an L-band transmission antenna (L-ANT), an L1-SAIF transmission antenna (LS-ANT), TTC antennas, and a Ku-band Time Transfer Antenna (Ku-ANT). The QZS utilizes fixed (non-steerable) antennas mounted on one side of the spacecraft. The QZS attitude is controlled to ensure that these antennas always point toward the center of the Earth. Yaw steering controls the orientation of the solar cell arrays to optimize reception of sunlight. The L-ANT is made up of a helical antenna array. The gain curve formed by this array is designed to provide signals with constant power levels at any location on the ground by compensating for the Earth’s surface shape.
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Figure 3.1.1-5 QZS
The QZS includes the equipment shown in Figure 3.1.1-6 that is used to generate and transmit QZS signals. QZS signals comprise a carrier wave that uses a rubidium atomic clock as a frequency reference and that is modulated by PRN codes and navigation messages generated by the MCS. These signals are transmitted toward the Earth from the L-ANT and LS-ANT.
Time
Comparison
Unit
Time TransferSystem
RF portion
RbAtomic Clock
TimeKeeping
UnitSynthesizer
Navigation
Operation
Computer
Modulator Amplifier
Laser
Reflector
RbAtomic Clock
Sine Wave
Signal of Two Way Satellite Time and Frequency Transfer
Navigation Signal
TimeKeeping
UnitSynthesizer
Navigation
Onboard
Computer
Modulator Amplifier MUX
TimeComparison
Unit
Time TransferSystem
RF portion Ku-Ant
L-Ant
Uploaded Data(including Remote Synchronization
Signal)
Baseband Signal (Navigation Message + PRN Code)
ControlPhase Error
QZSL1-SAIF-Ant
TT&C
TT&C
Subsystem
TLM
Navigation Message, CMD
Figure 3.1.1-6 QZS Block Diagram
3.1.1.2 Overview of Ground Segment
The QZSS Ground Segment consists of multiple Earth-based stations. These comprise Monitor Stations (MS) that are widely distributed and observe QZS and GPS signals on the ground; a Master Control Station (MCS) that collects the results of monitoring from all of the MS, estimates and predicts QZSS and GPS clock offsets and orbits, generates navigation messages, etc.; Tracking Control Stations that uplink navigation messages and monitor QZS status, and the Time Management Station (TMS) for time transfer.
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There are nine MS dispersed throughout the area from which QZS signals can be received (Refer
to Figure 3.1.1-7). The MCS (Refer to Figure 3.1.1-8) and TMS are located in Japan. The rough
locations of each Ground Stations are shown in Table 3.1.1-2.
-90
-60
-30
0
30
60
90
0 30 60 90 120 150 180 210 240 270 300 330 360
Lat
itude
Longitude
Hawaii
Guam
Canberra
Bangalore
Sarobetsu
Koganei
TsukubaOkinawa
Chichijima
Bangkok
Figure 3.1.1-7 Mapping of Ground Stations
Table 3.1.1-2 Location of Ground Station
No. Place Location (Longitude and Latitude)
1 Koganei East longitude 139.4882° North latitude 35.7078°
2 Sarobetsu East longitude 141.7489° North latitude 45.1636°
3 Okinawa East longitude 127.8444° North latitude 26.4986°
4 Chichi-Jima East longitude 142.2154° North latitude 27.0792°
5 Hawaii West longitude 159.6650° North latitude 22.1262°
6 Guam East longitude 144.7948° North latitude 13.4774°
7 Bangkok East longitude 100.6130° North latitude 14.0823°
8 Bangalore East longitude 77.5116° North latitude 13.0343°
9 Canberra East longitude 149.0104° South latitude 35.3160°
-90
-60
-30
0
30
60
90
0 30 60 90 120 150 180 210 240 270 300 330 360
Longitude
Lat
itude
系列1
系列2
Master Control Station
QZSS Monitor Station
Tracking Control Station
Hawaii
Guam
Canbera
India
Sarobetsu
Koganei
TsukubaOkinawa
Chichijima
Thailand
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Figure 3.1.1-8 MCS
Several Tracking Control Stations are strategically positioned at locations that enable continuous monitoring and control of the QZS. Two Tracking Control Stations are constructed in the Okinawa Tracking and Communication Station for the first development phase of Quasi-Zenith Satellite System. Figure 3.1.1-9 shows the type of TTC antenna with which each Tracking Control Station is equipped.
Figure 3.1.1-9 TTC Antenna
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3.1.2 Operation
3.1.2.1 Data
3.1.2.1.1 Data Flow
Figure 3.1.2-1 shows an overview of the QZSS data flow.
(1) QZS signals and signals from other GNSS are received by the Monitor Stations (MS).
(2) The results of monitoring by the MS are sent to the Master Control Station (MCS) where
QZSS and other GNSS orbits and times are estimated and propagated to predict future
satellite positions and system times.
(3) Based on the results of orbit and time estimates and predictions, navigation messages are
generated and sent to the Tracking Control Stations.
(4) At the Tracking Control Stations, the navigation messages are uploaded to the QZS
On-board Control Computer by way of the Telemetry Command Subsystem.
(5) On-board the QZS, a signal with the navigation messages superimposed are generated and
transmitted to the Earth via the L-band transmission antenna and the L1-SAIF transmission
antenna.
Figure 3.1.2-1 System data flow
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3.1.2.1.2 Navigation Message Update and Uplink
The navigation messages in the QZS signals, except the L1-SAIF and LEX signals, are updated
with the timing shown in Figure 3.1.2-2. For this purpose, QZSS uplinks the appropriate
navigation messages at the necessary intervals by way of the Tracking Control Stations.
Ephemeris data and Almanac data, excluding SV Clock parameters and Differential data, are
updated every 3600 seconds. SV Clock parameters are updated every 900 seconds. URA of the
signals are updated every 30 seconds for L1C/A, every 18 seconds for L1C, every 48 seconds
for L2C and every 24 seconds for L5. Other information are depends on navigation pattern table
(see Section 7.2.4.3). Orbit Parameters of Ephemeris data is valid for 7200 seconds, and SV
Clock Parameters are valid for 1800 seconds.
The navigation messages of the L1-SAIF and LEX signals are uploaded from MCS,
superimposed upon navigation signals on OZS and transmitted to the Earth continuously.
1week = 604800s
3600s
Time of Week
00:00:00
(Week Number = n)
900s
(1)Ephemeris, Almanac
other than (2)(3)
(2)SV Clock Parameter
(3)Differential Data
3600s 3600s
300s300s
300s300s
300s300s
TOW
00:00:00
(WN = n+1)
900s 900s 900s 900s 900s 900s 900s 900s 900s 900s 900s900s
Figure 3.1.2-2 An example of the update timing of the navigation message
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Further Navigation message timing details are provided in Figure 3.1.2-3.
L1C/A
Overall message
Ephemeris, Clock
Overall message
Ephemeris, Clock
at 15-min intervals
time
URA INDEX, NMCT, AODO
5min(300s)
at 15-min intervals
EDC, CDC
URA INDEX
Hour(Overall message update)
Hour(Overall message update)
Overall message
Ephemeris, Clock
at 15-min intervals
EDC, CDC
URA INDEX
Overall message
Ephemeris, Clock
at 15-min intervals
EDC, CDC
URA INDEX
L2C
L5
L1C
at 5-min intervals
at 5-min intervals
at 5-min intervals
at 30-s intervals
at 48-s intervals
at 24-s intervals
at 18-s intervals
Figure 3.1.2-3 An example of uplink timing of the navigation message
3.1.2.1.3 Uplink of "Alert" Flag, URA, Health Data and Differential Data
The “Alert” flag, URA, Health data and differential data described below are transmitted to the user by QZSS on the L1C/A, L1C, L2C, L5 and LEX signals. See Section 5.4 for information regarding the L1-SAIF signal. 3.1.2.1.3.1 "Alert" flag (on L1C/A, L1C, L2C, L5 and LEX)
QZSS monitors QZS signals and status and, once per second, makes a determination as to whether or not the Signal-In-Space (SIS) accuracy of any QZS signal is worse than 9.65 [m] and whether there is any detected problem with the QZS. If the determination is that a QZS signal is not suitable for use, the user is notified within the time limits specified for each signal in Section 4.3.2.2, of the detection of the problem via the corresponding “Alert” flag. Also when the QZS is in its maintenance operations which are described in Section 3.1.2.2.1.1 and Section 3.1.2.2.1.2, the “Alert” flag in its navigation message is set to indicate it to users and to notify to users that the QZS signal cannot be used.
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3.1.2.1.3.2 URA (on L1C/A, L1C, L2C, L5 and LEX)
URA stands for "User Range Accuracy”. The SIS accuracy, quantified as URA, is reported in a timely manner when the Ephemeris data being provided to the user and the SV clock parameters are used. QZSS monitors the QZS signals and, once per second, estimates the SIS accuracy of the signals in the direction of the QZS Line of Sight vector. The data are uploaded to the QZS within the time limits specified for each signal in Section 4.3.2.2, and the absolute value of the estimated URA (SIS accuracy) will be sent to the user within 30 seconds of the corresponding QZS signal transmission from MCS.
3.1.2.1.3.3 Health Data (on L1C/A, L1C, L2C, L5 and LEX)
QZSS monitors the QZS signals and QZS status and, once per second, makes a determination as to power level, modulation status and whether or not any message errors have occurred. At the same time, QZSS also monitors the signals of SVs of other GNSS systems and judges power level and modulation status, and, once per second estimates the SIS accuracy of these signals. The data are uploaded to the QZS immediately at the time when abnormal events are detected or confirmed that events are ended and return to nominal condition, therefore the users will be notified of the results within the seconds, which is specified in Section 4.3.2.2, of the corresponding QZS and other SV signal transmissions.
3.1.2.1.3.4 NMCT (on L1C/A), EDC and CDC (on L1C, L2C and L5)
NMCT stands for "Navigation Message Correction Table”. EDC stands for "Ephemeris Differential Correction”. CDC stands for "Clock Differential Correction”. By using the differential data provided by QZSS in these three correction terms, user receivers are able to mathematically remove most of the errors inherent in the Ephemeris data and SV clock parameters. QZSS monitors the QZS signals and the signals of other GNSS systems and, once per second, estimates the SIS error in the direction of the Line of Sight vector. The results of these estimates are uploaded to the QZS every 30 seconds for NMCT, and 300 seconds for EDC and CDC, as differential data.
3.1.2.1.3.5 UDRA and UDRAdtd
(on L1C, L2C and L5)
UDRA stands for "User Differential Range Accuracy". This value is used together with its
time derivative, UDRAdtd
, to enable users to determine the SIS accuracy after correction
with the EDC and CDC. This indicates the accuracy of the SIS error estimates calculated by the QZSS MCS in the direction of the Line of Sight vector for QZS signals and the signals of other GNSS systems. The value is uploaded to the QZS every 300 seconds.
3.1.2.1.3.6 NSC switching
NSC stands for "Non-Standard Code". The NSC is an invalid pseudo-random noise (PRN) code sequence (i.e., one that is not valid for use by any GNSS receiver). An operator of QZSS may switch manually from transmitting its normal ranging PRN code to transmitting the NSC to protect users under a system error. At such times, the transmission of NSC will ensure that users are not able to receive signals
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from the affected QZS. The time to switch to NSC from standard PRN code is within 15 seconds.
URA broadcast
Error Occurs
/maintenance
Alert flag
broadcast
investigation
Switch to NSC
・URA exceeds value which is assured in this specification
(Automatically)
・Actual URA exceeds index which has been broadcasted (Automatically)
・SIS accuracy exceeds the range by the URA’s bit length (Automatically)
・The QZS can not be used because of the maintenance (Manually)
・If corrected→Alert canceled (Manually)
・If corrected→Alert canceled (Manually), switch to standard code(Manually)
・If not corrected→broadcast suspended (Manually)
・O
ther
sys
tem
err
or h
as o
ccur
red
(Man
ually
)
investigation
URA broadcast
Error Occurs
/maintenance
Alert flag
broadcast
investigation
Switch to NSC
・URA exceeds value which is assured in this specification
(Automatically)
・Actual URA exceeds index which has been broadcasted (Automatically)
・SIS accuracy exceeds the range by the URA’s bit length (Automatically)
・The QZS can not be used because of the maintenance (Manually)
・If corrected→Alert canceled (Manually)
・If corrected→Alert canceled (Manually), switch to standard code(Manually)
・If not corrected→broadcast suspended (Manually)
・O
ther
sys
tem
err
or h
as o
ccur
red
(Man
ually
)
investigation
Figure 3.1.2-4 Relationship between "Alert" flag and URA/NSC switching
3.1.2.2 Maintenance, Failure, Restoration and Testing
3.1.2.2.1 Satellite System Maintenance
Two or more QZS will never halt service at the same time due to the orbit maintenance or attitude maintenance described below.
3.1.2.2.1.1 Orbit Maintenance
The QZS orbit is affected by forces of various types (the Earth's gravitation, the solar radiation and etc.). As a result, it will slowly drift from its intended orbit. For this reason, QZSS conducts orbit maintenance once every 150 days (average). Service is halted for up to two days during orbit maintenance. The notification way of the orbit maintenance information to the users are referred to chapter 7.2.1. Moreover, immediately prior to orbit maintenance, the "Alert" flag is set to "1". When orbit maintenance is complete, the "Alert" flag is cleared (set to “0”). As a result of orbit maintenance, the QZS orbit will be maintained within the range shown in Figure 3.1.2-5.
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Figure 3.1.2-5 Range of Orbital Maintenance
3.1.2.2.1.2 Momentum Management
The attitude of the QZS is affected primarily by the solar radiation pressure. The solar radiation pressure is absorbed by reaction wheels on the QZS to prevent it from affecting the QZS attitude. However, once per more than 30 days (average 40 days), momentum management (in which this angular momentum is unloaded) must be performed. During this momentum unloading process, service will be halted for a period of up to one day. Users will be notified in advance regarding the occurrence of the unloading process through the medium of the Internet, etc. Moreover, immediately before unloading, the "Alert" flag is set to "1". When unloading is complete, the "Alert" flag is cleared (set to “0”).
3.1.2.2.1.3 QZS failure and restoration
In the event that a certain QZS experiences an unexpected satellite-wide failure, notification of the failure of that QZS is sent from another QZS by means of the Navigation message (see Section 5.1.2.1.3). Transmission of the QZS signals from the failed QZS is halted or switched over to NSC. In the event that one of the sub-systems in a certain QZS fails, notification of the failure and repair of that sub-system is sent by means of the Navigation message (see Section 5.1.2.1.3) using signals that include identification of any remaining valid signals of that QZS. In addition, users are notified regarding the status of these systems through the medium of the Internet, etc shown in Section 7 of “PROVISION OF QZSS OPERATIONAL INFORMATION AND DATA VIA THE INTERNET”.
3.1.2.2.2 Ground Segment system maintenance
Ground Segment maintenance will be performed in a manner that does not adversely affect QZSS availability.
: Nominal (See Section 3.1.1.1.2)
: Nominal longitude of ascending
+/- 5[deg.]
: Nominal Inclination +/- 4[deg.]
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3.1.2.2.3 Testing
Depending on the nature of the tests, it may not always be possible to provide the specified
positioning performance to users during certain QZSS tests. At such times, the standard
transmitted PRN codes may be switched to NSC in order to protect users. In such cases, users
will generally be given advance notice through the medium of the Internet, etc shown in Section
7 of “PROVISION OF QZSS OPERATIONAL INFORMATION AND DATA VIA THE
INTERNET” regarding the period of time during which such testing will occur.
3.1.3 Signals transmitted by QZS = QZS Signals
3.1.3.1 Types of Signals Transmitted by QZS
QZSS satellites transmit six positioning signals: L1C/A signal, L1-SAIF signal, L1C signal, L2C
signal, LEX signal and L5 signal. Four of these -- L1C/A, L1C, L2C and L5 -- are known as
positioning availability enhancement signals (or simply availability enhancement signals) in the
sense that they complement the existing Global Navigation Satellite System (GNSS). The
remaining two signals -- L1-SAIF and LEX -- are known as positioning performance enhancement
signals (or simply performance enhancement signals) in the sense that they enhance performance
through the transmission of existing GNSS differential data and integrity data concerning GNSS
signals as determined by QZSS.
3.1.3.2 Spectrum of QZS Signals
The six positioning signals transmitted by QZS have four center frequencies. With the reference
frequency set to MHzf 23.100 , these carrier frequencies are 0154 f for L1, 0125 f
for LEX, 0120 f for L2, 0115 f for L5.
Figure 3.1.3-1 shows the power spectral density of the six QZS signals versus frequency. Note that
this is the power spectral density at the input of user antenna on the ground.
-260
-255
-250
-245
-240
-235
-230
-225
-220
-215
1125.30 1176.45 1227.60 1278.75 1329.90 1381.05 1432.20
-260
-255
-250
-245
-240
-235
-230
-225
-220
-215
1329.90 1381.05 1432.20 1483.35 1534.50 1585.65 1636.80
Frequency (MHz)
Pow
er
Spectr
alD
ensity (
dB(W
/Hz))
Figure 3.1.3-1 Power Spectral Density of QZS Signals
L5 L2C
LEX L1C
L1C/A
L1-SAIF
L5 center frequency: 1176.45 MHz
L2 center frequency: 1227.60 MHz
LEX center frequency: 1278.5 MHz
L1 center frequency: 1575.42 MHz
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3.1.3.3 General Specifications for QZS Signals
Table 3.1.3-1 shows the general specifications for QZS signals.
Table 3.1.3-1 General Specifications for QZS Signals
Signal name Center frequency I/Q channel
identification
Spreading
frequency
L1C/A *
1575.42MHz
- 0.1 f0
L1C * Data channel 0.1 f0
Pilot channel 0.1 f0
L1-SAIF - 0.1 f0
L2C * 1227.60MHz
-
(2 channels time
multiplexed)
0.1 f0
L5 * 1176.45MHz I channel 1 f0
Q channel 1 f0
LEX 1278.75MHz -
0.5 f0
*GPS availability enhancement signal
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3.1.3.4 QZS Signal Doppler
The Doppler values for QZS signals received at eight reference locations equals to Relative velocity of signals (Change rate of distance) between each city and QZS-1 (shown in Figure 3.1.3-2) multiplied by the Doppler coefficients for each positioning signal frequency (Center frequency/Speed of light) (listed in Table 3.1.3-2). In Figure 3.1.3-2, the gaps in the plots of relative velocity correspond to times when the QZS is below 10 degrees elevation angle for the corresponding location. The upper and lower solid lines represent the upper and lower ranges of the relative velocity, respectively.
-600
-400
-200
0
200
400
600
0 3 6 9 12 15 18 21 24
Rela
tive
Velo
city
(m/se
c)
Time (Hr)
-600
-400
-200
0
200
400
600
0 3 6 9 12 15 18 21 24
Rela
tive
Velo
city
(m/se
c)
Time (Hr) Wakkanai (Hokkaido, Japan) Tokyo
-600
-400
-200
0
200
400
600
0 3 6 9 12 15 18 21 24
Rela
tive
Velo
city
(m/se
c)
Time (Hr)
-600
-400
-200
0
200
400
600
0 3 6 9 12 15 18 21 24
Rela
tive
Velo
city
(m/se
c)
Time (Hr) Okinawa Seoul
-600
-400
-200
0
200
400
600
0 3 6 9 12 15 18 21 24
Rela
tive
Velo
city
(m/se
c)
Time (Hr)
-600
-400
-200
0
200
400
600
0 3 6 9 12 15 18 21 24
Rela
tive
Velo
city
(m/se
c)
Time (Hr) Bangkok Singapore
-600
-400
-200
0
200
400
600
0 3 6 9 12 15 18 21 24
Rela
tive
Velo
city
(m/se
c)
Time (Hr)
-600
-400
-200
0
200
400
600
0 3 6 9 12 15 18 21 24
Rela
tive
Velo
city
(m/se
c)
Time (Hr) Sydney Perth
Figure 3.1.3-2 Relative velocity of signals (Change rate of distance) between each city and QZS-1 (See Table 3.1.1-1 for calculation condition. Observation EPOCH = 2009/Dec/26/12:00UTC. Horizontal axis
means elapsed time from EPOCH.)
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Table 3.1.3-2 Doppler coefficients for signals Signal Doppler scale
L1C/A, L1C, L1-SAIF 5.3
L2C 4.1
L5 3.9
LEX 4.3
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3.1.3.5 Elevation and Azimuthal Angles
Plots of angle of elevation and azimuth angles to QZS for eight reference locations are shown in Figure 3.1.3-3 as they vary over the course of the QZS orbit.
60
30
10
EW
N
S
60
30
10
EW
N
S Wakkanai (Hokkaido, Japan) Tokyo
60
30
10
EW
N
S
60
30
10
EW
N
S Okinawa Seoul
60
30
10
EW
N
S
60
30
10
EW
N
S Bangkok Singapore
60
30
10
EW
N
S
60
30
10
EW
N
S Sydney Perth
Figure 3.1.3-3 Elevation and Azimuthal angles for each city (See Table 3.1.1-1 for calculation condition. Observation EPOCH = 2009/Dec/26/12:00 UTC)
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3.1.3.6 Received Signal Power Level at Reference Locations
The User Received Power Levels for each QZS signal at eight reference locations are shown in Figure 3.1.3-4 as a function of time as they vary over the course of the QZS orbit. In Figure 3.1.3-4, the gaps in the plots of signal power correspond to times when the QZS is below 10 degrees elevation angle for the corresponding location.
-162
-160
-158
-156
-154
-152
-150
0 3 6 9 12 15 18 21 24
UR
P (dB
W)
Time (Hr)
L5
LEX
SAIF
L1C
L1C/A
L2C
-162
-160
-158
-156
-154
-152
-150
0 3 6 9 12 15 18 21 24
UR
P (dB
W)
Time (Hr)
L5
LEX
SAIF
L1C
L1C/A
L2C
Wakkanai (Hokkaido, Japan) Tokyo
-162
-160
-158
-156
-154
-152
-150
0 3 6 9 12 15 18 21 24
UR
P (dB
W)
Time (Hr)
L1C/A
L2C
L5
LEX
SAIF
L1C
-162
-160
-158
-156
-154
-152
-150
0 3 6 9 12 15 18 21 24
UR
P (dB
W)
Time (Hr)
L5
LEX
SAIF
L1C
L1C/A
L2C
Okinawa Seoul
-162
-160
-158
-156
-154
-152
-150
0 3 6 9 12 15 18 21 24
UR
P (dB
W)
Time (Hr)
L5
LEX
L1C/A
L2C
SAIF
L1C
-162
-160
-158
-156
-154
-152
-150
0 3 6 9 12 15 18 21 24
UR
P (dB
W)
Time (Hr)
L5
LEX
SAIF
L1C
L1C/A
L2C
Bangkok Singapore
-162
-160
-158
-156
-154
-152
-150
0 3 6 9 12 15 18 21 24
UR
P (dB
W)
Time (Hr)
L5
LEX
SAIF
L1C
L1C/A
L2C
-162
-160
-158
-156
-154
-152
-150
0 3 6 9 12 15 18 21 24
UR
P (dB
W)
Time (Hr)
L5
LEX
SAIF
L1C
L1C/A
L2C
Sydney Perth
Figure 3.1.3-4 Changes of received signal power level for each city (See Table 3.1.1-1 for calculation condition. Observation EPOCH = 2009/Dec/26/ 12:00 UTC. Horizontal axis means elapsed time from
EPOCH.)
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3.1.4 Time System and Coordinate System
3.1.4.1 Time System
The QZSS time system is called QZSST and has the following characteristics. QZSST conforms to UTC (NICT) and the offset with respect to the GPS time system, GPST, is controlled.
(1) One-second length The length of one second is identical to International Atomic Time (TAI). It is also the same for GPS and Galileo.
(2) Integer second offset for TAI The integer second offset for TAI is the same as for GPS and TAI is always 19 seconds ahead of QZSST.
(3) Starting point of Week Number for QZSST The starting point of the Week Number for QZSST is identical to GPST. Therefore, this parameter is just referred to as “Week Number” (and not specified as corresponding to QZSST or GPST).
3.1.4.2 Coordinate System
The QZSS geodetic coordinate system is known as the Japan satellite navigation Geodetic System (JGS). This coordinate system is defined as follows so as to approach the International Terrestrial Reference System (ITRS).
(a) Origin: Same as defined for the GRS803 ellipsoid (earth’s center of mass)
The geometrical center of the GRS80 ellipsoid is established as the Earth’s
center of mass.
(b) Z axis: International Earth Rotation and Reference Systems Service (IERS4) pole
direction
(c) X-axis: Direction of intersection of Greenwich Meridian and equatorial plane
containing origin and Z-axis
(d) Y-axis: Direction formed by the right-handed fixed geocentric coordinate system
3 Background: Abbreviation for Geodetic Reference System 1980. GRS80 defines the shape of the earth, gravitational constants, angular velocity and other physical constants and computational expressions that were adopted in 1979 by the International Association of Geodesy (IAG) and the International Union of Geodesy and Geophysics (IUGG). In GRS80, the shape of the ellipsoid, the direction of axes and the earth’s center of gravity were established and define a reference ellipsoid known as the GRS80 ellipsoid.
4 Background: Abbreviation for International Earth Rotation and Reference Systems Service. IERS is an international organization formed with the objective of defining and maintaining a common global standard coordinate system, determining global time and so on. Its parent organizations are the International Union of Geodesy and Geophysics (IUGG) and the International Association of Geodesy (IAG).
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3.2 Interface with Other Systems
3.2.1 QZSS Time System Relative to Other GNSS
3.2.1.1 Interface with GPS
The SV clocks for QZS and GPS satellites are both controlled with respect to the offset from the
GPS time scale (GPST). The size of the offset is corrected by the SV clock parameter included in
the Navigation message that is transmitted by each satellite.
3.2.1.2 Interface with Galileo
TBD
GALILEO satellites’ Clocks
UTC
GPST(GPS-TIME)
TAI Steered <50ns,28ns(2-sigma)
Ste
ere
d
<5
0ns (m
odulo
1 s
)
UTC(USNO)
GGTObroadcasted on both GPS-L1C and GALILEO
GPS SV Clock relative to GPSTbroadcasted on GPS signal
GALILEO SV Clock relative to GSTbroadcasted on GALILEO signal
UTC(NICT)
GST(GALILEO-TIME)QZSST(QZS-TIME)
GPS satellites’ Clocks
QZS satellites’ Clocks
QZS SV Clock relative to GPSTbroadcasted on QZS signal
<5
ns(2
-sig
ma
)
No
rma
lized fre
que
ncy
accura
cy G
ST
rela
tive
to
UT
C <
3 x
10
-̂13 0s
19s
Figure 3.2.1-1 Diagram of Time System Relationships between QZSS, GPS and Galileo
3.2.2 QZSS Coordinate System Relative to Other GNSS
The GPS coordinate system (WGS84) and the Galileo coordinate system have been prepared so as to
approach ITRS. Accordingly, under the definition of JGS in Section 3.1.4, all systems are operated
so the differences are maintained as specified in Section 4.3.3.2.2.
Figure 3.2.2-1 shows a conceptual diagram of the relationships between past and future geodetic
coordinate systems. Note that as time moves on, all systems are expected to converge toward ITRS.
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ITRSITRS
ITRF xxITRF xx
WGS84WGS84
QZSS FrameQZSS Frame
Galileo FrameGalileo Frame
timedif
fere
nce
ITRSITRS
ITRF xxITRF xx
WGS84WGS84
QZSS FrameQZSS Frame
Galileo FrameGalileo Frame
timedif
fere
nce
Figure 3.2.2-1 Convergence of Geodetic Coordinate Systems
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4 QZSS Coverage, Availability and Performance
4.1 QZSS Service Area
4.1.1 Single QZS Coverage Area
Figure 4.1.1-1 and Figure 4.1.1-2 show the availability (the percentage of time during which the specified minimum elevation angle condition is fulfilled) of a single QZS satellite across the surface of the Earth.
Figure 4.1.1-1 Percentage of Time during which a Single QZS can be seen at an Elevation Angle of 10° or
more
Figure 4.1.1-2 Percentage of Time during which a Single QZS can be seen at an Elevation Angle of 60° or
more
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4.1.2 QZSS Coverage Area
Figure 4.1.2-1 and Figure 4.1.2-2 show the availability (the percentage of time during which the specified minimum elevation angle condition is fulfilled) of a single QZS across the surface of the Earth due to the QZSS constellation. For the 3-satellite QZSS constellation, at least one QZS is available 100% of the time not only in Japan but in almost all parts of Southeast Asia and Oceania at an elevation angle of 10° or more. In Japan, at least one QZS is available 100% of the time at an elevation angle of 60° or more.
Figure 4.1.2-1 Percentage of Time during which at least One QZS in the 3-satellite QZSS constellation can
be seen at an Elevation Angle of 10° or more
Figure 4.1.2-2 Percentage of Time during which at least One QZS in the 3-satellite QZSS constellation can
be seen at an Elevation Angle of 60° or more
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4.1.3 Elevation Angle Variation for QZSS Constellation
The variation of QZS elevation angles for the 3-satellite QZSS constellation at eight reference locations is shown in Figure 4.1.3-1 as a function of time as they vary over the course of the QZS orbit.
QZSS Elevation Angle Profile @Wakkanai
0
10
20
30
40
50
60
70
80
90
0 3 6 9 12 15 18 21 24Time(Hr)
Ele
vation A
ngl
e (de
g)
QZS1QZS2QZS3
QZSS Elevation Angle Profile @Tokyo
0
10
20
30
40
50
60
70
80
90
0 3 6 9 12 15 18 21 24Time(Hr)
Ele
vation
Ang
le (de
g) QZS1QZS2QZS3
Wakkanai (Hokkaido, Japan) Tokyo
QZSS Elevation Angle Profile @Okinawa
0
10
20
30
40
50
60
70
80
90
0 3 6 9 12 15 18 21 24Time(Hr)
Ele
vation
Ang
le (de
g)
QZS1QZS2QZS3
QZSS Elevation Angle Profile @Soul
0
10
20
30
40
50
60
70
80
90
0 3 6 9 12 15 18 21 24Time(Hr)
Ele
vation
Ang
le (de
g) QZS1QZS2QZS3
Okinawa Seoul
QZSS Elevation Angle Profile @Bangkok
0
10
20
30
40
50
60
70
80
90
0 3 6 9 12 15 18 21 24Time(Hr)
Ele
vation
Ang
le (de
g)
QZS1QZS2QZS3
QZSS Elevation Angle Profile @Singapore
0
10
20
30
40
50
60
70
80
90
0 3 6 9 12 15 18 21 24Time(Hr)
Ele
vation
Ang
le (de
g)
QZS1QZS2QZS3
Bangkok Singapore
QZSS Elevation Angle Profile @Sydney
0
10
20
30
40
50
60
70
80
90
0 3 6 9 12 15 18 21 24Time(Hr)
Ele
vation
Ang
le (de
g)
QZS1QZS2QZS3
QZSS Elevation Angle Profile @Perth
0
10
20
30
40
50
60
70
80
90
0 3 6 9 12 15 18 21 24Time(Hr)
Ele
vation
Ang
le (de
g)
QZS1QZS2QZS3
Sydney Perth
Figure 4.1.3-1 Variation of QZSS Constellation (for 3 satellites) Elevation Angles for eight cities (See Table 3.1.1-1 for calculation condition of QZS-1. For QZS-2 and 3, we assumed the right ascension of
ascending node is +/- 120 deg from that value of QZS-1. Observation EPOCH = 2009/Dec/26/12:00UTC Horizontal axis means elapsed time from EPOCH.)
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4.1.4 QZSS constellation availability
For the 3-satellite QZSS constellation, Figure 4.1.4-1 shows the average number of QZS satellites visible from the Earth’s surface. Note that two or more satellites are always visible not only from Japan but also from virtually every region of Southeast Asia and Oceania as well.
Figure 4.1.4-1 Average Number of QZS Satellites that can be seen at an Elevation Angle of 10° or more
with the 3-satellite QZSS Constellation
4.1.5 Target Regions for Ionospheric Parameters Transmitted by QZS
Each QZS transmits ionospheric parameters that are effective in the geographical regions shown in Figure 4.1.5-1. The accuracy of these parameters is detailed in Section 4.3.3.3. These ionospheric parameters should not be used in regions other than those target regions shown in Figure 4.1.5-1. Instead, ionospheric parameters transmitted by GPS, or GPS ionospheric parameters retransmitted by the QZS should be used outside of the target regions.
Figure 4.1.5-1 Target Regions for Ionospheric Parameters Transmitted by QZS
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4.1.6 Availability Improvement when QZSS and Galileo are Combined with GPS
Figure 4.1.6-1 (1/2) and Figure 4.1.6-1 (2/2) show the improvement in GNSS availability when QZSS and Galileo are combined with the existing GPS constellation (as of NOV 2006). Each of the two figures includes the cases of GPS alone, GPS with QZSS and GPS with QZSS and Galileo. Figure 4.1.6-1 (1/2) and Figure 4.1.6-1 (2/2) provide plots of the percentage of time when the Position Dilution of Precision (PDOP) is less than 6 for GNSS receiver mask angles of 20° and 40°, respectively. Figure 4.1.6-2 show the average number of visible satellites for GNSS receiver mask angles of 10°, 20° and 40°, respectively.
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GPS (mask angle 20°)
QZS + GPS (mask angle 20°)
QZS + GPS + Galileo (mask angle 20°)
Figure 4.1.6-1(1/2) Percentage of Time when PDOP < 6 for an Elevation Angle Mask of 20°
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GPS (mask angle 40°)
QZS + GPS (mask angle 40°)
QZS + GPS + Galileo (mask angle 40°)
Figure 4.1.6-1(2/2) Percentage of Time when PDOP < 6 for an Elevation Angle Mask of 40°
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GPS (mask angle 10°)
QZS + GPS (mask angle 10°)
QZS + GPS + Galileo (mask angle 10°)
Figure 4.1.6-2 (1/3) Average Number of Visible Satellites for an Elevation Angle Mask of 10°
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20G
GPS (mask angle 20°) 20QG
QZS + GPS (mask angle 20°) 20QGG
QZS + GPS + Galileo (mask angle 20°)
Figure 4.1.6-2 (2/3) Average Number of Visible Satellites for an Elevation Angle Mask of 20°
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40G
GPS (mask angle 40°) 40QG
QZS + GPS (mask angle 40°) 40QGG
QZS + GPS + Galileo (mask angle 40°)
Figure 4.1.6-2 (3/3) Average Number of Visible Satellites for an Elevation Angle Mask of 40°
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4.2 Service Availability Each QZS transmits positioning signals 24 hours a day, 365 days a year. However, the time of day during which a particular QZS satellite is visible to a given location varies with the date.
4.2.1 The fixed initial right ascension of ascending node depending on the launch time
Because the initial right ascension of ascending node was fixed depending on the exact launch time, the visibility time was also fixed after the launch. For orbital calculation after the QZS-1 launch, the longitude of the ascending node at weekly epoch would be published as a QZSS almanac via "QZSS Website for Operational Information and Data" in Section 7.1. The visibility time from each location can be seen in Figure 4.2.1-1 (the right ascension of ascending node is 195 [deg]).
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0 9
JST
2012
Mar
2012
Apr
9
7
5
3
1
23
21
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
UTC
19
17
15
13
11
8
4
2
6
12
10
24
22
20
18
16
14
UTC
24
22
20
18
16
14
12
10 19
17
15
13
11
8
4
2
6
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
JST
2012
Mar
2012
Apr
9
7
5
3
1
23
21
0 9
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
2012
Mar
2012
Apr
Wakkanai (Hokkaido, Japan) Tokyo
JST
2012
Mar
2012
Apr
9
7
5
3
1
23
21
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
UTC
19
17
15
13
11
8
4
2
6
12
10
24
22
20
18
16
14
0 9
2012
Mar
2012
Apr
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
JST
2012
Mar
2012
Apr
9
7
5
3
1
23
21
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
UTC
19
17
15
13
11
8
4
2
6
12
10
24
22
20
18
16
14
0 9
2012
Mar
2012
Apr
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
Okinawa Seoul
JST
2012
Mar
2012
Apr
9
7
5
3
1
23
21
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
UTC
19
17
15
13
11
8
4
2
6
12
10
24
22
20
18
16
14
0 9
2012
Mar
2012
Apr
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
JST
2012
Mar
2012
Apr
9
7
5
3
1
23
21
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
UTC
19
17
15
13
11
8
4
2
6
12
10
24
22
20
18
16
14
0 920
12 M
ar
2012
Apr
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
Bangkok Singapore
12
10
24
22
20
18
16
14
UTC
19
17
15
13
11
8
4
2
6
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
JST
2012
Mar
2012
Apr
9
7
5
3
1
23
21
0 9
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
2012
Mar
2012
Apr
JST
2012
Mar
2012
Apr
9
7
5
3
1
23
21
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
UTC
19
17
15
13
11
8
4
2
6
12
10
24
22
20
18
16
14
0 9
2012
Mar
2012
Apr
2011
Jun
2011
Jul
2011
Aug
2011
Sep
2011
Oct
2012
May
2011
Nov
2011
Dec
2012
Jan
2012
Feb
Sydney Perth
Figure 4.2.1-1 Initial Single-satellite QZSS Visibility Time for eight Reference Locations. (See Table 3.1.1-1 for calculation condition. Dark shaded areas represent elevation angles of 60[deg] or more; light
blue areas represent elevation angles of 10[deg] to 60[deg] and white is less than 10[deg]; vertical scale is hours on UTC and JST.)
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4.3 System Performance
4.3.1 Availability
4.3.1.1 QZSS Availability in the case of a Single Satellite
With regard to the transmission of availability enhancement signals, QZSS availability (the percentage of the normal use signal in visibility time (10 degrees elevation angle or higher)) in the case of a single satellite shall be 95% or better. With regard to the transmission of performance enhancement signals (L1-SAIF signal), availability shall be 95% or better. As to LEX signal, specific value on the availability is not defined during the demonstration phase.
4.3.1.2 QZSS Availability in the case of a 3-satellite constellation
TBD
4.3.2 Alert flag, URA and Health Data
4.3.2.1 Notification of Alert flag, URA and Health Data
Data relating to the status of the QZS signals and other GNSS systems’ signals are sent to the user by means of the "Alert" flag, URA and health data. “Alert” flag will set to “1” in the case that SIS accuracy exceeds 9.65 [m] or other troubles for QZS happens (Default case: “Alert“ flag=”0”).
4.3.2.2 Maximum Notification Times
The maximum notification times relating to URA, the "Alert" flag, and health data are defined as the worst case (longest) time required from the moment of detecting anomaly by a QZSS Monitor Station until the total notification message arrives at the user's antenna input terminal. Figure 4.3.2-1 shows the maximum notification times for “Alert” flag, URA, Health data and integrity data.
4.3.2.3 False Alarm Probability
The probability that the "Alert" flag will be erroneously set to "1" (even though the corresponding QZS signal is normal and can be used) shall be 1x10-6or less.
4.3.2.4 Mis-Detection Probability
The probability that the "Alert" flag will erroneously not be set to "1" (even though an error has occurred with respect to the QZS signal and the signal should not be used) shall be 1x10-3 or less.
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Integrity data notification time
L1C
0(Event Occurrence)
time
50 100 150 200 250 300
Alert
URA
Health (Subframe 1)
Health (Subframe 4,5)※
30s
60s
90s
900s
L1C/A
Alert (L1C Health)
URA
Health※
90s
Alert
URA
Health (MSG Type 10)
Health (MSG Type 53) ※
L2C
40s
70s
90s
240s
Alert
URA
Health (MSG Type 10)
Health (MSG Type 53) ※
L560s
90s
240s
UDREI 24sL1-SAIF
LEX
Alert
URA
Health
90s
240s
30s
24s
24s
400s
※Target is the health information of Other GNSS systems
Figure 4.3.2-1 “Alert” flag, URA, Health Data and Integrity Data Maximum Notification Time
4.3.2.5 L1-SAIF Signal Specifications
The appropriate protection level shall be computed within 30 seconds by user receivers at any location in the service area even when an error condition occurs. The probability of the user positioning error exceeding the protection level shall be 0.00001/hour or less.
4.3.3 Accuracy
4.3.3.1 SIS Accuracy provided by QZSS Availability Enhancement Signals
The SIS accuracy provided by all QZS signals (except the L1-SAIF and LEX signals) shall be such that the URA will not exceed 2.60 [m] with a probability of 95% or better including the error of the time systems’ offset and the coordinate systems’ offset between QZSS and GPS.
4.3.3.2 Accuracy of Interoperability with Existing GNSS
4.3.3.2.1 Time System Offset
The QZSS time scale offset from GPS time shall not exceed 2.0 [m] (about 6.67 [ns]) with a probability of 95% or better. The QZSS time scale offset from Galileo shall not exceed TBD [m] (TBD [ns]) with a probability of 95% or better.
4.3.3.2.2 Coordinate System Offset
The QZSS coordinate system offset from GPS and Galileo shall be 0.02 [m] or less
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4.3.3.3 Accuracy of Ionospheric Parameters
The accuracy available from the ionospheric parameters transmitted by the QZS shall be such that user receivers in the regions indicated in Section 4.1.5 will be able to correct the associated range measurements to within 14.0 [m] or better, with the exception of intervals during large ionospheric disturbances. A “large ionospheric disturbance” occurs when the ionospheric delay exceed TBD[m] (about 5% in a year).
4.3.3.4 Positioning Accuracy by means of Availability Enhancement Signals
The horizontal positioning accuracy shown in Table 4.3.3-1 shall be provided 95% of the time or more, through QZS signals (except L1-SAIF and LEX signals) used in combination with GPS signals, assuming all signals arrive at 10 degrees elevation angle or higher.
Table 4.3.3-1 Positioning Accuracy by means of Availability Enhancement Signals Horizontal Positioning accuracy Notes
Equivalent to modernized GPS signal (horizontal
positioning accuracy 95%)
Single frequency: 21.9 m
Dual frequency: 7.5 m
Single frequency (user ranging error: 7.3 m)
Dual frequency (user ranging error: 2.5 m)
4.3.3.5 Positioning Accuracy by means of Performance Enhancement Signals
The positioning accuracy shown in Table 4.3.3-2 shall be achievable with the QZSS L1-SAIF signal, except in cases of large multipath error or a large ionospheric disturbance.
Table 4.3.3-2 Positioning Accuracy by means of Performance Enhancement Signals Positioning accuracy Notes
Submeter class: 1 m (rms)
(wide-area DGPS performance enhancement)
L1-SAIF signal use
more than 5 degree elevation angle
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5 QZSS Signal Properties
QZSS provides six types of signals to users.
Section 5.1 describes the fundamental properties of all QZS signals. Subsequent sections provide details
such as the signal configuration, carrier wave properties, code properties and navigation message
configuration and content for each of the six signals transmitted by QZS satellites.
5.1 QZS Power Levels, Bandwidths and Center Frequencies All QZS signals are right-hand circularly polarized spread spectrum signals. Table 5.1-1 shows the center frequencies, bandwidths and received minimum power levels of these signals. After being superimposed with a navigation message, the baseband QZS signals are modulated with a spread spectrum pseudorandom noise (PRN) code and then up-converted by an RF carrier at the indicated center frequency.
Table 5.1-1 QZS signal specifications
Signal name I/Q channel
identification Center frequency
Frequency
Bandwidth
Received
Minimum Power Level*
L1C/A L1CA
1575.42 MHz
24.0 MHz
(±12.0 MHz) -158.5 dBW
L1C L1CD 24.0 MHz
(±12.0 MHz)
-163.0 dBW -157.0 dBW
(Total) L1CP -158.25 dBW
L1-SAIF - 24.0 MHz
(±12.0 MHz) -161.0 dBW
L2C - 1227.60 MHz 24.0 MHz
(±12.0 MHz)
-160.0 dBW
(total)
L5
L5I
1176.45 MHz
24.9 MHz
(±12.45 MHz) -157.9 dBW
-154.9 dBW
(Total) L5Q
24.9 MHz
(±12.45 MHz) -157.9 dBW
LEX - 1278.75 MHz 39.0 MHz
(±19.5 MHz)
-155.7 dBW
(total)
*: this is defined in Section 5.1.1.8.
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5.1.1 Overview of signal properties
5.1.1.1 QZS Signal configuration
Table 5.1.1-1 shows a summary of the ranging code, modulation method and navigation message structure for each of the QZS signals.
Table 5.1.1-1 Configuration of QZS signals Signal name
(abbreviation)
Channel
identification Ranging code and modulation method Navigational message
L1 si
gnal
s
L1C/A signal
(QZS-L1)
- One of the PRN codes for the GPS C/A signal
in Applicable Document (1).
Modulation method is BPSK (1).
Same data structure, bit rate and coding method
as the C/A signal in Applicable Documentation
(1) in Chapter 2; same type of navigation
message.
L1C signal
(QZS-L1C)
L1CD One of the PRN codes for the GPS PRN code
specified in Applicable Document (3).
Modulation method of QZS-1 is BOC (1, 1).
Modulation method of LIC signals after “Phase
Two” should be studied further if MBOC could
be adopted.
Same data structure, bit rate and coding method
as in Applicable Documentation (3) in Chapter
2; same type of navigation message.
L1CP Modulated using the same code sequence as the
overlay code in Applicable Documentation (3)
in Chapter 2.
L1-SAIF signal
(QZS-L1-SAIF)
- One of the PRN codes for the GPS C/A signal
in Applicable Document (1). Modulation
method is BPSK (1).
Same data structure, bit rate and coding method
as in Applicable Documentation (4) in Chapter
2; same type of navigation message.
L2C signal (QZS-L2C) - One of the PRN codes for the
GPS L2C signal in Applicable
Document (1). Modulation
method is BPSK (1).
L2C (CM)
code
Same type of Navigation message with the
same data structure, bit rate and coding
method as in Applicable Document (1).
L2C (CL)
code
Dataless (i.e., no data is modulated onto this
signal)
L5 signal (QZS-L5) I channel One of the PRN codes for the GPS L5 signal in
Applicable Document (2). Modulation method
is BPSK (10).
Same type of Navigation message with the
same data structure, bit rate and coding
method as in Applicable Document (2).
Q channel One of the PRN codes for the GPS L5 signal in
Applicable Document (2). Modulation method
is BPSK (10).
Dataless
LEX signal
(QZS-LEX)
- Small Kasami sequence.
Modulation method is BPSK
(5).
2 channels are obtained by chip
by chip time multiplexing.
Short code 2000 bits/frame At the beginning of the frame,
in addition to the preamble there is a type ID
that identifies the content of the frame. 250 sps
x 8 = 2 kbps by means of code-shift keying. A
Reed-Solomon code is added.
Long code Dataless
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5.1.1.1.1 Signal configuration of L1 signals
QZS transmits three signals using the L1 center frequency: the L1C/A signal, the L1C signal and the L1-SAIF signal. The L1 availability enhancement signals include two carrier waves (L1C/A、L1CD and L1CP) that are designed to maintain a specified phase relationship. The I-channel contains L1C/A and L1CD while the orthogonal Q-channel contains L1CP. The phase relationship specifications are given in Section 5.1.1.6.1. L1C/A, L1CD and L1CP are BPSK modulated with bit strings equivalent to the L1C/A signal, the L1C signal data channel, and the L1C signal pilot channel, respectively. When the L1CD modulation bit of QZS-1 is 0, the phase of the L1CD carrier wave is 0°. The L1CD carrier wave is 180° reversed when the L1CD modulation bit is 1. When the L1CP modulation bit is 1, the phase of the L1CP carrier wave is 90° advanced. When the L1CP modulation bit is 0, the phase of the L1CP carrier wave is 90° delayed. The phase relation of LI signal for QZS-1 is not same as GPS (Brock III) (Refer to Applicable Documents (3). L1CD and L1CP for QZS-1 are orthogonal each other at right angles, but L1CD and L1CP for GPS are in phase (Figure 5.1.1-1). The phase relation of LI signal for a satellite after “Phase Two” is under study.
L1CD、L1C/A
L1CP
QZS-1
L1CD、L1CP
L1C/A
GPS
Figure 5.1.1-1 Phase Relations of LI Signal for QZS-1 and GPS
5.1.1.1.2 L2C signal configuration
The L2C signal has a single carrier wave. This carrier wave is BPSK modulated using a certain bit string L2CC . This bit string is generated by two types of bit strings CMLC 2 , CLLC 2 (corresponding to two channels) that are selected alternately in a time-multiplexed manner.
5.1.1.1.3 L5 signal configuration
The L5 signal has two carrier waves that are orthogonal with respect to one another. The phase relationship specifications are given in Section 5.1.1.6.1. Each of these carrier waves is BPSK modulated by two types of bit strings L5I5C , L5Q5C (corresponding to the two channels). When the L5I modulation bit is 0, the phase of the L5I carrier wave is 0°. The L5I carrier wave is 180° reversed when the L5I modulation bit is 1. When the L5Q modulation bit is 1, the phase of the L5Q carrier wave is 90° advanced. When the L5Q modulation bit is 0, the phase of the L5Q carrier wave is 90° delayed.
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5.1.1.1.4 L1-SAIF signal configuration
The L1-SAIF signal has a single carrier wave. This carrier wave is BPSK modulated by a certain bit string L1SAIFC .
5.1.1.1.5 LEX signal configuration
The LEX signal has a single carrier wave. This carrier wave is BPSK modulated by a certain bit string LEXC . This bit string is generated by two types of bit strings LEXSC , LEXLC (corresponding to two channels) that are selected alternately in a time-multiplexed manner.
5.1.1.2 QZS Operational Frequency
The operational QZS frequency, fs, is offset with respect to the reference frequency of f0 = 10.23 MHz, in order to provide compensation for the relativistic effect to which the QZS satellites are subjected due to their orbital motion. The frequency is as follows:
HzHzffffs 994476823.102299991023000010399.511 10
00
Since the QZS orbits are elliptical, the impact of the relativistic effect will slowly fluctuate. However, the equations in Section 6.3.2 (2) can be used to compensate for this. In addition, the equations in Section 6.3.2 (1) with the SV clock parameters (af0, af1, af2,) included in the QZSS navigation messages can be used to compensate for the fluctuation of QZSST depended on other sources.
5.1.1.3 Correlation loss
Correlation loss is defined as the difference between the SV power received in the specified signal bandwidth (e.g., ± 12 MHz for the L1 carrier) and the signal power recovered in an ideal receiver of the same bandwidth, which perfectly correlates using an exact replica of the waveform within an ideal (sharp cut-off) bandpass filter with linear phase. For all QZSS signals, the correlation loss that occurs in the navigation payload of the QZS satellite shall not exceed 0.6 dB.
5.1.1.4 Carrier phase noise
For all QZSS signals, the spectral density of the phase noise for the unmodulated carrier wave (i.e., prior to modulation with the PRN code and navigation message) shall be such that a phase-locked loop (PLL) with single-sided bandwidth of 10 Hz will be able to track the carrier phase to an accuracy of 0.1 radians (RMS). Figure 5.1.1-2 shows the phase noise requirements for all QZSS signals in more detail.
-47 -47
-77
-94-101
-105-110
-120
-100
-80
-60
-40
-20
0
1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06
Offset Frequency (Hz)
Phas
e N
oise
Densi
ty (
dBc/H
z)
Figure 5.1.1-2 Phase Noise of all QZS signals
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5.1.1.5 Spurious characteristics
For all QZSS signals, in-band spurious transmissions shall be at least 40 dB below the power level
of the unmodulated carrier wave (i.e., prior to superposition of the PRN code and navigation
message).
5.1.1.6 Phase relationships among QZS signals
5.1.1.6.1 Phase orthogonal
The two carrier waves (L1CD and L1CP, L5I and L5Q) are maintained in a 90° orthogonal phase
relationship with one another. The variation in this phase relationship shall not exceed ± 5.0°.
5.1.1.6.2 Phase relationship of PRN code and carrier wave
The fluctuations in the difference between the Pseudo Random Noise (PRN) code phase and the
carrier wave phase at the antenna phase center for all QZS signals shall not exceed 1.2 ns.
Additionally, within any 30 s period, fluctuations in the difference between the PRN code phase
and the carrier wave phase shall not exceed 0.01 ns (equivalent to 0.3 cm ranging error).
5.1.1.6.3 PRN code jitter
5.1.1.6.3.1 PRN code jitter
The jitter, σjitter, of the PRN code zero-crossing interval (according to Figure 5.1.1-3) shall not
exceed 2.0 ns for a value of 3σ.
Complete, ideal PRN code
Realistic PRN code with edge jitter
σ jitter σ jitter σ jitter σ jitter σ jitter σ jitterσ jitter
Figure 5.1.1-3 Definition of code jitter σjitter
5.1.1.6.3.2 Delay in PRN code rising/falling edge
For the PRN code, the mean value for the rising edge delay time (or advance time), Δ, (as
illustrated in Figure 5.1.1-4) when the falling edge is viewed to be correct shall not exceed 1.0
ns.
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Complete PRN code
PRN code with late falling edge
PRN code with late rising edge
Δ Δ Δ
Δ Δ Δ Δ
Figure 5.1.1-4 Definition of delay time, Δ, for PRN code rising/falling edge
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5.1.1.7 PRN code phase relationships among signals
All QZS signals are generated from the same single clock with the operational frequency indicated in Section 5.1.1.2. The PRN code phase differences between QZS signals at the antenna phase center shall not exceed the values shown in Table 5.1.1-2.
Table 5.1.1-2 Differences in Pseudo Random Noise (PRN) code phases among QZS signals
L2 LEX L5
25 ns 35 ns 20 ns L1
15 ns 10 ns L2
20 ns LEX
The fluctuations in phase difference shall not exceed 2 ns for a value of 3σ. Within any 30 s period, QZS phase differences shall not exceed 0.01 ns ( 0.3 cm). These phase differences are included in navigation messages (TGD, ISC (Inter-Signal Correction), etc.) and transmitted to users. The accuracy is 4.5 ns (3-sigma) for TGD, and 3.0 ns (3-sigma) for ISC.
5.1.1.8 Minimum received power level
A ground-based isotropic antenna with a gain of 0 dBi for circularly polarized wave reception is provided and, when QZS signals are received from a Quasi Zenith Satellite (QZS) with an elevation angle of 10° or more, the reception power must not be lower than the value indicated in Table 5.1-1. In general, the reception power in each part of the service area is as shown in Section 3.1.3.6.
5.1.1.9 Polarization characteristics
All QZS signals are right-hand circularly polarized. The axial ratio (power ratio of the long axis to short axis) of the QZS circularly polarized waves, in the beam range of ± 10° from the boresight direction, shall not exceed 1.0 dB for the L1 signals and 2.0 dB for the L2, LEX and L5 signals. The axial ratio of the L1-SAIF signal is less than 1.0 dB.
5.1.1.10 Antenna Phase Center Characteristics
For all QZS signals with the exception of the L1-SAIF signal, the antenna phase center of the L-ANT is in the range of ± 1 cm in the beam range of ±10 deg from the direction of the L-ANT boresight. The L1-SAIF signal is transmitted from another antenna, LS-ANT. And the antenna phase center of the LS-ANT is in the range of +/- 1 cm from the direction of the boresight. Because the L1-SAIF signal is transmitted from the other antenna, the ephemeris data of L1-SAIF signal is not same as the ephemeris of the other signals, such as L1 C/A signal, L1C signal, L2C signal and L5 signal.
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5.1.1.11 PRN Code Numbers
5.1.1.11.1 Availability Enhancement Signals
QZSS uses the same type of PRN code as GPS. Detailed information are referenced in the sections starting with 5.2 and in Applicable Documents (1), (2) and (3). The PRN code numbers used by QZSS are 193-197. The initial QZS is assigned code number 193, and the second and succeeding QZS are assigned numbers in sequence starting with 194. PRN code numbers 198-202 are used for QZS maintenance/test purposes and must not be used by users.
5.1.1.11.2 Performance Enhancement Signals
(1) L1-SAIF signal A PRN code of the same type as the GPS L1C/A signal is used. For more information3 are referenced in the Applicable Documents (1). The PRN code numbers are 183-187. The initial QZS is assigned code number 183, and the second and succeeding QZS are assigned numbers in sequence starting with 184. PRN code numbers 188-192 are used for QZS maintenance/test purposes and must not be used by users.
(2) LEX Signal A small Kasami series is used. For more information, see Section 5.7. The numbers are 193-197. The initial QZS is assigned number 193, and the second and succeeding QZS are assigned numbers in sequence starting with 194. Numbers 198-202 are used for QZS maintenance/test purposes and must not be used by users.
3 The allowance of PRN Code is approved by GPSW through the process defined by “PSEUDO RANDOM (PRN) CODE ASSIGNMENT PROCESS”(GLOBAL POSTIONING SYSTEMS WING (GPSW), 1 February 2007). (The allowance of LIC signal will be approved officially after the IS-GPS-800 is established and the revision of above document is completed. The allowance of LIC for QZSS has been agreed at the GPS-QZSS TWG.)
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5.1.2 Navigational messages
5.1.2.1 Content of Navigation Messages
QZSS superimposes onto the PRN code data to aid identification of QZS position as well as other data described in the following subsections. As is typical of other GNSS systems, QZS transmits this information in the form of navigation messages. The content of the major QZSS navigation messages is shown below. For detailed information regarding the navigation messages broadcast on each QZSS signal, see the sections beginning with 5.2. 5.1.2.1.1 Ephemeris Data and SV Clock Parameters
QZSS provides users with Ephemeris data and SV clock parameters referenced to the QZS antenna phase center. These are available for positioning calculations on the part of users.
5.1.2.1.2 Almanac Data
QZSS provides Almanac data referenced to the QZS antenna phase center. These data are available for satellite selection calculations and Doppler calculations by users.
5.1.2.1.3 URA, Health Data
QZSS provides users with the URA and Health data (in case of L1C/A) shown in Figure 5.1.2-1.
Almanac Health
Ephemeris Health
RF Signal Strength Status
Navigation Message Status
Sum
mar
y+
Oth
er m
alfu
nctio
n
5 bits3 bits
5 bits1 bit
URA Index
4 bits
Accuracy
Subframe 4,5
Subframe 1
5 bits health3 bits health
1 bit health
Satellite Health
5 bits1 bit1 bit health
Summary+Other malfunction
Figure 5.1.2-1 QZS URA and Health Data on L1C/A signal
5.1.2.1.3.1 "Alert" Flag
The "Alert" flag is transmitted by all subframes of the L1C/A signal, by all message types of the L2C and L5 signals, and by bit 33 of subframe 2 of the L1C signal (the section named "L1C Signal Health" in Applicable Document (3)). When the ALERT flag is set to "1," this indicates that the SIS accuracy of the corresponding QZS signal is worse than 9.65 [m], or that an error of some kind has occurred on the QZS such that the specified accuracy cannot be guaranteed. Note that 9.65 [m] corresponds to the upper limit for the NMCT correction indicated in Section 5.2.2.2.5.2 (8). The operating concept for the ALERT flag is discussed in Section 3.1.2.1.3.
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QZSS constantly monitors the SIS error of the QZS signal and the status of the QZS and transmits the data to the user within the seconds, which is specified in Section 4.3.2.2 after an error has occurred. In such cases, use of the corresponding signal is not advised, however, users may do so at their own risk.
5.1.2.1.3.2 URA, URAoe, URAoc
URA index are transmitted by subframe 1 of the L1C/A signal, URAoe index are transmitted by message type 10 of the L2C and L5 signals, and subframe 2 of the L1C signal, and URAoc index are transmitted by message type 30, 31, 32, 33, 34, 35, 37, 46, 49, 51 and 53 of the L2C and L5 signals and subframe 2 of the L1C signal. These are related to the SIS error of the corresponding signal. Regardless of whether the "Alert" flag is set to "0" or "1", QZSS ensures that the current SIS error of the corresponding signal does not exceed the value expressed by URA, URAoe and URAoc. The probability that instantaneous URE (User Range Error) becomes greater than 5.73URA is less than 1 10-8 /h. The algorithm used to determine the value of URA, URAoe and URAoc from URA index, URAoe index and URAoc index is the same as that in Applicable Documents (1), (2) and (3). QZSS constantly monitors the SIS error of all QZS signals and generates the URA parameters based on the data received at Monitor Stations for the past 30 seconds. The URA parameters are transmitted for use as reference data. When the URA parameters indicate poor accuracy, use of the corresponding signal is not advised, however, users may do so at their own risk.
5.1.2.1.3.3 5-bit Health
The 5-bit health word is transmitted by the last 5 bits of the Ephemeris health [Section 5.2.2.2.3(4)] included in subframe 1 of the L1C/A signal, and the last 5 bits of the Almanac health [Section 5.2.2.2.5.2(2)(b)] and satellite health [Section 5.2.2.2.5.2(3)] included in subframes 4 and 5. The data included in the 5-bit health relate to the signal health of the satellite, such as L1 C/A signal, L2C signal, L5 signal, L1C signal and LEX signal. Each bit is set to "0" when the signal at the satellite is broadcasted correctly and available, and is set to ”1” when the health of each signal is bad. The definition of the bit allocation is shown in the Table 5.1.2-1. For GPS satellites, if the signal is not broadcasted or the status of the signal is unhealthy (judged by MCS), the 1 bit health of the signal is set to "1". In the case of the 1bit health="1", the signal of the satellite should be used at the user’s own risk.
Table 5.1.2-1 Details of Health (5-bit health) code for all QZSS signals Bit Allocation QZS Health GPS Health Notes
Bit 1 (MSB) Health of L1C/A signal Health of L1C/A signal
Bit 2 Health of L2C signal Health of L2C signal
Bit 3 Health of L5 signal Health of L5 signal
Bit 4 Health of L1C signal Health of L1C signal
Bit 5 (LSB) Health of LEX signal reserved Set “1” when GPS
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5.1.2.1.3.4 3-bit health and 1-bit health
The 3-bit health word is transmitted by the first 3 bits of the Almanac Health [5.2.2.2.5.2(2)(b)] included in subframe 4 and 5 of the L1C/A signal. The 1-bit health word is transmitted by the first bit of the Ephemeris Health [5.2.2.2.3(4)] included in subframe 1 of the L1C/A signal, by the first bit of the Satellite Health [5.2.2.2.5.2(3)] included in subframe 4 and 5, by "L1 Health", "L2 Health" and "L5 Health" in message type 10, 12, 31 and 37 in the L2C and L5 signals, and by "L1 Health", "L2 Health" and "L5 Health" on pages 3 and 4 in subframe 3 of the L1C signal. These Health bits indicate the status of the Navigation Message for the QZS signal transmitted by the associated satellite. The definition of the 3-bit Health word is the same as in Section 20.3.3.5.1.3 in Applicable Document (1). The 1-bit Health is set to "1" in the event that there is an error with any one or more of the following: the Navigation Message, power level, modulation, etc. QZSS constantly monitors the status of not only the QZS but also other satellite positioning systems including GPS. The MCS judges whether the system is in normal or error status and then generates these bits accordingly and provides the data to the user within the seconds, which is specified in Section 4.3.2.2. For all codes other than that corresponding to “All Signals OK”, users are cautioned to only use the associated signal at their own risk.
5.1.2.2 Timing of subframes, pages and data sets
5.1.2.2.1 IODE, IODC
The IODE in the same data set has the same 8 bits as the 8 LSBs of the 10-bit IODC. (In other words, if the last 8 bits of IODE and IODC are the same, these constitute the same data set.) In addition, unlike GPS’s IODC, 2bits (MSB) of IODC in QZSS signals are used as counter for SV clock parameter and count up once every 15 minutes. For transmissions of IODE and IODC for different data sets, the following rules apply:
(1) The transmitted IODC is different from the value transmitted from the satellite for the
previous seven days.
(2) The transmitted IODE is different from the value transmitted from the satellite for the
previous six hours.
(3) When updating only the SV Clock parameter without updating the Ephemeris data, only the
first two bits of the IODC are updated. In such cases, the epoch of the SV Clock parameter is
not updated. It is the same as the epoch of the Ephemeris data.
5.1.2.2.2 Relationship between epoch data and data set update
The epoch for Ephemeris data that possesses a new data set is assured to be different from that transmitted prior to updating.
5.1.2.2.3 Data set update
With the exception of the first data set after service is resumed following orbit maintenance and attitude maintenance (as described in Section 3.1.2.2.1.1 and 3.1.2.2.1.2, respectively), the data set is updated at the boundary of whole number hours. The initial data set may be updated to a new data set at any time, even during the effective period for that data set. The beginning of the transmission interval for each data set is the same: the beginning of the curve fit interval for the data set. The data set is valid for the duration of the curve fit interval.
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In the process of updating the shortest data set, the data sets in subframes 1, 2 and 3 in the L1C/A signal, in message type 10 and 11 in L2C and L5 signals, and in subframe 2 in the L1C signal are updated once per hour. The corresponding curve fit interval is 2 hours.
5.1.2.2.4 Data set update at the end-of-week crossover
At the end-of-week crossover, the L1C/A signal transmission starts again from subframe 1. In addition, the subframe 4 and 5 cycles that are dependent on the data set start again at the end-of-week crossover, regardless of what pages were transmitted prior to the end-of-week crossover. The L2C and L5 signals start again from message type 10 at the end-of-week crossover. The cycles for message types that are dependent on the data set start again at the end-of-week crossover, regardless of what message types were transmitted prior to the crossover. With the L1C signal, at the end of week crossover, the cycles for message types that are dependent on the data set start again at the end of week crossover, regardless of what message types were transmitted prior to the crossover.
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5.2 L1C/A signal
5.2.1 RF characteristics
5.2.1.1 Signal configuration
In accordance with Section 5.1.
5.2.1.2 Carrier wave properties
In accordance with Section 5.1.
5.2.1.3 Code properties
5.2.1.3.1 Code attributes
Same as in Sections 3.2.1.3 and 3.3.2.3 of Applicable Document (1). However, the PRN code is as described in Section 5.1.1.11.1 of this document.
5.2.1.3.2 Non-Standard Code (NSC)
In the event that a problem with the satellite or the ground-based system occurs, a non-standard code (NSC) is transmitted. This is done to protect users by ensuring that they do not receive or use erroneous navigation data.
5.2.2 Messages
5.2.2.1 Message configuration
Each word is made up of 30 bits. Ten words make up one subframe. Five subframes make up one loop. This message configuration is the same as in Applicable Document (1).
5.2.2.1.1 Preamble
The 8-bit preamble added to the beginning of the 10 words of the subframe is the same as in Section 20.3.3.1 of Applicable Document (1).
5.2.2.1.2 Parity algorithm
The 6-bit parity bits are added to the end of the 30-bit word is the same (32, 26) Hamming Code as specified in Section 20.3.5.1 of Applicable Document (1).
5.2.2.1.3 Parity Check algorithm
See section 20.3.5.2 of Applicable Document (1).
5.2.2.2 Message content
5.2.2.2.1 Telemetry word (1st word)
This word is used for QZSS maintenance/test purposes.
5.2.2.2.2 Handover word (HOW) (2nd word)
With the exception of the following, same as 20.3.3.2 in Applicable Document (1). For information on the use of the "Alert" flag in bit 18, see Section 3.1.2.1.3. For information on the content of the "Alert" flag, see Section 5.1.2.1.3. The Anti-Spoof flag (A-S), bit 19, is "0" indicating that the QZSS is in non-A-S mode.
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5.2.2.2.3 Subframe 1
Subframe 1 includes the clock data, etc. for the corresponding satellite. For more information regarding the general content of subframe 1, see Section 20.3.3.3.1 in Applicable Document (1). The parameter characteristics of Subframe 1 (number of bits, LSB scale factor, range, unit, data structure (page format etc.) etc.) are the same as in Section 20.3.3.3.2 in Applicable Document (1).
(1) Transmission Week Number Same as 20.3.3.3.1.1 in Applicable Document (1).
(2) L2 channel code Bits 11 and 12 (L2 channel code) in word 3 are fixed at "10."
(3) Satellite User Ranging Accuracy Index: URA Index Bits 13-16 in word 3 constitute the URA index. The algorithm signified by this URA index that is used to determine the specific user positioning accuracy for the satellite is the same as in Section 20.3.3.3.1.3 in Applicable Document (1). For more information about how to use the URA index, see Section 3.1.2.1.3. For more information about the content of URA, see Section 5.1.2.1.3.
(4) Health Data for the Satellite (Ephemeris Health) Bits 17-22 in word 3 constitute the health of the corresponding QZS. For more information on how to use the Ephemeris health, see Section 3.1.2.1.3. Health data (Almanac Health and Satellite Health) are also present in Subframe 4 & 5, but the refresh cycle for the Health data in Subframe 1 is more rapid, so the data are not identical. (a) Summary of Navigation Message status for signals transmitted by the corresponding
QZS (1-bit health) Bit 17 in word 3 shows a summary of the navigation message. The definition is in accordance with Section 20.3.3.3.1.4 in Applicable Document (1).
(b) Status of signals transmitted by the corresponding QZS (5-bit Health) Bits 18-22 in word 3 indicate the status of the signals transmitted by the corresponding QZS. The definition is in accordance with Table 5.1.2-1.
(5) Issue of Data, Clock (IODC) Bits 23 and 24 in word 3 indicate the 2 MSBs of the 10-bit IODC. Bits 1 - 8 in word 8 indicate the 8 bits beginning with LSB in the IODC. IODC shows issuance number of data set. Users can detect the update of data set by the time series behavior of IODC. IODC is changed each time the SV Clock parameters (af0, af1, af2 etc.) are updated. The shortest update period is every 900 seconds. For more information regarding IODC changes, etc., see Section 5.1.2.2.
(6) Data flag for L2P code As there is no L2P code, bit 1 in word 4 is fixed at "1."
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(7) Internal signal group delay error parameter
Bits 17-24 in word 7 indicate the internal signal group delay error parameter GDT for users who use only the L1C/A or only the L2C signal. For the definition and user algorithm, see Section 6.3.3 and 6.3.4. Bit string "10000000" indicates that the group delay value cannot be used.
(8) SV Clock parameters For information regarding the SV Clock parameters (toc, af2, af1, af0) needed for users to correct the SV clock offset, see Section 20.3.3.3.1.8 in Applicable Document (1). The user algorithm is described in Section 6.3.2.
5.2.2.2.4 Subframe 2 & 3
Subframe 2 and 3 contain the Ephemeris data, etc., for the corresponding satellite. For more information on the general content, see Section 20.3.3.4.1 in Applicable Document (1). The parameter characteristics of Subframe 2 and 3 (number of bits, LSB scale factor, range, unit, sub-commutation, etc.) are the same as in Section 20.3.3.4.2 in Applicable Document (1).
(1) AODO = NMCT (Navigation Message Correction Table) effective time
Bits 288 - 292 of subframe 2 constitute the effective time for the NMCT (navigation message correction table). The parameter characteristics of Subframe 2 and 3 (number of bits, LSB scale factor, range, unit, data structure (page format etc.), etc.) is the same as in Section 20.3.3.4.2 of Applicable Document (1). The certain part of the user algorithm is not same as in Section 20.3.3.4.4 of Applicable Document (1). When AODO is a binary value of “11111”, NMCT cannot be used. This is also the same as in Section 20.3.3.4.4 of Applicable Document (1). The NMCT is transmitted from different QZS at different timings. Among these NMCT, the most recent NMCT is the one with the largest tnmct value calculated using following equations..
AODOtt oenmct Note: nmctt must account for the beginning or end of week crossover in following equations.
800,604ttthen400,302ttif800,604ttthen400,302ttif
nmctnmctnmct
nmctnmctnmct
oet : Reference time Ephemeris (seconds into week) of the AODO broadcasting satellite [s] t : User receiver time (in GPST)
If calculated nmctt is larger than User receiver time t , NMCT is available, and otherwise, NMCT is not available. In addition, to respond the crossovers by ephemeris updates, if the difference between oet and t is less than 300 [s], ERD should not be used.
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validNOT,elseVALIDareERDs,else
validNOT,s300ttif
,0ttifetargt
oe
nmct
etargt
oet : Reference time ephemeris for the target satellite to correct
(2) Issue of Data, Ephemeris (IODE) Bits 61 - 68 of subframe 2 and bits 271 - 278 of subframe 3 constitute the IODE. The meaning of IODE is the same as in Section 20.3.4.4 of Applicable Document (1). IODE changes each time the Ephemeris data (a, e, i and the other 6 orbital elements and CIC, CIS and other correction parameters) are updated. The shortest update period is 1 hour. For more information on the use of IODE changes, etc., see Section 5.1.2.2.
(3) Ephemeris data The Ephemeris data defined in Section 20.3.3.4.1 of Applicable Document (1) are transmitted by subframe 2 and 3. The user algorithm described in Section 6.3.5.
(4) Fit interval flag: Effective time flag for Ephemeris data Bit 17 in word 10 of subframe 2 is the fit interval flag. When the curve fit interval is set to “0”, the Ephemeris data are effective for 2 hours. When the curve fit interval is “1”, the Ephemeris data are effective for more than 2 hours.
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5.2.2.2.5 Subframe 4 & 5
Subframes 4 and 5 include the Almanac data, Almanac Reference Week Number, Coordinated Universal Time (UTC) parameter, Ionosphere parameter, NMCT, etc. The parameter characteristics of subframes 4 and 5 (number of bits, LSB scale factor, range, unit, data structure (page format etc.) etc.) are the same as in Section 20.3.3.5.1 of Applicable Document (1). Unlike GPS legacy navigation message in Applicable Document (1), 25 pages for QZSS do not necessarily constitute one data set. The content of the transmitted data can be identified using the SV ID and the data ID. For instance, the data set can be extended to 30 pages or more to send several GNSS system parameters by using this flexible page concept. 5.2.2.2.5.1 Subframe 4 & 5 content identification
(1) Data identification The content of Subframes 4 and 5 can be distinguished by means of the data ID in bits 61 - 62 and the Space Vehicle (SV) ID in bits 63 - 68. The data ID identifies the type of satellite positioning system (for example, GPS, QZSS, etc.). The SV ID identifies the Space Vehicle Number of the satellite and other information (for example, whether the data constitute an ionospheric parameter, NMCT, etc.). The method used for identification is shown in Table 5.2.2-1.
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Table 5.2.2-1 Content identification using Data ID and Space Vehicle ID
SV ID Data ID = 00 (b) (GPS)Data ID=01(b)、10(b)
(Spare)Data ID=11(b) (QZSS)
00(d) Dummy satellite Dummy satellite01~32(d) GPS satellite Almanac QZS almanac33~48(d) Spare
49(d)
GPS satellite Almanac Reference Week Number, Almanac reference time and Satellite Health data of GPS satellite (PRN=1-24)
50(d)
GPS satellite Almanac Reference Week Number, Almanac reference time and Satellite Health data of GPS satellite (PRN=25-32)
51(d)
GPS satellite Almanac Reference Week Number, Almanac reference time and Satellite Health data of GPS satellite (PRN=1-24)
QZS Almanac Reference Week Number, Almanac reference time and Satellite Health data of QZS (PRN=193-197)
52(d)Navigation Message Correction Table (NMCT) for GPS satellite (PRN=1-30)
53(d)
Navigation Message Correction Table (NMCT) for QZS (PRN=193-197) and GPS satellite (PRN=31,32)
54(d)Navigation Message Correction Table (NMCT) for Spare satellite
55(d) Special message
56(d)GPS ionospheric parameters and relationship between UTC (USNO) and GPST
Ionospheric parameters especially for Japan and relationship between UTC (NICT) and GPST
57(d)58(d)59(d)60(d)61(d)62(d)
63(d)
A-S flag and Satellite Configuration of GPS (PRN=1-32) and Satellite Health data of GPS satellite (PRN=25-32)
Spare
Spare
Spare
Spare
Spare
(2) Data repeat transmission period Data repeat transmission period is depended upon Navigation pattern table (See Section 7.2.4.3)
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5.2.2.2.5.2 Content of subframes 4 & 5
(1) Dummy data When the SV ID is 0, the content comprises alternating values of 1 and 0.
(2) Almanac data and Almanac health When the SV ID is a value between 1 and 32, the content of that subframe comprises Almanac data and Almanac health. When the data ID is 11, the content is QZS Almanac data and Almanac health, and the eight bits of “data ID (2 bits) + SV ID (6 bits) “indicates the PRN number of the QZS. When the data ID is 00, the content is GPS Almanac data and Almanac health. The Almanac data and Almanac health for a GPS satellite that is visible (or has the potential to be visible) in at least the area shown in Section 4.1.1 are retransmitted. (a) Almanac data
Almanac data are entered in the sections of word 5 that do not include bits 17 – 24. The parameter characteristics (number of bits, LSB scale factor, unit etc.) of Almanac data is the same as in Section 20.3.3.5.1.2 of Applicable Document (1). The eccentricity (e) means offset from 0.06 and the reference value of the inclination is 0.25 [semi circles], which is different from the GPS definition. The Almanac data for the QZS are updated approximately once every 3.5 days. The velocity calculated by the Almanac data is accurate within 30 m/s The GPS Almanac data are GPS Almanac data gathered by the QZSS Monitor Stations. The user algorithm is described in Section 6.3.6.
(b) Almanac Health Almanac health is transmitted at the same time as Almanac data and is entered from bit 17-24 of word 5. This 8-bit Almanac health is divided into the first 3 bits and the last 5 bits. Definition of the first 3 bits are as shown in Section5.1.2.1.3.4. The last 5 bits are as shown in Section 5.1.2.1.3.3. The QZSS Master Control Station (MCS) constantly monitors the status of not only the QZS satellites but also other satellite positioning systems including GPS. The MCS makes judgments regarding normal or error status and generates Almanac health data, and provides these data to the user as reference data within the seconds, which is specified in Section 4.3.2.2.
(3) Satellite Health When the Data-ID=00 and the SV-ID=51, 63, and when the Data-ID=11 and the SV-ID=49, 50, 51, the content of that subframe indicates the satellite health. Satellite health comprises 6 bits for each satellite. The satellite health for multiple satellites is included in the subframe. This 6 bits satellite health is divided into the first 1 bit and last 5 bits. The definition of the first 1-bit health is shown in section 5.1.2.1.3.4, and the definition of the last 5-bits health is shown in section 5.1.2.1.3.3. The format and structure of the subframe is defined as same as the one defined in Applicable Document (1), and the sequence in the subframe is shown in Table 5.2.2-2.
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Table 5.2.2-2 Sequence of Satellite Health in the frame when Data-ID=11
Satellite HealthArea
Data ID=11SV ID=49
Data ID=11SV ID=50
Data ID=11SV ID=51
SV1 GPS PRN1 GPS PRN25 QZS PRN193SV2 GPS PRN2 GPS PRN26 QZS PRN194SV3 GPS PRN3 GPS PRN27 QZS PRN195SV4 GPS PRN4 GPS PRN28 QZS PRN196SV5 GPS PRN5 GPS PRN29 QZS PRN197SV6 GPS PRN6 GPS PRN30 SpareSV7 GPS PRN7 GPS PRN31 SpareSV8 GPS PRN8 GPS PRN32 SpareSV9 GPS PRN9 Spare SpareSV10 GPS PRN10 Spare SpareSV11 GPS PRN11 Spare SpareSV12 GPS PRN12 Spare SpareSV13 GPS PRN13 Spare SpareSV14 GPS PRN14 Spare SpareSV15 GPS PRN15 Spare SpareSV16 GPS PRN16 Spare SpareSV17 GPS PRN17 Spare SpareSV18 GPS PRN18 Spare SpareSV19 GPS PRN19 Spare SpareSV20 GPS PRN20 Spare SpareSV21 GPS PRN21 Spare SpareSV22 GPS PRN22 Spare SpareSV23 GPS PRN23 Spare SpareSV24 GPS PRN24 Spare Spare
When the SV-ID=51 and the Data-ID=11, it indicates the QZS satellite health. When the SV-ID=49 or 50 and the Data-ID=11, it indicates the health of GPS as judged by QZSS monitoring stations. The 24 MSBs of words 4 through 9 provide the satellite health status for 24 satellites to users. When the SV-ID=51 and the Data-ID=00, the contents is the same as the message in the case of SV-ID=49 and Data-ID=11. Therefore the combination of SV-ID=51 and Data-ID=00 won’t be used in future. When the SV-ID=63 and the Data-ID=00, the contents are A-S flag and Satellite flag for GPS PRN25-32). The structure of the message is same as that in Figure 20-1 (Sheet 9 of 11) of applicable document (1). Since the satellite health data for GPS (PRN 25-32) are also included in the message of SV-ID=51 and Data-ID=11, the combination of SV-ID=63 and Data-ID=00 won’t be used in future. Health data are also provided in subframe 1. Data for other satellites provided by means of subframes 1, 4 and 5 are uploaded at a different time, so it may differ from the data in subframes 4 and 5. The QZSS MCS constantly monitors the status of not only the QZS but other satellite positioning systems including GPS. The MCS judges whether the system is in normal or error status and then generates satellite health data and provides the data to the user within the seconds, which is specified in Section 4.3.2.2 for use as reference data.
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(4) Anti-Spoof flag and satellite configuration
When the SV ID is 63 and the data ID is 00, a 4-bit code (capacity for 32 items) is provided, indicating the GPS A-S status and configuration. This code is the same as in Section 20.3.3.5.1.4 of Applicable Document (1), and it constitutes a rebroadcast of the GPS AS flag and satellite configuration acquired by the QZSS MS. The combination of SV-ID=63 and Data-ID=00 won’t be used in future
(5) Almanac Reference Week Number When the SV-ID=51 & DATA-ID=00, or when SV-ID=49~51 & DATA-ID=11, bits 17 - 24 in word 3 indicate the Week Number (WNa) that serves as a reference for the Almanac Reference Time (toa) (see Section 20.3.3.5.1.2 and 20.3.3.5.2.2 of Applicable Document (1)). When the Data ID is 00 & SV-ID=51, or when Data-ID=11 & SV-ID=49 or 50, they indicate GPS Almanac Reference Week Number; when the Data ID is 11 & SV-ID is 51, it indicates a QZS Almanac Reference Week Number. WNa is made up of 8 bits and is a modulo-256 expression of the GPS Week Number (see Section 6.3.6) used as a reference. Word 3 indicates the toa referenced by WNa. When the Data-ID = 11 & SV-ID = 51, it indicates that the Almanac Reference Week Number is auxiliary data. In other words, if the current time, t, is near the weekend and the toa for the Almanac data is at the beginning of the week, the Almanac Reference Week is the following week. Moreover, if the current time is at the beginning of the week and the toa for the Almanac data is on the weekend, the Almanac Reference Week is the previous week. In other cases, the Almanac Reference Week is the current week. When the Data-ID = 00 and SV-ID = 51 or Data-ID=11 & SV-ID=49 or 50, the Almanac Reference Week Number is the same as in Section 20.3.3.5.1.5 of Applicable Document (1), and it constitutes a rebroadcast of the GPS Almanac Reference Week Number acquired by the QZSS MS. GPS almanac reference week number and almanac reference time broadcasted in the case of Data-ID=00 & SV-ID=51 are same as the message in the case of Data -ID=11 and Sat-ID=49 or 50. Therefore the combination of SV-ID=51 & Data-ID=00 won’t be used in future.
(6) Coordinated universal time parameter When the SV ID is 56, the 24 MSBs of words 6 - 9 and the 8 MSBs of word 10 contain the parameters for correcting UTC time to match GPS time. When the data ID is 00, it indicates a GPS rebroadcast, (the parameters to calculate the time offset between UTC (USNO) and GPS time). When the data ID is 11, it signifies the parameters to calculate the time offset between UTC (NICT) (with QZSS as the standard) and GPS time. The number of bits, scale factor, range and units are the same as in Table 20-IX of Applicable Document (1). The user algorithm is as noted in Section 6.3.7. The accuracy of the Coordinated Universal Time (UTC) parameter when the data ID is 00 or 11 is 90 [ns].
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(7) Ionospheric parameter
When the SV ID is 56, bits 9 - 24 in word 3 and the 24 MSBs of words 4 and 5 indicate the ionospheric parameters for use in the ionospheric model employed by users of only the L1C/A signal, LIC signal, L2C signal or L5 signal to calculate the ionospheric delay. When the data ID is 00, it indicates a GPS rebroadcast and the parameter is applicable worldwide. When the data ID is 11, it indicates that the ionospheric parameters have been generated by QZSS, and that the parameters have been specialized and are applicable within the area shown in Figure 4.1.5-1. These parameters usually, except ionospheric disturbance, use data for the past 24 hours (maximum) and are updated at least once each day. The number of bits, scale factor, range and units are the same as in Section 20.3.3.2.5 and Table 20-X of Applicable Document (1). For the user algorithm for users of only one signal, first the internal signal group delay error is corrected in accordance with Section 6.3.4, and then the ionospheric correction is performed in accordance with Section 6.3.8.
(8) Navigation Message Correction Table (NMCT) When the SV-ID=52~54 & DATA-ID=11, this indicates a Navigation Message Correction Table (NMCT). When the SV ID is 52, it indicates ERD values for GPS (PRN1 – PRN30). When the SV ID is 53, it indicates ERD values for QZSS (PRN193 - PRN197) and GPS (PRN31 & 32). When the SV ID is 54, it reserved for spares. The format and structure of the subframe is defined as same as the one defined in Applicable Document (1), and the sequence in the subframe is shown in Table 5.2.2-3.
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Table 5.2.2-3 Sequence of NMCT in the frame when Data-ID=11
ERD AreaData ID=11SV ID=52
Data ID=11SV ID=53
Data ID=11SV ID=54
ERD1 GPS PRN1 QZS PRN193 SpareERD2 GPS PRN2 QZS PRN194 SpareERD3 GPS PRN3 QZS PRN195 SpareERD4 GPS PRN4 QZS PRN196 SpareERD5 GPS PRN5 QZS PRN197 SpareERD6 GPS PRN6 GPS PRN31 SpareERD7 GPS PRN7 GPS PRN32 SpareERD8 GPS PRN8 Spare SpareERD9 GPS PRN9 Spare SpareERD10 GPS PRN10 Spare SpareERD11 GPS PRN11 Spare SpareERD12 GPS PRN12 Spare SpareERD13 GPS PRN13 Spare SpareERD14 GPS PRN14 Spare SpareERD15 GPS PRN15 Spare SpareERD16 GPS PRN16 Spare SpareERD17 GPS PRN17 Spare SpareERD18 GPS PRN18 Spare SpareERD19 GPS PRN19 Spare SpareERD20 GPS PRN20 Spare SpareERD21 GPS PRN21 Spare SpareERD22 GPS PRN22 Spare SpareERD23 GPS PRN23 Spare SpareERD24 GPS PRN24 Spare SpareERD25 GPS PRN25 Spare SpareERD26 GPS PRN26 Spare SpareERD27 GPS PRN27 Spare SpareERD28 GPS PRN28 Spare SpareERD29 GPS PRN29 Spare SpareERD30 GPS PRN30 Spare Spare
The NMCT begins with a 2-bit term indicating availability (AI), followed by a 6-bit ERD value consisting of up to 30 items. (a) AI (Availability Indication)
The AI is made up of bits 9 and 10 of Word 3. 00: Correction table is decoded and can be used 01: Spare 10: Correction table cannot be used 11: Spare
(b) ERD (Estimated Range Deviation) With regard to the NMCT ERD value, the MSB is the sign bit, while the LSB indicates 0.3 m, and the data range is ±9.3 m. A binary value of “100000” indicates that the ERD value does not exist. A binary value of “011111” indicates that the ERD value exceeds the upper limit. The user algorithm is as noted in Section 6.3.9.1.
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5.3 L1C Signal
5.3.1 RF Characteristics
5.3.1.1 Signal Configuration
Figure 5.3.1-1 shows the configuration of the L1C signal. The L1C signal is modulated onto the L1 RF carrier (in a similar way, but separately from, the L1 C/A and L1-SAIF QZSS signals) as specified in Section 5.1. This section specifies how the bit streams are generated for the two L1C signals: the L1C data signal (L1CD) and the L1C pilot (data-less) signal (L1CP). The L1CD bit stream is generated by the modulo-2 addition (XOR) of the L1C navigation message and the L1CD PRN ranging code. The L1CP bit stream is generated by the modulo-2 addition (XOR) of the L1C overlay code and the L1CP PRN ranging code. Each unique L1C PRN ranging code is at a chipping rate of 1.023 Mcps with a chip length of 10230 bits and a duration of 10 milliseconds. The L1CP overlay code is at a chipping rate of 100 bps with a chip length of 1800 bits and a duration of 18 seconds. The L1C navigation message is divided into three subframes (Time of Interval (TOI), Clock & Ephemeris (C&E) and Variable Data (Var)) that are Bose, Chaudhuri, and Hocquenghem (BCH) and 24-bit Cyclic Redundancy Check (CRC24) encoded. Subframes C&E and Var are further Low Density Parity Check (LDPC) encoded and subjected to interleaving. Then these subframes are integrated with the TOI subframe that has been BCH encoded.
Inner FEC½ Coder
(LDPC)Inter-
leaver
2nd PRN
as Overlay Code
100cps
1800chipL
1st PRN
as Ranging Code
1.023Mcps
10230chipL
Outer FECCoder(CRC 24) CNAV2
(100sps)
L1CP
L1CD
TOI(9bits)
C&E(576bits)
Var(250bits)
Outer FECCoder(CRC 24)
Outer FECCoder
(BCH 952)
Inner FEC½ Coder
(LDPC)
600bits
274bits
1200bits{s;p1;p2}
548bits{s;p1;p2}
1748bits
52bits 1800bits/18sec
L1CP(t)
L1CD(t)
L1CO(t)
Figure 5.3.1-1 L1C Signal Structure
5.3.1.2 Carrier Wave Properties
In accordance with Section 5.1.
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5.3.1.3 Code Properties
5.3.1.3.1 Overview of Code
As noted in Sections 5.3.1.1, there are two types of PRN code used for the L1C signals: unique PRN ranging codes for L1CD and L1CP, and an overlay code for L1CP. The methods used to generate both types of code are the same as the methods specified in Applicable Document (3). Specifically, the method noted in Section 3.2.2.1.1 of Applicable Document (3) is used to generate the PRN ranging codes. With regard to the specific L1C PRN numbers for the L1CD and L1CP signals to be broadcast by each QZS from among those numbers listed in Section 6.3.1.1 of Applicable Document(3), the numbers specified in Section 5.1.1.11.1 of this IS-QZSS document are to be used. Similarly, the method noted in Section 3.2.2.1.2 of Applicable Document (3) is used to generate the overlay codes. With regard to the specific PRN numbers for the overlay code of the L1CP signal to be broadcast by each QZS from among the numbers listed in Section 6.3.1.2 of Applicable Document (3), the numbers specified in Section 5.1.1.11.1 of this IS-QZSS document are to be used. For this reason, an S2 polynomial expression is needed for Fig. 3.2-2 in Section 3.2.2.1.2 of Applicable Document (3).
5.3.1.3.2 Non-Standard Code
In the event that a problem with the QZSS occurs, a non-standard code (NSC) is transmitted. This is done to protect the user by ensuring that users do not use erroneous signals.
5.3.2 Messages
5.3.2.1 Message Configuration
As noted in Section 5.3.1.1 in this manual, navigation messages are divided into three subframes: TOI, C&E, and Var. This message configuration is the same as specified in Section 3.2.3.1 of Applicable Document (3).
5.3.2.2 Encoding
As noted in Section 5.3.1.1 above, navigation messages are divided into three subframes: TOI, C&E and Var. Each of these subframes is BCH and CRC24 encoded. Furthermore, C&E and Var are further subjected to LDPC encoding. The encoding process used for these subframes is the same as specified in Sections 3.2.3.2 – 3.2.3.4 of Applicable Document (3).
5.3.2.3 Interleaving
As noted in the previous section, the C&E and Var subframes that are subjected to LDPC encoding are also interleaved and then integrated with the TOI subframe that has been BCH encoded. The interleaving process is the same as in Section 3.2.3.5 of Applicable Document (3).
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5.3.2.4 Message Content
With the exception of the list in Section 8.1.3, the content of the L1C message for QZSS is the same as that for GPS as specified in Section 3.5 of Applicable Document (3). 5.3.2.4.1 TOI (Subframe 1)
Prior to encoding, the TOI subframe is made up of 9 bits. TOI is incremented by 1 at each message period (= 18 seconds). TOI reverts to 0 every two hours. The valid range is 0-399. The initial TOI value for a two-hour period is 1. The final TOI value for a two-hour period is 0. These values are the same as the values specified in Sections 3.5.1 and 3.5.2 of Applicable Document (3).
5.3.2.4.2 C&E (Subframe 2)
Prior to encoding, C&E (subframe 2) is composed of 576 bits. The C&E data is used to calculate the orbital position and time of the QZS. This subframe includes the Ephemeris data, etc. for the satellite, such as the data shown in Table 5.3.2-1. For an overview, see Section 3.5.3 of Applicable Document (3). In all other respect except as specified in Section 3.1.2.1.2 and (10) in this section “Integrity Assurance”, this subframe is the same as specified in Section 3.5.3 of Applicable Document (3).
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Table 5.3.2-1 Definition of Ephemeris parameters and SV clock parameters for Navigational Message DL1C
Parameter Definition Difference from GPS definition
WNn GPS Week Number
ITOW
Interval time of week (ITOW) count defined as being equal to the number of two-hour epoch that has occurred since the transition from the previous week.
top Data predict time of week (seconds into week)
L1C Health L1C signal health
URAoe index Ephemeris accuracy Index.
toe Ephemeris epoch (seconds into week)
A Difference from Semi-Major Axis at toe In the case of QZS, indicates difference with 42,164,200 [m]
In the case of GPS, indicates difference with 26,559,710 [m]
A Change rate in Semi-Major Axis
n0 Difference from mean motion calculation at toe
0n Change rate in mean motion of calculation
M0-n Mean anomaly at toe
en Eccentricity QZSS does not limit the numerical range (In GSS, Maximum value = 0.03).
ωn Argument of perigee
Ω0-n Longitude of ascending node at the beginning of the week
Rate of right ascension of ascending node (RAAN) difference from reference value*1
i0-n Orbit inclination at toe
io-n-DOT Change rate in Orbit inclination
Cis-n Amplitude of the sine harmonic correction term to the angle of inclination
Cic-n Amplitude of the cosine harmonic correction term to the angle of inclination
Crs-n Amplitude of the sine correction term to the orbit radius
Crc-n Amplitude of the cosine correction term to the orbit radius
Cus-n Amplitude of the sine harmonic correction term to the argument of latitude
Cuc-n Amplitude of the cosine harmonic correction term to the argument of latitude
URAoc index SV clock accuracy index
URAoc1 index SV clock accuracy change index
URAoc2 index SV clock accuracy change rate index
af2-n SV clock drift rate correction term
af1-n SV clock drift correction term
af0-n SV clock bias correction term
TGD LCQZSS*2 and L1C/A group delay LCGPS
*3 and L1P(Y) group delay for GPS
ISCL1CP L1C/A-L1CP group delay L1P(Y) – L1CP for GPS
ISCL1CD L1C/A-L1CD group delay L1P(Y) – L1CD for GPS
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*1 Relative to ]condcircles/se-semi[106.2 9REF (same value with GPS)
*2 LCQZSS: LCQZSS is the ionospheric error free linear combination of the L1C/A and L2C signals for QZSS
*3 LCGPS: LCGPS is the ionospheric error free linear combination of the L1P(Y) and L2P(Y) signals for GPS
(1) Transmission Week No. Bits 1-13 of subframe 2 constitute a binary expression for the modulo-8192 representation of the current GPS Week Number. This is the same as in Section 3.5.3.1 of Applicable Document (3).
(2) ITOW (Interval Time Of Week) Bits 14-21 of subframe 2 constitute a number that is incremented by 1 every two hours starting from the beginning of the GPS week. The valid range is 0-83. The ITOW value for the two-hour period just prior to the week changeover is 83. The ITOW value for the first two-hour period of the week is 0. This is the same as in Section 3.5.3.2 of Applicable Document (3). The calculated “time of week” using TOI defined in Section 5.3.2.4.1 and ITOW is not always same as actual GPS time. This inconsistency occurs every two hours.
End/Start of week (GPS time)
2-hour epoch
TOI=1ITOW=0WN=2
TOI=0ITOW=83
WN=1
TOI=0ITOW=0WN=2
TOI=1ITOW=1WN=2
18 seconds
time
TOI=399ITOW=83
WN=1
2-hour epoch
1week,
604782s
1week,
597600s
2week,
18s
2week,
0s
2week,
7218s
1week,
604764s
2week,
0s
2week,
7182s
2week,
7200s
1week,
604782sActual GPS Time
Corresponding time to the message
2week,
7218s
same NOT same !
The corresponding time to the message dose not increase continuously .
NOT same !
Figure 5.3.2-1 Relationship between TOI, ITOW & time of week
(3) top (time at which Ephemeris data estimate is made)
Bits 22-32 of subframe 2 represents the time at which the Ephemeris data estimate is made (top). This is the same as in Section 3.5.3.3 of Applicable Document (3).
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(4) Signal Health (L1)
The single bit 33 of subframe 2 indicates the health of the L1C signal transmitted by the satellite. Signal health is expressed as follows. 0 No problems with signal 1 Problem with signal exists or signal cannot be used As an operation specific to the QZSS, this bit expresses the result of a comparison with the present status of the satellite as determined through monitoring. For more information, see Section 5.1.2.1.3. Additional SV health data are present on pages 3 and 4 of subframe 3 as well. The data in message type 10 are uploaded at a different time, so these data may differ from the data for the satellites transmitting other messages and other satellite data. In all other respects, this is the same as in Section 3.5.3.4 of Applicable Document (3).
(5) Ephemeris Data Accuracy Indicator (URAoe Index) Bits 34-38 of subframe 2 indicate the SIS accuracy indicator of the Ephemeris data. For more information, see Section 5.1.2.1.3.2. In all other respects, this is the same as in Section 3.5.3.5 of Applicable Document (3).
(6) Ephemeris Data The Ephemeris data for the corresponding satellite shown in Table 5.3.2-1 are transmitted in Subframe 2. The algorithm used to determine the orbital position of the satellite is in accordance with Section 6.3.5. With the exception of the QZSS-unique semi major axis parameter (specified in (a) below), the ephemeris data characteristics (number of bits, LSB scale factor, data range and units) are the same as in Table 3.5-1 of Applicable Document (3). The data structure (data sequence etc.) is the same as in Fig. 3.5-1 of Applicable Document (3). (a) Semi Major Axis Difference A A is the difference between the QZS semi major axis at toe A (toe) and 42,164,200 [m]: A (toe) = A (toe)-42,164,200 [m]
(7) Clock Parameters The SV clock parameters for the satellite, shown in Table 5.3.2-1, are transmitted. The user algorithm is the same as in Section 20.3.3.3.3.1 of Applicable Document (1). However, some of the parameter definitions are different. For more information, see Section 6.3.2. The epoch toe in the ephemeris data contained in bit 39-49 of subframe 2 is used as the epoch for the clock parameters. This is the same as in Section 3.5.3.7 of Applicable Document (3).
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(8) URAoc Index (accuracy indicator for SV clock parameters)
Bits 460-470 of subframe 2 contain the parameters needed to determine URAoc, which indicates the SIS accuracy of the SV clock parameters. For more information, see Section 5.1.2.1.3.2. With regard to the epoch for the accuracy indicator of the SV clock parameters, bits 22-32 of subframe 2 use the time top estimated by the Ephemeris data. This is the same as in Section 3.5.3.8 of Applicable Document (3). The algorithm used to determine the specific user range accuracy (URAoc) expressed by URAoc index is the same as in Section 3.5.3.8 of Applicable Document (3). For more information about the method of use and the content of URAoc, see Sections 3.1.2.1.3 and 5.1.2.1.3, respectively. Note: Refer to the above applicable document (3), URAoc is calculated in quadratic
equation of the time. The coefficient of the linear term and that of quadratic term would become larger than 0 by definition. The value of the linear term would become larger than 1.7578 m after 3600 seconds from the top because top is updated every 3600 seconds for QZSS.
(9) Calculation of Group Delay Error
Bits 527-565 of subframe 2 constitute the parameters TGD, ISCL1CP and ISCL1CD used to calculate the group delay error for users of only the L1C signal (i.e., single-frequency users). The number of bits, scale factor, range and units are shown in Table 3.5-1 of Applicable Document (3). Bit string "1000000000000" indicates that the group delay value cannot be used. Related algorithms are shown in Sections 6.3.3 and 6.3.4.
(10) Integrity Assurance One bit of bits 566 of subframe 2 of GPS is “Integrity Status Flag” (Refer to Applicable Document (3) Section 3.5.3.10). But QZS-1 does not adopt this Flag. Adding this one bit ISF to current QZSS L1C message after ”Phase Two” is under study.
5.3.2.4.3 Var (Subframe 3)
Var (subframe 3) comprises 250 bits prior to encoding. This subframe is used to transmit other data using multiple pages. Subframe 3 begins with 8 bits (193-197) that indicate the QZS satellite number from which the signal is transmitted, followed by a 6-bit page number. This is the same as in Section 3.5.4 of Applicable Document (3). 5.3.2.4.3.1 PRN No.
Bits 1-8 of subframe 3 constitute an 8-bit PRN number representing the PRN number for the QZS transmitting that message. This is the same as in Section 3.5.4 of Applicable Document (3).
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5.3.2.4.3.2 Page No.
Bits 9-14 of subframe 3 constitute a 6-bit page number signifying the information contained in that frame. The relationship between the individual page numbers and the corresponding information is shown in Table 5.3.2-2. Details are shown in Section 5.3.2.4.3.3. Table 5.3.2-2 also shows the maximum intervals at which each individual parameter is transmitted. Multiple QZS satellites may use completely different timings to transmit the data identified by page numbers. As a result, when the signals from multiple QZS satellites are received, all data sets can be collected at periods that are shorter than the data set transmission period for a single QZS satellite. As noted in Section 3.5.5 of Applicable Document (3), each page is transmitted using an arbitrary timing, so users should not expect a set pattern.
Table 5.3.2-2 Definition of page number and transmit periods for Navigational Message DL1C
Page Message data Maximum Interval Notes 1 Ionospheric parameter, UTC parameter 288 seconds 2 GGTO (GPS–QZSS Time Offset), EOP 288 seconds 3 Reduced Almanac of QZSS 20 minutes 4 Midi Almanac of QZSS 120 minutes 5 Differential correction data (DC)
[Ephemeris correction data, SV clock correction data] 30 minutes (*)
6 Text As needed 7 Spare - 17 Ionospheric parameter, UTC parameter (GPS Rebroadcasting) * 18 GGTO (GPS–Galileo Time Offset) (GPS Rebroadcasting) * 19 Reduced Almanac of GPS (GPS Rebroadcasting) * 20 Midi Almanac of GPS (GPS Rebroadcasting) *
* We will not define the maximum transmit period for GPS rebroadcasting parameters and GPS DC data.
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5.3.2.4.3.3 Content of Individual Pages
(1) Page No. 1 (17): UTC parameters/Ionospheric parameters Page 1 (17) includes the UTC parameters and ionospheric parameters such as shown in Table 5.3.2-3. For an overview, see Section 3.5.4.1 of Applicable Document (3).
Table 5.3.2-3 Definition of UTC parameters and Ionospheric parameters for Navigational Message DL1C Parameter Definition Difference from GPS definition
UTC
par
amet
ers
nA 0 Bias coefficient of GPST time scale relative to UTC time scale
When page No. is 1: Parameters indicate UTC(NICT) When page No. is 17 (rebroadcast of GPS message): Parameters indicates UTC(USNO)
nA 1 Drift coefficient of GPST time scale relative to UTC time scale
nA 2 Drift rate coefficient of GPST time scale relative to UTC time scale
LSt Current or past leap second count
tt0 Seconds into week for UTC and GPST bias calculation
tWN0 GPS Week Number for UTC and GPST bias calculation
LSFWN GPS Week Number at the end of which the leap second becomes effective.
DN Day number at the end of which the leap second becomes effective (First day number = 1).
LSFt Current or future leap second count
Iono
sphe
ric p
aram
eter
s
α0 Ionospheric parameter α0 for Klobuchar model
When page No. is 1: Parameters are optimized for Japan & environs When page No. is 17 (rebroadcast of GPS message): Parameters can be applied on global area
α1 Ionospheric parameter α1 for Klobuchar model
α2 Ionospheric parameter α2 for Klobuchar model
α3 Ionospheric parameter α3 for Klobuchar model
β0 Ionospheric parameter β0 for Klobuchar model
β1 Ionospheric parameter β1 for Klobuchar model
β2 Ionospheric parameter β2 for Klobuchar model
β3 Ionospheric parameter β3 for Klobuchar model
(Gro
up
Del
ay
Para
met
er)
- -
For GPS, Group Delay Parameters (ISC_L1CA, ISC_L2C, ISC_L5I5 and ISC_L5Q5) were added in Figure 3.5-2 of Applicable Document (3). While the message for QZS-1 did not adopt these parameters.
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(a) UTC Parameters
The UTC parameters are the parameters needed to relate GPS time to UTC (NICT). The number of bits, scale factor, range, units, LSB, user algorithm, etc. are all the same as Section 3.5.4.1 in Applicable Document (3).
(b) Ionospheric Parameters The ionospheric parameters are the parameters used when users of only one signal (L1, L2 or L5) employ an ionospheric model to calculate the ionospheric delay. The user algorithm for single signals is in accordance with Sections 6.3.4 and 6.3.8. The ionospheric parameters, optimized for the area near Japan, are specialized and apply to the area shown in Figure 4.1.5-1. These parameters use the data for the past 24-hour period (maximum) and are updated at least once daily, except ionospheric maximum period. The number of bits, scale factor, range and units are the same as Section 3.5.4.1.2 in Applicable Document (3).
(c) Estimation of Group Delay Error For QZS-1, Bit 177 - 250 in page 1 of subframe 3 is defined as "Spare". On the other hand, for GPS, Group Delay Parameters (ISC_L1CA, ISC_L2C, ISC_L5I5 and ISC_L5Q5) were added at bit 171 - 228 in Page 1 of subframe 3 (Referred to Figure 3.5-2 in Applicable Document (3)). The message for QZS-1 did not adopt these parameters. Future supports for adoptions of the Group Delay Parameters in QZSS are under study.
(2) Page No. 2 (18): GPS/GNSS Time Offset (GGTO) Parameters and Earth Orientation
Parameters (EOP) Page 2 includes the GPS/GNSS Time Offset (GGTO) Parameters, parameters that are used to adjust GPS time to match other GNSS system times, as shown in Table 5.3.2-4, and the Earth Orientation Parameters (EOP) that indicate the relationship between the earth's rotational axis and the Japan satellite navigation Geodetic System (JGS). With regard to the content of these parameters, see Section 3.5.4.2 in Applicable Document (3). The bit definition, number of bits, scale factor (LSB), range and units are all the same as Table 3.5-4 and 3.5-5 in Applicable Document (3). At a minimum, the valid period for GPS GNSS Time Offset (GGTO) is at least 24 hours. Page 18 is rebroadcast of GPS message.
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Table 5.3.2-4 Definition of GPS GNSS Time Offset (GGTO) and EOP parameters for Navigational Message DL1C
Parameter Definition Difference from GPS definition G
NSS
tim
e of
fset
GG
TO
GGTOA0 Bias coefficient of GPST time scale relative
to other GNSS time scale
GGTOA1 Drift coefficient of GPST time scale relative
to other GNSS time scale
GGTOA2 Drift rate coefficient of GPST time scale
relative to other GNSS time scale
GGTOt Seconds into GGTO reference week
GGTOWN GGTO Reference Week Number
GNSS ID See (a) in this section
Earth
orie
ntat
ion
para
met
ers E
OP
EOPt Seconds into EOP reference week
XPM X-Axis polar motion value at EOPt
XPMdtd X-Axis polar motion drift at EOPt
YPM Y-axis polar motion value at EOPt
YPMdtd Y-axis polar motion drift at EOPt
1UT UT1-UTC difference at EOPt
1UTdtd Rate of UT1-UTC difference at EOPt
(a) GNSS-ID
Bits 15-17 define the other GNSS that apply the GPS GNSS Time Offset (GGTO) parameters. The three-bit definitions are as follows: 000 Data cannot be used 001 Galileo 010 GLONASS 011 QZSS 100-111 Spare
(b) GPS/GNSS Time Offset (GGTO) The algorithms used to derive GPS GNSS Time Offset (GGTO) are the same as in Applicable Document (3). However, the SV clock parameter for the QZS already uses GPST as the standard, so the time offset between the GPS and QZSS (GQTO) is zero.
(c) Earth Orientation Parameter (EOP) The definition, number of bits, scale factor, range, units, LSB, user algorithm etc, are all the same as Section 3.5.4.2.2 in Applicable Document (3). When page number is 18, i.e. the page for rebroadcasting GGTO in GPS CNAV message, since QZSS does not broadcast EOP obtained from GPS CNAV message, the information obtained from bits 83 to 220 cannot be used.
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(3) Page No. 3 (19): Reduced Almanac
Page 3 includes the Reduced Almanac, as shown in Table 5.3.2-5. For an overview, see Section 3.5.4.3.5 in Applicable Document (3). The bit definition, number of bits, scale factor (LSB), range and units are all the same as Figure 3.5-9 and Table 3.5-6 in Applicable Document (3). When the PRN number is 63, the data packet includes dummy data without any effective information. The 22 bits are alternating ones and zeros, and the last 3 bits, which indicates the health, are all “1”s. The user algorithm is in accordance with Section 6.3.6. The Reduced Almanac is transmitted from a single satellite in a shorter period of time than the Midi Almanac. The Reduced Almanac data for the QZS are updated approximately once every 3.5 days. The velocity calculated by the Reduced Almanac data is accurate within 350 m/s. Page 19 is rebroadcast of GPS message.
Table 5.3.2-5 Definition of Reduced Almanac parameters for Navigational Message DL1C
Parameter Definition Difference from GPS definition
WNa-n GPS Week Number at the time of Reduced Almanac generation
toa Reduced Almanac epoch (seconds into week)
Red
uced
Alm
anac
×6 sa
telli
tes
PRN No. PRN number (range 0 - 255) for satellite for which Reduced Almanac will be applied. 1-32 if target is GPS; 193-197 if target is QZSS
δA Offset from the nominal QZS Semi-Major Axis of 42,164,200 [m]
In the case of GPS, indicates the offset from 26,559,710 [m]
Ω0 Longitude of ascending node at the beginning of the week
Φ0 Argument of latitude ( = M0 + ω)
(e) Implicit eccentricity (0.075 in the case of QZS) (Precondition for above parameter)
0 in the case of GPS
(δi)
Fixed at -0.0111 [semi-circles], the offset from reference QZS orbit inclination of 0.25 [semi-circles] (precondition for above parameter)
In the case of GPS, fixed at 0.0056 [semi-circles], the offset from 0.3 [semi-circles]
L1/L2/L5 Health L1,L2 and L5 signal health
( ) Implicit Argument of Perigee (270[deg] in QZS-1) (Precondition for above parameters) 0[deg] in case of GPS
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(a) Reduced Almanac Epoch (Week Number)
Bits 15-27 of subframe 3 indicate the Week Number (WNa-n) corresponding to the Reduced Almanac epoch (toa). WNa-n is made up of 13 bits and is expressed by the modulo-8192 value for the GPS Week Number (see Section 6.3.6) that serves as a reference for toa. This is the same as Section 3.5.4.3.1 in Applicable Document (3).
(b) Reduced Almanac Epoch (seconds into week) Bits 28-35 of a subframe 3 indicate the Reduced Almanac epoch (toa). This is the same as Section 3.5.4.3.1 in Applicable Document (3).
(c) 6 Reduced Almanac Packets Bits 36-233 of subframe 3 include six Reduced Almanac packets comprising 33 bits each. This is the same as Section 3.5.4.3.5 in Applicable Document (3).
(d) PRN Number. Bits 1-8 in each packet constitute the PRN number for the satellite indicated by that packet. The PRN number constitutes 8 bits and expresses a value from 0 to 255. The definition of these values is as follows. 1-32: GPS PRN No. 65-94: The value minus 64 indicates a Galileo PRN No. 129-160: The value minus 128 indicates GLONASS PRN No. 193-197: QZSS PRN No.
(e) Semi major axis Bits 9-16 in each packet provide the data (δA) relating to the semi major axis of the satellite indicated by the PRN number. For PRN No. 193-197 (QZSS): AmA ][200,164,42 For PRN No. 1-32 (GPS): AmA ][710,559,26
(f) Longitude of Ascending Node at the beginning of the week Bits 17-23 in each packet are the longitude of ascending node (Ω0) at the beginning of the week for the satellite indicated by the PRN number. This is the same as Figure 3.5-9 in Applicable Document (3).
(g) Argument of Latitude Bits 24-30 in each packet constitute the argument of latitude for the satellite indicated by the PRN number. This is the same as Figure 3.5-9 in Applicable Document (3).
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(h) Implicit Eccentricity
For the eccentricity, although this is not broadcasted as Reduced Almanac from QZS, users may use the following assumption. For PRN No. 193-197 (QZSS): 075.0e For other PRN numbers: 0.0e
(i) Implicit Inclination For the inclination, although this is not broadcasted as Reduced Almanac from QZS, users may use the following assumption. For PRN No. 193-197 (Q2SS): i = 43 [deg] For PRN No. 1-32 (GPS): i = 55 [deg]
(j) Implicit Time Change Rate for Right Ascension of Ascending Node (RAAN) For the time change rate for the right ascension of ascending node (RAAN), although this is not broadcasted as Reduced Almanac from QZS, users may use the following assumption. For PRN No. 193-197 (QZSS): ]condcircles/sesemi[107.8 10
For PRN No. 1-32 (GPS): ]condcircles/sesemi[106.2 10
(k) Signal Health (L1/L2/L5) The three one-bit health indicators (bits 31, 32 and 33) in each packet relate to the corresponding L1, L2 and L5 signals of the satellite with the associated PRN number. Their significance is in accordance with Section 5.1.2.1.3.
(l) Implicit Argument of Perigee For the argument of perigee, although this is not broadcasted as Reduced Almanac from QZS, users may use the following assumption. For PRN No. 193-197 (QZSS): [deg]270 For PRN No. 1-32 (GPS): [deg]0
(4) Page No. 4 (20): Midi Almanac Page 4 includes a Midi almanac like the one shown in Table 5.3.2-6. For an overview, see Section 3.5.4.3.6 in Applicable Document (3). The bit definition, number of bits, scale factor (LSB), range and units are all the same as in Figure 3.5-5 and Table 3.5-7 in Applicable Document (3). The user algorithm is in accordance with Section 6.3.6. The Midi Almanac data for the QZS are updated approximately once every 3.5 days. The velocity calculated by the Midi Almanac data is accurate with 30m/s Page 20 is rebroadcast of GPS message.
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Table 5.3.2-6 Definition of Midi Almanac parameters for Navigational Message DL1C
Parameter Definition Difference from GPS definition
WNa-n GPS Week Number at time of Midi Almanac
generation
toa Midi Almanac epoch (seconds into week)
PRN No.
PRN number (range 0 - 255) for satellite for
which Midi Almanac will be applied.
1-32 if GPS; 193-197 if QZSS
L1/L2/L5 Health L1,L2 and L5 signal health
Δe Eccentricity
(offset from reference eccentricity 0.06)
In the case of GPS, the offset from reference
eccentricity 0
Δi
Offset from reference inclination 0.25
[semi-circles]
(Offset from 0.25 [semi-circles]=45 [deg])
In the case of GPS, the reference inclination is
0.3 [semi-circles], which represents 54 [deg].
Change rate in Right ascension of ascending node
(RAAN)
A Square root of Semi-Major Axis
Ω0 Longitude of ascending node at the beginning of
the week
Ω Argument of perigee
M0 Mean anomaly
af0 SV Clock bias correction coefficient
af1 SV Clock drift correction coefficient
(a) Midi Almanac Epoch (Week Number) Bits 15-27 indicate the Week Number (WNa-n) corresponding to the Midi Almanac epoch (toa). WNa-n is made up of 13 bits and is expressed by the modulo-8192 for the GPS Week Number (see Section 6.3.6) that serves as a reference for toa. This is the same as Section 3.5.4.3.1 in Applicable Document (3).
(b) Midi Almanac Epoch (seconds into week) Bits 28-35 indicate the Midi Almanac epoch (toa). This is the same as Section 3.5.4.3.1 in Applicable Document (3).
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(c) PRN Number.
Bits 1-8 in each packet constitute the PRN number for the satellite. The PRN number constitutes 8 bits and expresses a value from 0 to 255. Within this range, the number categories are as follows. 1 - 32: GPS PRN No. 65 - 94: The value minus 64 indicates a Galileo PRN No. 129 - 160: The value minus 128 indicates GLONASS PRN No. 193 - 197: QZSS PRN No.
(d) Signal Health (L1/L2/L5) The three one-bit health indicators (bits 44, 45, 46) relate to the L1, L2 and L5 signals of the satellite corresponding to the PRN number. Their significance is in accordance with Section 5.1.2.1.3.
(e) Content of Midi Almanac Data Bits 47-165 include the Midi Almanac data for one satellite. With the exception of the eccentricity and inclination described below, this is the same as Figure 3.5-5 in Applicable Document (3).
(f) Eccentricity Bitts 47-57 provide data e relating to eccentricity e for the satellite indicated by the PRN number. For PRN no. 193-197 (QZSS): eea 06.0
For other PRN numbers: eea ea: Actual eccentricity value
e : Eccentricity value included in navigation message
(g) Inclination Bitts 58-68 provide data i relating to inclination for the satellite indicated by the PRN number. For PRN no. 193-197 (QZSS): ][25.0 circlesemiiia
For other PRN numbers: ][3.0 circlesemiiia ia: Actual inclination value
i : Inclination value included in navigation message
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(5) Page No. 5: Differential Correction Data (DC data)
Page 5 includes differential correction data (DC data) for one satellite, as shown in Table 5.3.2-7. This parameter provides the user with correction terms for the SV clock parameters and Ephemeris data transmitted by other satellites. DC data are packetized data comprising a 34-bit SV clock error (CDC) correction parameter and a 92-bit Ephemeris error (EDC) correction parameter. The CDC and EDC data form a pair; users must use CDC and EDC with the same top-D and tOD as a pair. For a DC Data Type indicator, "0" indicates that the correction applies to CNAV2 data. "1" indicates that the correction applies to the navigation message for the L1C/A signal. The content of the data packet is the same as Section 3.5.4.4 in Applicable Document (3) and is shown in Table 5.3.2-7. The bit definition, number of bits, scale factor, range and units for DC data are the same as Section 3.5.4.4 in Applicable Document (3). If the DC data is not effective, the value of the PRN Number is set to “11111111” as Section 3.5.4.4.1 in Applicable Document (3). In this case, DC data type indicator is set to “0”.
Table 5.3.2-7 Definition of DC data for Navigational Message DL1C
Parameter Definition Difference from GPS definition
top-D Prediction time of week for DC data (seconds in week)
tOD Reference time of week for DC data (seconds in week)
DC Data Type indicator 1:For DL1C/A message 0:For DL1C message
CD
C
PRN No. PRN No. (range 0 - 255) for satellite for which DC data will be applied. 1 – 32 if target is GPS; 193-197 if target is QZSS
0fa Bias correction term for SV clock
1fa Drift correction term SV clock
UDRA index User Differential Range Accuracy (UDRA)
index
EDC
PRN No. PRN No. (range 0 - 255) for satellite for which DC data will be applied. 1 – 32 if target is GPS; 193-197 if target is QZSS
α α correction term for Ephemeris parameter
β β correction term for Ephemeris parameter
γ γ correction term for Ephemeris parameter
i Correction term for orbit inclination
Ω Correction term for right ascension of ascending node (RAAN)
A Correction term for Semi-Major Axis
UD.
RA index UDRA rate index
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DC data include the following. The use of these data is in accordance with Section 3.1.2.1.3.4. (a) Time of DC data Estimation (top-D)
“top-D” indicates the time (seconds into week) at which DC data are estimated. This is the same as Section 3.5.4.4.2 in Applicable Document (3).
(b) DC Data Epoch (tOD) “tOD” indicates the epoch (seconds into week) of DC data. This is the same as Section 3.5.4.4.3 in Applicable Document (3).
(c) Identification of Satellite PRN The 8-bit PRN specifies the satellite to which DC data applies. A PRN of 1-32 indicates GPS. A PRN of 193-197 indicates QZSS. When all of the bit values are "1," it indicates that there are no DC data in the data block. In such cases, as Section 3.5.4.4.1 in Applicable Document (3), alternate bit values of "1" and "0" are entered for the remaining data.
(d) Use of CDC Data This is the same as Section 3.5.4.4.4 in Applicable Document (3). For more information, see Section 6.3.9.2.
(e) Use of EDC Data This is the same as Section 3.5.4.4.4 in Applicable Document (3). For more information, see Section 6.3.9.2.
(f) Accuracy of DC Data UDRAop-D and UDRA-DOT indicate the ranging accuracy after the DC data have been applied to the SV clock parameters and Ephemeris data. The bit definition, number of bits, etc., and user algorithms are the same as Section 3.5.4.4.4 and Table 3.5-10 in Applicable Document (3). The use of this value is in accordance with Section 3.1.2.1.3.5.
(6) Page No. 6: Text Message Page 6 includes 29 eight-bit ASCII characters. All bit definitions, number of bits, etc., are in accordance with Figure 3.5-7 in Applicable Document (3).
(7) Page No. 7: (Reserved) (Reserved): Same as Section 3.5.4.6 in Applicable Document (3).
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5.4 L1-SAIF signal
5.4.1 RF characteristics
5.4.1.1 Signal configuration
In accordance with Section 5.1.
5.4.1.2 Carrier wave properties
In accordance with Section 5.1.
5.4.1.3 Code properties
5.4.1.3.1 Code attributes
Same as in Sections 3.2.1.3 and 3.3.2.3 of Applicable Document (1). However, the PRN code is as described in Section 5.1.1.11.2 of this document.
5.4.2 Error Correction Code
The data transmission rate for the L1-SAIF message is 250 bps. However, the data bits are encoded by the Forward Error Correction (FEC) generator resulting in a 500 sps message for transmission. The FEC encoding factor is ½ and the constraint length is 7. Figure 5.4.2-1 shows the FEC generator used for encoding. G1 register tap is selected for the first 2 msec of a 4 msec message stream for 250 bits and G2 tap is done for latter 2 msec message.
Figure 5.4.2-1 FEC Generation Method
5.4.3 Message
The content of the SAIF message broadcast using the L1-SAIF signal is specified below. 5.4.3.1 Message Configuration
Each message in the L1-SAIF signal is made up of 250 bits and has the format shown in Figure 5.4.3-1. The data rate is 250 bps, so one message is transmitted every second. The 8-bit preamble begins from bit 1 of the 250-bit message. Next, the 6-bit message type identifier is inserted (bits 9-14). The 212-bit data domain begins from bit 15, and the 24-bit CRC parity begins from bit 227. The message transmission sequence is not specified; any message type may be transmitted during any one-second period.
DATA INPUT
(250 BPS)
+
+
+ + + +
+ +
SYMBOL CLOCK
G2 (133 OCTAL)
OUTPUT SYMBOLS
(500 SPS)
ALTERNATING G1/G2
G1 (171 OCTAL)
G1 is selected initially
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Figure 5.4.3-1 Message Block Format
5.4.3.1.1 Preamble
The preamble added to the beginning of each message consists of the following three patterns repeated in sequence:
Pattern A 01010011 Pattern B 10011010 Pattern C 11000110
The start of transmission of the first bit in the Pattern A preamble is synchronous with the epoch of the 6-second L1C/A signal navigation message subframe. The preamble of the next message to be transmitted after the message with the Pattern A preamble is Pattern B. After Pattern B comes Pattern C. After that, the sequence returns to Pattern A. FEC encoding is performed for preambles in the same manner as for the other bits in the message block. Accordingly, while the preamble indicates the beginning of the message block, it cannot be used for signal acquisition prior to FEC decoding or for bit synchronization.
212-BIT DATA FIELD
6-BIT MESSAGE TYPE IDENTIFIER (0-63)
8-BIT PREAMBLE OF 24 BITS TOTAL IN 3 CONTIGUOUS BLOCKS
24-BITSPARITY
250 BITS – 1 SECOND
DIRECTION OF DATA FLOW FROM SATELLITE;MOST SIGNIFCANT BIT(MSB) TRANSMITTED FIRST
212-BIT DATA FIELD
6-BIT MESSAGE TYPE IDENTIFIER (0-63)
8-BIT PREAMBLE OF 24 BITS TOTAL IN 3 CONTIGUOUS BLOCKS
24-BITSPARITY24-BITSPARITY
250 BITS – 1 SECOND
DIRECTION OF DATA FLOW FROM SATELLITE;MOST SIGNIFCANT BIT(MSB) TRANSMITTED FIRST
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5.4.3.1.2 Message Type
Each message has a 6-bit Message Type ID. Messages are identified by a Message Type ID ranging from 0 to 63. The content of the data field is defined as noted below according to the Message Type. Table 5.4.3-1 shows a list of message types.
Table 5.4.3-1 SAIF Message Types Message Type ID Message Name Remarks
0 Test mode
1 PRN mask
2~5 Fast Correction & UDRE
6 Integrity data
7 (Fast Correction Degradation Factor)
10 Degradation Parameter
18 IGP mask
24 Mixed Fast/Long-term Correction
25 Long-term Correction
26 Ionospheric Delay & GIVE
28 Clock-ephemeris Covariance
40 ~ 51 Reservation for applications demonstration L1-SAIF+ Unique Message
52 TGP mask
53 Tropospheric Delay Correction
54~55 (Atmospheric delay correction) TBD
56 Inter Signal Bias Correction data
57 (Reserved for orbital information) TBD
58 QZS ephemeris Provisional
59 QZS Almanac data TBD
60 (Regional information/maintenance schedule) TBD
62 (Reserved for Inertial test)
63 Null message
5.4.3.1.3 CRC Parity
A 24-bit CRC parity code is added to the end of the message. In the event of either a burst error or a random error causing a bit error rate of ≦ 0.5, the 24-bit CRC parity protects the message with an error miss rate ≦2-24
=5.96×10-8. The following generating polynomial is used for CRC parity: 13456710111417182324 XXXXXXXXXXXXXXg
User receivers must check the CRC parity of received messages. If there is a mismatch, the data in that message should not be used.
5.4.3.2 Use of Messages
The method of using SAIF messages is specified below.
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5.4.3.2.1 QZS Selection
When using SAIF messages, the SAIF message transmitted from a satellite that is currently in use should be used. Either of the following two methods may be used when switching satellites.
(1) Parallel processing method: Before the changeover, the SAIF message being transmitted by
the successor satellite is received and processed independently from the SAIF message being
received from the current satellite. The changeover is initiated when all of the data needed for
positioning have been successfully received from the successor satellite.
(2) Serial processing method: The user receiver’s positioning output must be temporarily halted
while changing satellites and all SAIF messages received from the former satellite must be
deleted. Following the changeover, the SAIF message transmitted by the successor satellite is
received and processed, and positioning output is resumed when all of the data needed for
positioning have been successfully received from the successor satellite.
The parallel processing method allows positioning output to be maintained continuously. However, at the time of changeover, both new and old SAIF messages must be processed in parallel. The serial method simplifies message processing, but positioning output cannot be continuous and must be stopped for several minutes. The serial method is similar to the processing performed following receiver power-on.
5.4.3.2.2 Minimum Elevation Angle
The elevation angle of any satellite being used for augmentation data (via the QZSS SAIF message) must be at least 5° above the horizon as viewed from the user position.
5.4.3.2.3 Selection of Positioning Satellites and Signals
Of the satellites for which QZSS provides augmentation data (via the SAIF message) and the satellites actually indicated by the PRN mask, the satellites used for positioning by the user receiver may be freely selected from among those that are above the specified 5° minimum elevation angle as viewed from the user position. Received QZS signals should be used in accordance with the following:
(1) The L1 frequency signals may be used as long as they are indicated by the PRN mask.
(2) Other frequencies can be used in place of the L1C/A signal for the same satellite after the
Inter Signal Bias correction data in message type 56 have been applied. However, the
ionospheric propagation delay must be corrected as needed in accordance with the frequency.
5.4.3.2.4 Numerical Expression
Each data included in the SAIF message are expressed by fixed-point number representation. The specified bit sequence is transmitted from MSB to LSB and decimal point is located righthand of LSB. The necessary data can be obtained by multiplied integer value by resolution specified for each item. The two’s complement is used for expression of both plus and minus data.
5.4.3.3 Message Content (SBAS Compatible Message)
5.4.3.3.1 Message Type 0 (Test Mode)
Message type 0 indicates that the L1-SAIF signal is in test mode. When a type 0 message has been received, the receiver should delete all SAIF messages received up to that point, and SAIF messages transmitted for the subsequent 60 seconds must also not be used.
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5.4.3.3.2 Message Type 1 (PRN Mask)
Message type 1 contains a PRN mask. A PRN mask constitutes flag data that indicate a satellite for which augmentation data will be provided. Of the satellites in PRN slots 1 - 210, PRN masks may be set for up to 51 satellites. Satellites for which PRN masks have been set are assigned PRN mask numbers in sequence starting with the lowest PRN slot number. The range of PRN mask numbers is 1 - 51. In message types 25, 28 and 56 the target satellite is specified directly by the PRN mask numbers 1 - 51. In message types 2 - 7, the correspondence between the correction data slot and the PRN mask number is established in advance. Following the 210-bit PRN mask, a 2-bit PRN mask issue number (IODP) is transmitted. This number is incremented each time the PRN mask is updated (note that, since the IODP is only 2-bits, after 3 comes 0). Other message types that reference the PRN mask number include IODP corresponding to the PRN masks that should be used by receivers, so receivers should constantly monitor the PRN masks matching the IODP and convert them to PRN slot numbers. For QZSS, PRN mask updating differs from that specified in the Minimum Operational Performance Standards (MOPS) (Applicable Document (4)) and is not necessarily conducted only when a new satellite is launched or when a satellite goes out of service. In order to ensure the efficient use of message bandwidth, the combination of satellites for augmentation will be updated as needed. Other message types that reference the PRN mask number always require effective PRN masks, so before the IODP for other messages is updated, a new PRN mask is transmitted by means of message type 1. When a new PRN mask is received, the receiver retains both old and new PRN masks for some time, and consideration must be given to ensuring the use of the appropriate PRN mask until the IODP for other message types is updated. When the IODP for a message type other than type 1 has been updated, the old PRN mask may be deleted. In other words, different IODP are not retained just because the message type is different. If the IODP for a message type has been updated, all of the IODP for other message types that are transmitted are then updated. If a message type that references a new IODP appears before a message type 1 containing a new PRN mask has been received, that message type must not be used until a compatible PRN mask has been received. Once a new compatible PRN mask has been received, those messages may be used immediately. In order to protect against message type 1 reception failures, when the PRN mask is updated, message type 1 containing new PRN mask is transmitted at least four times over a period of 600 seconds before other message types that reference the new PRN mask are transmitted. In addition, PRN mask updating is never performed more frequently than once per hour.
Table 5.4.3-2 Message Type 1: PRN Mask Data Repetitions Content Number of bits Resolution Effective Range Units
210 PRN mask 1 1 0~1 ―
1 IODP 2 1 0~3 ―
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Table 5.4.3-3 PRN Slot Assignments to GNSS Satellites PRN Slot Satellite System
1~37 GPS
38~61 GLONASS
62~119 (Spare)
120~138 SBAS
139~182 (Spare)
183 Quasi Zenith Satellite #1 L1-SAIF
184 Quasi Zenith Satellite #2 L1-SAIF
185 Quasi Zenith Satellite #3 L1-SAIF
186 Quasi Zenith Satellite #4 L1-SAIF
187 Quasi Zenith Satellite #5 L1-SAIF
188~192 Spare (for Quasi Zenith Satellite)
193 Quasi Zenith Satellite #1 L1C/A
194 Quasi Zenith Satellite #2 L1C/A
195 Quasi Zenith Satellite #3 L1C/A
196 Quasi Zenith Satellite #4 L1C/A
197 Quasi Zenith Satellite #5 L1C/A
198~202 Spare (for Quasi Zenith Satellite)
203~210 (Spare)
5.4.3.3.3 Message Types 2 - 5 (Fast Correction & UDRE)
Message types 2 - 5 are used to transmit fast correction data. Each message has 13 correction data slots, each corresponding to the following PRN mask numbers: Message type 2 PRN mask no. 1 - 13 Message type 3 PRN mask no. 14 - 26 Message type 4 PRN mask no. 27 - 39 Message type 5 PRN mask no. 40 - 51 Slot 13 in message type 5 is not used. Each fast correction message type is transmitted only when needed by the number of satellites specified in the PRN mask. In other words, message type 5 is transmitted only when 40 or more satellites have been specified. The 12-bit fast correction (FCi) is expressed as a two’s complement number (the MSB is the sign bit) and has a resolution of 0.125 m for the range of [-256.000 m, +255.750 m]. If this range is exceeded, FCi = 255.875 m and UDREIi = 15 will be set so as to prohibit use of fast correction. As message types 2 - 5 always have 13 correction slots, data for extra slots with no corresponding PRN mask numbers should never be used. The FCi valid time (ti,0f) is the starting point for the second epoch of GPS time that matches the first bit of the message block. An "invalid" value for the fast correction value means that FCi = 255.875 or there is a time-out status. If fast correction is invalid or UDREIi =14-15, the associate satellite shall not be used for position computation. The UDREIi included in message types 2 - 5 and 24 indicates the σ2
i,UDRE corresponding to the fast correction and is used to calculate the protection level. UDREIi = 15 indicates that the use
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of that satellite is prohibited. UDREIi may also be transmitted by message type 6. In such cases, IODFj shows the timing by which this corresponds to the FCi that is transmitted. Message types 2 - 5 and 24 include a 2-bit fast correction updating number (IODFj). Here "j" indicates the message type number (2 - 5); in the case of message type 24, it indicates the message type (2 - 5) to which it corresponds. IODFj is used when calculating the degree of degradation of the fast correction time change rate RRCi, and to establish the correspondence with the UDREIi included in message type 6. If there is no alert status for any of the satellites in the correction slots, the range of the IODFj counter is 0 - 2 (incremented one by one; 2 is followed by 0). If an alert has been generated for one or more of the satellites in the correction slots, the IODFj value is set to 3. If IODFj = 3 has been transmitted, it indicates that the UDREIi included in that message type is used for all of the fast corrections that are effective (i.e., not in time-out status) at that time. If there are no more than 6 correction slots, message type 24 (combined fast & long-term corrections message) is used in place of message types 2 - 5.
Table 5.4.3-4 Message Types 2 - 5: Fast Correction Repetitions Content Number of bits Resolution Effective Range Units
1 IODFj 2 1 0~3 ―
1 IODP 2 1 0~3 ―
13 FCi 12* 0.125 -256~ +255.75 m
13 UDREIi 4 (See Table 5.4.3-5)
*: Parameters so indicated shall be in two’s complement notation.
Table 5.4.3-5 UDRE value UDREIi σ2
i,UDRE(m2) UDREIi σ2i,UDRE(m2)
0 0.0520 8 2.5465
1 0.0924 9 3.3260
2 0.1444 10 5.1968
3 0.2830 11 20.7870
4 0.4678 12 230.9661
5 0.8315 13 2078.695
6 1.2992 14 Not Monitored
7 1.8709 15 Do Not Use
5.4.3.3.4 Message Type 6 (Integrity Data)
Message type 6 has been prepared to broadcast integrity data. The UDREIi for all satellites that are targeted for augmentation (for which a PRN mask has been set) are transmitted together using the format shown in Table 5.4.3-5 and Table 5.4.3-6. Message type 6 also includes an IODFj; an updated number for the fast correction data is displayed for each of the 13 correction slots as in message types 2 - 5.
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Table 5.4.3-6 Message Type 6: Integrity Data Repetitions Content Number of bits Resolution Effective Range Units
1 IODF2 2 1 0~3 ―
1 IODF3 2 1 0~3 ―
1 IODF4 2 1 0~3 ―
1 IODF5 2 1 0~3 ―
51 UDREIi 4 (See Table 5.4.3-5)
5.4.3.3.5 Message Type 7 (Fast Correction Degradation Factor)
Message type 7 is broadcast for maintaining compatibility, and described in Table 5.4.3-7.
Table 5.4.3-7 Message Type 7: Fast Correction Degradation Factor Repetitions Content Number of bits Resolution Effective Range Units
1 System delay(tlat) 4 1 0~15 s
1 IODP 2 1 0~3 ―
206 All zero 1 1 0
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5.4.3.3.6 Message Type 10 (Degradation Parameter)
Message type 10 has been designed to provide a degradation factor used to calculate the protection level. The parameters are as shown in Table 5.4.3-8.
Table 5.4.3-8 Message Type 10: Degradation Parameter Repetitions Content Number of bits Resolution Effective Range Units
1 Brrc 10 0.002 0~2.046 m
1 Cltc_lsb 10 0.002 0~2.046 m
1 Cltc_v1 10 0.05 0~51.15 mm/s
1 Iltc_v1 9 1 0~511 s
1 Cltc_v0 10 0.002 0~2.046 m
1 Iltc_v0 9 1 0~511 s
1 Cgeo_lsb 10 0.5 0~511.5 mm
1 Cgeo_v 10 0.05 0~51.15 mm/s
1 Igeo 9 1 0~511 s
1 Cer 6 0.5 0~31.5 m
1 Ciono_step 10 0.001 0~1.023 m
1 Iiono 9 1 0~511 s
1 Ciono_ramp 10 0.005 0~5.115 mm/s
1 RSSUDRE 1 1 0~1 ―
1 RSSiono 1 1 0~1 ―
1 Ccovariance 7 0.1 0~12.7 ―
1 Cqzs_lsb 10 0.002 0~2.046 m
1 Cqzs_v1 10 0.05 0~51.15 mm/s
1 Iqzs_v1 9 1 0~511 s
1 Cqzs_v0 10 0.002 0~2.046 m
1 Iqzs_v0 9 1 0~511 s
1 IRI 3 1 0~4 ―
1 Spare 30 ― ― ―
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5.4.3.3.7 Message Type 18 (IGP Mask)
As correction data for the ionospheric propagation delay, vertical delays corresponding to the predetermined ionosphere grid points (IGP) are transmitted. Message type 18 is used to specify the IGP that is currently the reference point for augmentation. Message type 18 must be received before ionospheric propagation delay correction is performed. Table 5.4.3-9 and Table 5.4.3-10 show the format and IGP content, respectively, for message type 18. The IGP is divided into 10 bands that are assigned band numbers 0 - 9. For each band, as many as 201 IGPs are defined, corresponding to slots 1 - 201. The order of IGP assignment for each band begins with slot number 1 in the southwest corner and increments from south to north along the same longitude. Once the northern edge is reached, it increments along the next eastward longitude from south to north and so on in sequence to assign the IGP slot numbers from 1 - 201. IGPs for which IGP masks have been set are divided into blocks of 15 (up to 14 blocks) in sequence by IGP mask number. IGP block 0 corresponds to IGP mask number 1 - 15, IGP block 1 corresponds to IGP mask number 16 - 30 and so on. The receiver need only collect correction data for the IGPs located at ± 20° in latitude and longitude from its location. If the number of bands transmitted by message type 18 is 0, it indicates that ionospheric propagation delay correction data are not provided. Message type 18 includes a 2-bit IGP mask update number (IODI). This number is incremented each time the IGP mask is updated (note that, since the IODI is only 2-bits, after 3 comes 0). Message type 26 includes an IODI that corresponds to the IGP mask that should be used by the receiver, so the receiver should constantly monitor the IGP mask that the IODI matches and convert it into an IGP slot number. IGP masks are almost never updated. Nevertheless, message type 26 always requires an effective IGP mask, so a new IGP mask is transmitted by means of message type 18 before the IODI for message type 26 is updated. When a new IGP mask is received, the receiver should retain both old and new IGP masks for some time. It is important to use the appropriate IGP mask while waiting for the IODI for message type 26 to be updated. In the event that a new message type 26 referencing a new IODI has appeared before a message type 18 containing a new IGP mask is received, that message type 26 must not be used until a compatible IGP mask is received. Once a compatible IGP mask has been received, the message type 26 may be used immediately. In order to prepare for message type 18 reception failures, when the IGP mask is updated, message type 18 is broadcast at least four times over a period of 600 seconds before a message type 26 referencing the new IGP mask is transmitted. In addition, IGP mask updating is never performed more frequently than once per hour.
Table 5.4.3-9 Message Type 18 Format: IGP Mask Repetitions Content Number o bits Resolution Effective Range Units
1 No. of IGP bands 4 1 0~11 ―
1 IGP band no. 4 1 0~10 ―
1 IODIk 2 1 0~3 ―
201 IGP mask 1 ― 0~1 ―
1 IGP mask pattern 1 ― 0~1 ―
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Table 5.4.3-10 Specification of IGP locations
(IGP mask pattern = 0)
Band Longitude Latitude Slot No.
0 180W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N,85N 1~28
175W 55S,50S,45S,...,45N,50N,55N 29~51
170W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 52~78
165W 55S,50S,45S,...,45N,50N,55N 79~101
160W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 102~128
155W 55S,50S,45S,...,45N,50N,55N 129~151
150W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 152~178
145W 55S,50S,45S,...,45N,50N,55N 179~201
1 140W 85S,75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~28
135W 55S,50S,45S,...,45N,50N,55N 29~51
130W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 52~78
125W 55S,50S,45S,...,45N,50N,55N 79~101
120W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 102~128
115W 55S,50S,45S,...,45N,50N,55N 129~151
110W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 152~178
105W 55S,50S,45S,...,45N,50N,55N 179~201
2 100W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~27
95W 55S,50S,45S,...,45N,50N,55N 28~50
90W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N,85N 51~78
85W 55S,50S,45S,...,45N,50N,55N 79~101
80W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 102~128
75W 55S,50S,45S,...,45N,50N,55N 129~151
70W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 152~178
65W 55S,50S,45S,...,45N,50N,55N 179~201
3 60W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~27
55W 55S,50S,45S,...,45N,50N,55N 28~50
50W 85S,75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 51~78
45W 55S,50S,45S,...,45N,50N,55N 79~101
40W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 102~128
35W 55S,50S,45S,...,45N,50N,55N 129~151
30W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 152~178
25W 55S,50S,45S,...,45N,50N,55N 179~201
4 20W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~27
15W 55S,50S,45S,...,45N,50N,55N 28~50
10W 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 51~77
5W 55S,50S,45S,...,45N,50N,55N 78~100
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0 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N,85N 101~128
5E 55S,50S,45S,...,45N,50N,55N 129~151
10E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 152~178
15E 55S,50S,45S,...,45N,50N,55N 179~201
5 20E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~27
25E 55S,50S,45S,...,45N,50N,55N 28~50
30E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 51~77
35E 55S,50S,45S,...,45N,50N,55N 78~100
40E 85S,75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 101~128
45E 55S,50S,45S,...,45N,50N,55N 129~151
50E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 152~178
55E 55S,50S,45S,...,45N,50N,55N 179~201
6 60E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~27
65E 55S,50S,45S,...,45N,50N,55N 28~50
70E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 51~77
75E 55S,50S,45S,...,45N,50N,55N 78~100
80E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 101~127
85E 55S,50S,45S,...,45N,50N,55N 128~150
90E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N,85N 151~178
95E 55S,50S,45S,...,45N,50N,55N 179~201
7 100E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~27
105E 55S,50S,45S,...,45N,50N,55N 28~50
110E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 51~77
115E 55S,50S,45S,...,45N,50N,55N 78~100
120E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 101~127
125E 55S,50S,45S,...,45N,50N,55N 128~150
130E 85S,75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 151~178
135E 55S,50S,45S,...,45N,50N,55N 179~201
8 140E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~27
145E 55S,50S,45S,...,45N,50N,55N 28~50
150E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 51~77
155E 55S,50S,45S,...,45N,50N,55N 78~100
160E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 101~127
165E 55S,50S,45S,...,45N,50N,55N 128~150
170E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 151~177
175E 55S,50S,45S,...,45N,50N,55N 178~200
9 60N 180W,175W,170W,...,165E,170E,175E 1~72
65N 180W,170W,160W,...,150E,160E,170E 73~108
70N 180W,170W,160W,...,150E,160E,170E 109~144
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75N 180W,170W,160W,...,150E,160E,170E 145~180
85N 180W,150W,120W,...,90E,120E,150E 181~192
10 60S 180W,175W,170W,...,165E,170E,175E 1~72
65S 180W,170W,160W,...,150E,160E,170E 73~108
70S 180W,170W,160W,...,150E,160E,170E 109~144
75S 180W,170W,160W,...,150E,160E,170E 145~180
85S 170W,140W,110W,...,100E,130E,160E 181~192
(IGP mask pattern = 1)
Band Longitude Latitude Slot No.
0 115E 15N,16N,17N,...,33N,34N,35N 1~21
116E 15N,16N,17N,...,33N,34N,35N 22~42
117E 15N,16N,17N,...,33N,34N,35N 43~63
118E 15N,16N,17N,...,33N,34N,35N 64~84
119E 15N,16N,17N,...,33N,34N,35N 85~105
120E 15N,16N,17N,...,43N,44N,45N 106~136
121E 15N,16N,17N,...,43N,44N,45N 137~167
122E 15N,16N,17N,...,43N,44N,45N 168~198
1 123E 15N,16N,17N,...,43N,44N,45N 1~31
124E 15N,16N,17N,...,43N,44N,45N 32~62
125E 15N,16N,17N,...,43N,44N,45N 63~93
126E 15N,16N,17N,...,43N,44N,45N 94~124
127E 15N,16N,17N,...,43N,44N,45N 125~155
128E 15N,16N,17N,...,43N,44N,45N 156~186
2 129E 15N,16N,17N,...,43N,44N,45N 1~31
130E 15N,16N,17N,...,48N,49N,50N 32~67
131E 15N,16N,17N,...,48N,49N,50N 68~103
132E 15N,16N,17N,...,48N,49N,50N 104~139
133E 15N,16N,17N,...,48N,49N,50N 140~175
3 134E 15N,16N,17N,...,48N,49N,50N 1~36
135E 15N,16N,17N,...,53N,54N,55N 37~77
136E 15N,16N,17N,...,53N,54N,55N 78~118
137E 15N,16N,17N,...,53N,54N,55N 119~159
138E 15N,16N,17N,...,53N,54N,55N 160~200
4 139E 15N,16N,17N,...,53N,54N,55N 1~41
140E 15N,16N,17N,...,53N,54N,55N 42~82
141E 20N,21N,22N,...,53N,54N,55N 83~118
142E 20N,21N,22N,...,53N,54N,55N 119~154
143E 20N,21N,22N,...,53N,54N,55N 155~190
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5 144E 20N,21N,22N,...,53N,54N,55N 1~36
145E 20N,21N,22N,...,53N,54N,55N 37~72
146E 20N,21N,22N,...,53N,54N,55N 73~108
147E 20N,21N,22N,...,53N,54N,55N 109~144
148E 20N,21N,22N,...,53N,54N,55N 145~180
6 149E 20N,21N,22N,...,53N,54N,55N 1~36
150E 20N,21N,22N,...,53N,54N,55N 37~72
151E 25N,26N,27N,...,53N,54N,55N 73~103
152E 25N,26N,27N,...,53N,54N,55N 104~134
153E 25N,26N,27N,...,53N,54N,55N 135~165
154E 25N,26N,27N,...,53N,54N,55N 166~196
7 100E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~27
105E 55S,50S,45S,...,45N,50N,55N 28~50
110E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 51~77
115E 55S,50S,45S,...,45N,50N,55N 78~100
120E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 101~127
125E 55S,50S,45S,...,45N,50N,55N 128~150
130E 85S,75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 151~178
135E 55S,50S,45S,...,45N,50N,55N 179~201
8 140E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 1~27
145E 55S,50S,45S,...,45N,50N,55N 28~50
150E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 51~77
155E 55S,50S,45S,...,45N,50N,55N 78~100
160E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 101~127
165E 55S,50S,45S,...,45N,50N,55N 128~150
170E 75S,65S,55S,50S,45S,...,45N,50N,55N,65N,75N 151~177
175E 55S,50S,45S,...,45N,50N,55N 178~200
9 110E 17.5N,22.5N,27.5N,32.5N,37.5N 1~5
112.5E 15N,17.5N,20N,...,35N,37.5N,40N 6~16
115E 17.5N,22.5N,27.5N,32.5N,37.5N 17~21
117.5E 15N,17.5N,20N,...,35N,37.5N,40N 22~32
120E 17.5N,22.5N,27.5N,32.5N,37.5N,42.5N 33~38
122.5E 15N,17.5N,20N,...,40N,42.5N,45N 39~51
125E 17.5N,22.5N,27.5N,32.5N,37.5N,42.5N 52~57
127.5E 15N,17.5N,20N,...,40N,42.5N,45N 58~70
130E 17.5N,22.5N,27.5N,32.5N,37.5N,42.5N,47.5N,52.5N 71~78
132.5E 15N,17.5N,20N,...,50N,52.5N,55N 79~95
135E 17.5N,22.5N,27.5N,32.5N,37.5N,42.5N,47.5N,52.5N 96~103
137.5E 15N,17.5N,20N,...,50N,52.5N,55N 104~120
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140E 17.5N,22.5N,27.5N,32.5N,37.5N,42.5N,47.5N,52.5N 121~128
142.5E 15N,17.5N,20N,...,50N,52.5N,55N 129~145
145E 17.5N,22.5N,27.5N,32.5N,37.5N,42.5N,47.5N,52.5N 146~153
147.5E 20N,22.5N,25N,...,50N,52.5N,55N 154~168
150E 22.5N,27.5N,32.5N,37.5N,42.5N,47.5N,52.5N 169~175
152.5E 25N,27.5N,30N,...,50N,52.5N,55N 176~188
155E 27.5N,32.5N,37.5N,42.5N,47.5N,52.5N 189~194
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5.4.3.3.8 Message Type 24 (Mixed Fast/Long-term Correction)
Message type 24 may be used when the correction slot in message types 2 - 5 can only accommodate up to 6 items. Specifically, this occurs when the number of satellites subject to augmentation is 1 - 6, 14 - 19, 27 - 32 or 40 - 45. The first half of message type 24 contains the fast correction data in six slots. The 0 - 3 values for block ID correspond to message types 2 - 5, respectively, and specify the range of the PRN mask number to which the fast corrections in the six correction slots correspond. The method of use for the fast corrections is exactly the same as that for message types 2 - 5. The last half of message type 24 can accommodate half of the content of message type 25 (partial message). This allows long-term correction data for one or two satellites to be provided.
Table 5.4.3-11 Message Type 24 (Fast & Long-term Corrections) Repetitions Content Number of bits Resolution Effective Range Units
6 FCi 12* 0.125 -256~+255.75 m
6 UDREIi 4 (See Table 5.4.3-5)
1 IODP 2 1 0~3 ―
1 Fast correction block ID 2 1 0~3 ―
1 IODFj 2 1 0~3 ―
1 Reserved 4 - - -
1 Partial message 106 (See Table 5.4.3-13)
*: Parameters so indicated shall be in two’s complement notation.
5.4.3.3.9 Message Type 25 (Long-Term Correction)
Message type 25 is broadcast to provide corrections for the clock and ephemeris long-term error. For GPS satellites, the clock and ephemeris that are the target for augmentation using QZS message type 25 must be calculated using the L1C/A navigation message (NAV message). The CNAV and CNAV2 messages must not be used. Message type 25 is made up of two partial messages. Each partial message has exactly the same format consisting of 106 bits. The partial message may include correction data for two satellites (velocity code = 0) or correction data for one satellite (velocity code = 1). In the former case (velocity code = 0), the message includes only corrections for clock offset and satellite position error. In the latter case, the message also includes the rates of change for clock offset and satellite positioning errors. Therefore, a message type 25 can accommodate long-term correction data for 2 - 4 satellites. Table 5.4.3-13 specifies the format for the two types of partial message corresponding to velocity code values of "0" and "1". The velocity codes for the two partial messages included in a single message of message type 25 can be different value. The PRN mask number (1 - 51) is defined by the PRN mask provided by message type 1. The IODP for the PRN mask must match. If the long-term correction data are invalid, "0" is set for the PRN mask number. Unlike message types 2 - 5, the positioning satellites augmented by message type 25 may not appear in sequential order, and there is no guarantee that the long-term corrections for each satellite will appear with the same frequency. Long-term correction data for satellites with rapidly changing long-term errors will be repeated with a greater frequency than the data of satellites with long-term errors that change more slowly.
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Table 5.4.3-12 Message Type 25: Long-Term Correction Repetitions Content Number of bits Resolution Effective Range Units
2 Partial message 106 (See Table 5.4.3-13)
Table 5.4.3-13 Partial message format of Message Type 25 (Velocity code=0)
Repetitions Content Number of bits Resolution Effective Range Units
1 Velocity code(=0) 1 1 0 ―
2
PRN mask no. 6 1 1~51 ―
IODi** 8 1 0~255 ―
xi 9* 0.125 ±32 m
yi 9* 0.125 ±32 m
zi 9* 0.125 ±32 m
ai,f0 10* 2-31 ±2-22 s
1 IODP 2 1 0~3 ―
1 Spare 1 ― ― ―
(Velocity code=1)
Repetitions Content Number of bits Resolution Effective Range Units
1 Velocity code(=1) 1 1 1 ―
1
PRN mask no. 6 1 1~51 ―
IODi** 8 1 0~255 ―
xi 11* 0.125 ±128 m
yi 11* 0.125 ±128 m
zi 11* 0.125 ±128 m
ai,f0 11* 2-31 ±2-21 s
x.
i 8* 2-11 ±0.0625 m/s
y.
i 8* 2-11 ±0.0625 m/s
z.
i 8* 2-11 ±0.0625 m/s
ai,f1 8* 2-39 ±2-32 s/s
1 Epoch time(ti,LT) 13 16 0~86384 s
1 IODP 2 1 0~3 ―
* Parameters so indicated are in two’s complement notation.
**The Issue of Data value corresponds to the 8-bit GPS Ephemeris IOD value.
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An 8-bit Issue of Data value (IOD) is included in the long-term correction data. User receivers must only use navigation messages containing IODC and IODE values that match this number (in the case of IODC, applied to the last 8 bits). If these do not match, it indicates that the GPS navigation message has been updated; however, the receiver should continue to use the old navigation message (for which the IOD matches). If a message type 24 or 25 that matches the new navigation message IOD has been received, the receiver should switch to the new navigation message for positioning. Some time will be required for all user receivers to receive the new navigation message. For this reason, even if the IOD for the GPS navigation message has been updated, the long-term correction data IOD provided by message type 24 and 25 will not be updated for at least two minutes.
5.4.3.3.10 Message Type 26 (Ionospheric Delay & GIVE)
Message type 26 provides receivers with augmentation data corresponding to the IGP defined in Table 5.4.3-9. This includes the ionospheric vertical delay (at the L1 frequency) and its accuracy. For more information on the content of the data, see Table 5.4.3-14. The correspondence between GIVEI and σ2
GIVE is as shown in Table 5.4.3-15. A single message of type 26 provides 15 items of augmentation data for a given IGP. A band number (0 - 9) and a block ID (0 - 13) are also included to specify the corresponding IGP. The band number corresponds to the band numbers in Table 5.4.3-10. Block 0 corresponds to IGP mask numbers 1 - 15 (numbers 1 - 15 of the IGPs for which the IGP mask number is set to "1"). Block 1 corresponds to IGP mask numbers 16 - 30. Augmentation data located at slot numbers that exceed the number of IGPs indicated by the IGP mask data are invalid. The 9-bit ionospheric vertical delay parameter has a resolution of 0.125 m in the effective range of [0, 63.750 m]. A vertical delay of 63.875 m (111111111) indicates "use prohibited”. In other words, a vertical delay exceeding 63.750 m cannot be expressed.
Table 5.4.3-14 Message Type 26: Ionospheric Delay Correction Repetitions Content Number of bits Resolution Effective Range Units
1 IGP band ID 4 1 0~9 ―
1 IGP block ID 4 1 0~13 ―
15 Ionospheric vertical delay 9 0.125 0~63.750 m
GIVEIi 4 (See Table 5.4.3-15)
1 IODIk 2 1 0~3 ―
1 Spare 7 ― ― ―
Table 5.4.3-15 GIVEI Value GIVEIi σ2
GIVE,i(m2) GIVEIi σ2GIVE,i(m2)
0 0.0084 8 0.6735
1 0.0333 9 0.8315
2 0.0749 10 1.1974
3 0.1331 11 1.8709
4 0.2079 12 3.3260
5 0.2994 13 20.7870
6 0.4075 14 187.0826
7 0.5322 15 Not Monitored
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5.4.3.3.11 Message Type 28 (Clock-ephemeris Covariance)
Message type 28 is transmitted to provide the covariance matrix that expresses the correlation between clock and ephemeris error. Using this matrix makes it possible to estimate the degree of degradation of correction data at the receiver position. Table 5.4.3-16 specifies the content and format of message type 28. The PRN mask number is the same as that for message types 24 and 25. Message type 28 includes covariance matrices for two satellites. However, there is only one IODP, and the same PRN mask data are used for both satellites.
Table 5.4.3-16 Message Type 28: Clock - Orbit Covariance
Repetitions Content Number of
bits Resolution
Effective
Range Units
1 IODP 2 1 0~3 ―
2
PRN mask no. 6 1 1~51 ―
Scale factor 3 1 0~7 ―
E1,1 9 1 0~511 ―
E2,2 9 1 0~511 ―
E3,3 9 1 0~511 ―
E4,4 9 1 0~511 ―
E1,2 10* 1 ±512 ―
E1,3 10* 1 ±512 ―
E1,4 10* 1 ±512 ―
E2,3 10* 1 ±512 ―
E2,4 10* 1 ±512 ―
E3,4 10* 1 ±512 ―
*: Parameters so indicated shall be in two’s complement notation.
5.4.3.3.12 Message Types 62 (Internal Test Message) and 63 (Null Message)
Message type 63 is the Null Message and is always transmitted as a string of 212 zeroes. Message type 62 is used only for internal testing purposes, and its content is not defined.
Table 5.4.3-17 Message Type 63 (Null Message)
Repetitions Content Number of
bits Resolution
Effective
Range Units
212 All zeroes 1 1 0 ―
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5.4.3.4 Message Content (SBAS Non-Compatible Message)
5.4.3.4.1 Message Type 52 (TGP Mask)
As correction data for the tropospheric delay, Zenith Tropospheric Delay Offset (ZTDO) at the tropospheric grid point (TGP) is transmitted. Message type 52 is used to specify the TGPs that provide ZTDOs. Table 5.4.3-18 specifies the content of message type 52. Message type 52 includes 2 bit TGP issue mask update number (IODT). This number is incremented each time the TGP Mask is updated. (note: after 3 comes 0) Message type 53 contains the same IODT as message type52. The correction data should be applied with confirmation of the correspondence of IODT between message type 52 and 53 in receivers. All the received correction data could be applied by retaining un-updated mask data until receiving all the messages type 52 and 53 coming after IODT update. The TGPs which provide ZTDOs are specified by using 210 slots in message 52. Table 5.4.3-19 shows the TGP number and its corresponding longitude and latitude. Slot of which position is the same number as TGP number which provides ZTDO is set as ‘1’. Message type 52 is transmitted at least 1 time over a period of 600 seconds.
Table 5.4.3-18 Message Type 52:TGP Mask
Repetitions Content Number of
bits Resolution
Effective
Range Units
1 IODT 2 1 0~3 -
210 TGP Mask 1 1 0~1 -
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Table 5.4.3-19 Specification of TGP locations TGP Number
East Longitude
North Latitude
TGP Number
East Longitude
North Latitude
TGP Number
East Longitude
North Latitude
1 144.5 44.0 36 138.5 36.0 71 145.0 44.0 2 144.5 43.5 37 137.5 36.5 72 145.0 43.5 3 142.5 45.0 38 139.0 35.0 73 145.0 43.0 4 144.0 43.5 39 138.0 35.5 74 143.0 44.5 5 142.5 44.5 40 137.0 36.0 75 144.5 43.0 6 144.0 43.0 41 139.5 33.5 76 143.0 44.0 7 143.0 43.5 42 137.5 35.0 77 142.0 44.5 8 142.5 43.5 43 136.5 35.5 78 143.5 43.0 9 142.0 43.5 44 136.0 35.5 79 143.0 43.0 10 141.5 43.5 45 135.5 35.5 80 142.5 43.0 11 143.0 42.0 46 135.0 35.5 81 142.0 43.0 12 141.5 42.5 47 134.5 35.5 82 141.5 43.0 13 140.5 43.0 48 136.0 34.0 83 141.0 43.0 14 141.5 41.0 49 135.0 34.5 84 141.0 42.0 15 141.0 41.5 50 133.5 35.5 85 140.5 42.0 16 142.0 40.0 51 135.0 34.0 86 141.0 41.0 17 141.0 40.5 52 133.5 35.0 87 140.0 42.0 18 140.0 41.5 53 142.0 26.5 88 141.5 40.0 19 141.5 39.5 54 134.0 34.0 89 140.5 40.5 20 141.0 39.5 55 133.0 34.5 90 140.0 40.5 21 140.5 39.5 56 132.0 35.0 91 141.5 39.0 22 140.0 39.5 57 133.5 33.5 92 141.0 39.0 23 141.0 38.0 58 133.0 33.5 93 140.5 39.0 24 140.5 38.0 59 132.5 33.5 94 140.0 39.0 25 140.0 38.0 60 131.5 34.0 95 141.0 37.5 26 139.5 38.5 61 131.5 33.5 96 140.5 37.5 27 140.5 37.0 62 131.0 33.5 97 139.5 38.0 28 140.0 37.0 63 130.5 33.5 98 139.0 38.0 29 139.0 37.5 64 130.0 33.5 99 140.5 36.5 30 140.5 36.0 65 131.5 32.0 100 139.5 37.0 31 139.5 36.5 66 130.5 32.5 101 138.5 37.5 32 138.5 37.0 67 129.5 33.0 102 140.0 36.0 33 140.0 35.5 68 131.0 31.5 103 139.0 36.5 34 139.0 36.0 69 130.5 31.0 104 138.0 37.0 35 137.0 37.5 70 128.0 26.5 105 139.5 35.5
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TGP Number
East Longitude
North Latitude
TGP Number
East Longitude
North Latitude
TGP Number
East Longitude
North Latitude
106 137.5 37.0 141 145.5 43.5 176 138.0 36.5 107 139.0 35.5 142 144.0 44.0 177 137.0 37.0 108 138.0 36.0 143 142.0 45.5 178 138.5 35.5 109 137.0 36.5 144 143.5 44.0 179 137.5 36.0 110 138.5 35.0 145 142.0 45.0 180 136.5 36.5 111 137.5 35.5 146 143.5 43.5 181 138.0 35.0 112 136.5 36.0 147 142.5 44.0 182 137.0 35.5 113 138.0 34.5 148 142.0 44.0 183 136.0 36.0 114 137.0 35.0 149 143.5 42.5 184 137.5 34.5 115 136.5 35.0 150 143.0 42.5 185 137.0 34.5 116 136.0 35.0 151 142.5 42.5 186 136.5 34.5 117 135.5 35.0 152 142.0 42.5 187 136.0 34.5 118 135.0 35.0 153 141.0 42.5 188 135.5 34.5 119 134.0 35.5 154 140.5 42.5 189 134.5 35.0 120 135.5 34.0 155 140.0 42.5 190 136.0 33.5 121 134.0 35.0 156 141.5 40.5 191 134.5 34.5 122 135.5 33.5 157 140.5 41.0 192 133.0 35.5 123 134.0 34.5 158 142.0 39.5 193 134.5 34.0 124 133.0 35.0 159 141.0 40.0 194 133.5 34.5 125 134.5 33.5 160 140.5 40.0 195 132.5 35.0 126 133.5 34.0 161 140.0 40.0 196 134.0 33.5 127 132.5 34.5 162 141.5 38.5 197 133.0 34.0 128 132.0 34.5 163 141.0 38.5 198 132.5 34.0 129 131.5 34.5 164 140.5 38.5 199 132.0 34.0 130 133.0 33.0 165 140.0 38.5 200 131.0 34.5 131 132.5 33.0 166 141.0 37.0 201 131.0 34.0 132 132.0 33.0 167 140.0 37.5 202 130.5 34.0 133 131.5 33.0 168 139.5 37.5 203 129.5 34.5 134 131.0 33.0 169 138.5 38.0 204 131.5 32.5 135 130.5 33.0 170 140.0 36.5 205 131.0 32.5 136 129.5 33.5 171 139.0 37.0 206 130.0 33.0 137 131.0 32.0 172 140.5 35.5 207 131.5 31.5 138 130.0 32.5 173 139.5 36.0 208 130.5 32.0 139 129.0 33.0 174 138.5 36.5 209 130.5 31.5 140 131.0 30.5 175 140.0 35.0 210 129.0 28.0
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5.4.3.4.2 Message Type 53 (Tropospheric Delay Correction)
By the message type 53, ZTDO at TGP which is specified by TGP mask data of message type 52 is transmitted to the receivers. Table 5.4.3-20 shows the data content. One message type 53 contains 2bits IODT, 3 bits TGP block ID, and ZTDOs at 34 TGPs. Total number of TGPs which provide ZTDOs is obtained by the mask data of message type 52. Message type 53 with TGP block ID from 0 to an integer n is provided, where the total number of TGPs to provide ZTDOs is larger than 34n and no more than 34 1n . The message type 53 with TGP block ID n contains ZTDOs at from 34 1n th to 34 1n th TGPs in the same order as in the effective TGP mask data. ZTDO which is provided 6 bits per 1 point has a resolution of 0.01m in the effective range of [-0.32, 0.30m]. 011111 indicates that ZTDO of corresponding TGP has not been provided.
Table 5.4.3-20 Message type 53:Zenith Tropospheric Delay Correction
Repetitions Content Number of
bits Resolution
Effective
Range Units
1 IODT 2 1 0~3 -
1 TGP block ID 3 1 0~6 -
34 ZTDO 6* 0.01 -0.32~0.30 m
1 Reserved 3 - - -
*:Parameters shall be in two’s complement notation.
5.4.3.4.3 Message Type 54 (Atmospheric Delay Correction)
Content has not been defined yet.
5.4.3.4.4 Message Type 55 (Atmospheric Delay Correction)
Content has not been defined yet.
5.4.3.4.5 Message Type 56 (Inter Signal Bias Correction Data)
Message type 56 provides the internal signal group delay with respect to the L1C/A signal for the timing at which the multiple signals broadcast by the corresponding GPS or QZSS satellite are actually transmitted from the phase center of the satellite antenna. The PRN mask number has the same meaning as that for message type 25. When multiple signals are used together, the data in this message can be used.
Table 5.4.3-21 Message Type 56: Inter Signal Bias Correction Data
Repetitions Content Number of
bits Resolution
Effective
Range Units
1 IODP 2 1 0~3 ―
5
PRN mask no. 6 1 1~51 ―
ISCL1C_L1CA 9* 0.05 ±12.8 m
ISCL2C_L1CA 9* 0.05 ±12.8 m
ISCL5_L1CA 9* 0.05 ±12.8 m
ISCL1P_L1CA 9* 0.05 ±12.8 m
*: Parameters so indicated shall be in two’s complement notation.
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5.4.3.4.6 Message Type 57 (Orbit Data)
Content has not been defined yet.
5.4.3.4.7 Message Type 58 (QZS Ephemeris)
Message type 58 is transmitted to provide QZS Ephemeris data. The satellite position is provided in the form of coordinates in the Japan satellite navigation Geodetic System (JGS) orthogonal coordinate system in reference epoch t0,Q.
Table 5.4.3-22 QZS Ephemeris Data Item Number of bits Range Resolution Notes
t0,Q 8 0-10740s 60s Epoch time
URA 4 0-15 - Positioning accuracy indicator
QX 26* ±42949.673 km 1.28 m X coordinate
QY 26* ±42949.673 km 1.28 m Y coordinate
QZ 26* ±42949.673 km 1.28 m Z coordinate
QX 24* ±4194.304 m/s 0.5 mm/s Velocity
QY 24* ±4194.304 m/s 0.5 mm/s Velocity
QZ 24* ±4194.304 m/s 0.5 mm/s Velocity
QX 5* ±32 μm/s 2 μm/s Acceleration
QY 5* ±32 μm/s 2 μm/s Acceleration
QZ 5* ±32 μm/s 2 μm/s Acceleration
aQf0 22* ±1.953 ms 2-30 s Clock correction
aQf1 13* ±3.725 ns/s 2-40 s/s Clock correction
Total 212
*: Parameters so indicated shall be in two’s complement notation.
5.4.3.4.8 Message Type 59 (QZSS Almanac Data)
Content has not been defined yet.
5.4.3.4.9 Message Type 60 ((Regional information/maintenance schedule))
Content has not been defined yet.
5.4.3.5 L1-SAIF+ Message
L1-SAIF+ Message is the message that Satellite Positioning Research and Application Center (SPAC) will transmit for the applications demonstration. For L1-SAIF+ Message, the message type 40 - 51 is defined as L1-SAIF+ Unique Message in addition to SBAS compatible message in Section 5.4.3.3, SBAS non- compatible message in Section 5.4.3.4. The detailed information are referenced in Interface Specification (Applicable Documents (6)) to be established by SPAC.
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5.5 L2C signal
5.5.1 RF characteristics
5.5.1.1 Signal configuration
In accordance with Section 5.1.
5.5.1.2 Carrier wave properties
In accordance with Section 5.1.
5.5.1.3 Code properties
5.5.1.3.1 Code attributes
Same as sections 3.2.1.4, 3.2.1.5 and 3.3.2.4 of Applicable Document (1). However, the PRN code number is as described in Section 5.1.1.11.1 of this document.
5.5.1.3.2 Non-standard code
In the event of a problem with QZSS, a non-standard code (NSC) is transmitted. This is done to protect users by ensuring that they do not receive or use erroneous navigation data.
5.5.2 Message
5.5.2.1 Message configuration
Each message of the L2C signal (DL2C) comprises 300 bits: 276 bits of data and 24 parity check bits. Each message is broadcast for 12 seconds. This message configuration is the same as in Applicable Document (1). 5.5.2.1.1 Preamble
The 8-bit preamble added to the beginning of each frame is the same as in Section 30.3.3 of Applicable Document (1).
5.5.2.1.2 PRN number
The 6-bit PRN number added after the preamble in each frame is the last 6 bits of the PRN number for the QZS transmitting the corresponding message.
5.5.2.1.3 Message type ID
The 6-bit message type ID added after the PRN number in each frame signifies the data contained in that frame. Table 5.5.2-1 specifies the message content for each of the individual message types. For more information, see Section 5.5.2.2. The different types of messages are transmitted at intervals not to exceed the Maximum Broadcast Periods specified in Table 5.5.2-2. QZSs may transmit the same message type with different timing.
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Table 5.5.2-1 Definitions of message types for Navigational Message DL2C Message type Message content Notes
10 Health, URA, Ephemeris 1
11 Ephemeris 2
30, 46 SV clock, ionospheric parameter, ISC
When value is 46: Rebroadcast of ionospheric parameters broadcasted by GPS, however ISC broadcasted by GPS is not rebroadcasted by QZSS
31, 47* SV clock, reduced Almanac When value is 47: Rebroadcast of GPS reduced Almanac
32 SV clock, EOP (Earth Orientation Parameter)
33, 49 SV clock, UTC parameter When value is 49: Rebroadcast of GPS UTC parameters
34 SV clock, performance enhancement data Transmitted as needed
35, 51 SV clock, GGTO (GPS GNSS Time Offset ) When value is 51: Rebroadcast of GGTO broadcasted by GPS
37, 53 SV clock, Midi Almanac When value is 53: Rebroadcast of GPS Midi Almanac
12*, 28 Reduced Almanac When value is 28: Rebroadcast of GPS reduced Almanac
13 SV clock performance enhancement data Transmitted as needed
14 Ephemeris performance enhancement data Transmitted as needed
15 Text Transmitted as needed * QZS-1 does not be broadcasting the data of Type 12 and 47 because the contents of them are same with those of type 31 and 28. Broadcasting the data of type 12 and 47 after "Phase Two" is under study
Table 5.5.2-2 Maximum Transmit periods for Navigational Message DL2C Message Data Message Type Maximum
broadcast Period Notes
Ephemeris 10,11 48 seconds
SV clock 30-35, 37, 46, 47, 49, 51, 53
48seconds
ISC, ionospheric parameter 30 288 seconds ISC, ionospheric parameter (GPS rebroadcasting)
46 *
Reduced Almanac of QZSS 31 or 12 20 minutes All necessary SV data must be transmitted
Reduced Almanac of GPS (GPS rebroadcasting)
47 or 28 * All necessary SV data must be transmitted
Midi Almanac of QZSS 37 120 minutes All necessary SV data must be transmitted
Midi Almanac of GPS (GPS rebroadcasting)
53 * All necessary SV data must be transmitted
EOP 32 30 minutes
UTC parameters 33 288 seconds
UTC parameters (GPS rebroadcasting) 49 *
DC data 34 or 13 & 14 30 minutes (*) Only when performance enhancement data are effective
GGTO (GPS-QZSS Time Offset) 35 288 seconds
GGTO (GPS-Galileo Time Offset) 51 *
Text 15 As needed * We will not define the maximum transmit period for GPS rebroadcasting parameters and GPS DC data.
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5.5.2.1.4 TOW count
The 17-bit TOW (Time of Week) count that follows the message type ID in each frame indicates the time at the beginning of the next frame, which is six times that value. This is the same as in Applicable Document (1).
5.5.2.1.5 "Alert" flag
The 1-bit "Alert" flag that follows the TOW count in each frame is in accordance with Section 5.1.2.1.3.
5.5.2.1.6 FEC and parity algorithm
The CNAV will be encoded with FEC. The algorithm for encoding is the same as in Section 3.3.3.1.1 of Applicable Document (1). The 24-bit parity code added after the 300-bit frame. The parity algorithm is the same as in Section 30.3.5 of Applicable Document (1).
5.5.2.2 Message content
With the exception of the list in Section 8.1.2, the content of the message is the same as in Applicable Document (1). 5.5.2.2.1 Ephemeris data and health for message types 10 and 11
5.5.2.2.1.1 Content of Ephemeris data and health for message types 10 and 11
Message types 10 and 11 include the Ephemeris data (such as that shown in Table 5.5.2-3) for the corresponding satellite. The general content is the same as in Section 30.3.3.1.1 of Applicable Document (1).
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Table 5.5.2-3 Definition of Ephemeris parameters for Navigational Message DL2C
Parameter Definition Difference from GPS definition
10 WNn Week Number
10 L1/L2/L5 Health L1, L2 and L5 signal health
10 top Data predict time of week (seconds into week)
10 URAoe index Ephemeris accuracy index
10 11
toe Ephemeris epoch (seconds into week)
10 A Difference from semi major axis at toe In the case of QZS, indicates difference with 42,164,200 [m]
In the case of GPS, indicates difference with 26,559,710 [m]
10 A Change rate in semi major axis
10 n0 Difference from mean motion calculation at toe
10 0n Change rate from mean motion calculation
10 M0-n Mean anomaly at toe
10 en Eccentricity
10 ωn Argument of perigee
11 Ω0-n Longitude of ascending node at the beginning of the week
11 I0-n Orbit inclination at toe
11 Ω.
Rate of Right ascension of ascending node (RAAN) difference from reference value*1
11 io-n-DOT Change rate in orbit inclination
11 Cis-n Amplitude of the sine harmonic correction term to the angle of inclination
11 Cic-n Amplitude of the cosine harmonic correction term to the angle of inclination
11 Crs-n Amplitude of the sine correction term to the orbit radius
11 Crc-n Amplitude of the cosine correction term to the orbit radius
11 Cus-n Amplitude of the sine harmonic correction term to the argument of latitude
11 Cuc-n Amplitude of the cosine harmonic correction term to the argument of latitude
* Relative to ]condcircles/se-semi[106.2 9REF (same value with GPS).
(1) Transmission Week Number
Bits 39 - 51 in message type 10 constitute a binary expression for the 8192 remainder of the current GPS Week Number. This is the same as in Section 30.3.3.1.1.1 of Applicable Document (1).
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(2) Signal health (L1/L2/L5)
The three single bits from bit 52 to bit 54 in message type 10 indicate the health of the L1, L2 and L5 signals, respectively, transmitted by the corresponding satellite. The value for the L1 signal is "1" in the event that there is a problem with one or more of the L1C/A, L1-SAIF or L1C signals. 0 No problems with signal 1 Problem with signal exists or signal cannot be used These bit indices are compared to the monitoring results at the present time for the corresponding satellite. The details are in accordance with Section 5.1.2.1.3. Health data are also present in message types 12, 31 and 37. The data in message type 10 are uploaded at a different time, so the data may differ from that for the transmission satellites of other messages and other satellite data.
(3) Data Predict Time of week: opt
Bits 55-65 in message type 10 indicate the data predict time of week ( opt ). The opt term provides the epoch time of week of the state estimate utilized for the prediction of satellite ephemeris parameters. This is the same as in Section 30.3.3.1.3 of Applicable Document (1).
(4) Accuracy indicator for Ephemeris data: oeURA index Bits 66-70 in message type 10 indicate the SIS accuracy indicator for Ephemeris data. For more information, see Section 5.1.2.1.3.2.
(5) Ephemeris data epoch: oet Bits 71 - 81 in message type 10 and bits 39 - 49 in message type 11 indicate the epoch for Ephemeris data. This is the same as in Figure 30-1 and Table 30-I of Applicable Document (1).
(6) Ephemeris data After the URAoe index in message type 10, the Ephemeris data (shown in Table 5.5.2-3) for the corresponding satellite are transmitted. In the data, ΔA represents the value of the Semi-Major Axis in the context of toe( oetA ) minus 42,164,200 [m]:
][200,164,42 mtAtA oeoe Other values are the same as in Figure 30-1 and Table 30-I of Applicable Document (1).
5.5.2.2.1.2 Characteristics of Ephemeris Data Parameters for Message Types 10 and 11
With the exception of those items shown in the previous section (5.5.2.2.1.1), the parameter characteristics for message types 10 and 11 (number of bits, LSB scale factor, data range and units) are the same as those shown in Table 30-I of Applicable Document (1). Bit allocation for message types 10 and 11 is the same as in Figures 30-1 and 30-2 of Applicable Document (1). However, Integrity Status Flag and L2C Phasing Flag were added in Figure 30-1 of Applicable Document (1), QZS-1 did not adopt. After "Phase Two", adoption of the Integrity Status flag is under study, but L2C Phasing Flag will not be adopted.
5.5.2.2.1.3 Message Types 10 and 11: User Algorithms for Satellite Positioning
In accordance with Section 6.3.5.
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5.5.2.2.2 Message types 30 through 35, 37, 46, 47, 49, 51 and 53: SV Clock Correction Parameters
5.5.2.2.2.1 Message types 30 through 35, 37, 46, 47, 49, 51 and 53: Content of SV Clock Parameters
Message types 30, 31, 32, 33, 34, 35 37, 46, 47, 49, 51 and 53 all contain SV clock parameters for the corresponding satellite such as those shown in Table 5.5.2-4. For an overview, see Section 30.3.3.2.1 of Applicable Document (1). Table 5.5.2-4 Definition of SV clock parameters for Navigational Message DL2C
Parameter Definition Difference from GPS definition
toc SV clock parameter epoch (seconds into week)
URAOC index SV clock accuracy index
URAOC1 index SV clock accuracy change index
URAOC2 index SV clock accuracy change rate index
af0-n SV clock bias correction term
af1-n SV clock drift correction term
af2-n SV clock drift rate correction term
(1) Data predict time of accuracy indicator for SV clock parameters (top)
Bits 39 - 49 indicate the data predict time of week (top) for the accuracy indicator for the SV clock parameters.
(2) SV clock parameter accuracy indicator (URAoc index) Bits 50 - 60 include the parameter needed to determine the SIS accuracy of the SV clock parameters (URAoc). Details are in accordance with Section 5.1.2.1.3.2.
(3) SV clock parameter epoch (toc) Bits 61 - 71 constitute the SV clock parameter epoch toc.
(4) SV clock parameter The SV clock parameter for the corresponding satellite, shown in Table 5.5.2-4, will be transmitted. The user algorithm is the same as in Section 20.3.3.3.3.1 of Applicable Document (1). However, certain parts of the definition are different; for more information, see Section 6.3.2.
5.5.2.2.2.2 Message types 30 through 35, 37, 46, 47, 49, 51 and 53: Characteristics of SV Clock Parameters
With the exception of those items shown in the previous section (Section 5.5.2.2.2.1), the parameter characteristics for message types 30, 31, 32, 33, 34, 35, 37, 46, 47, 49, 51 and 53 (clock correction parameter number of bits, LSB scale factor, data range and units) are the same as those shown in Table 30-III of Applicable Document (1).
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5.5.2.2.2.3 Message types 30 through 35, 37, 46, 47, 49, 51 and 53: User Algorithm for SV Clock
Correction Data
(1) Calculation of Accuracy for SV Clock Parameter: URAoc calculation. The algorithm used to determine the detailed user positioning accuracy (URAoc) expressed by URAoc index is the same as in Section 30.3.3.2.4 of Applicable Document (1). For more information about how to use URAoc, see Section 3.1.2.1.3. For more information about the content of URAoc, see Section 5.1.2.1.3. Note: Refer to the above Applicable Document (1), URAoc is calculated in quadratic
equation of the time. The coefficient of the linear term and that of quadratic term become larger than 0 by definition. The coefficient of the linear term would become larger than 1.7578 m after 3600 seconds from the top because top is updated every 3600 seconds for QZSS.
(2) Calculation of SV clock offset using SV clock parameters
As this is an estimate by the Control Segment by means of the L1C/A signal and the L2C signal code measurement, there are additions to the SV clock correction algorithm for one-signal users and 2-signal (L1C/A and L2C) users. See Section 6.3.2 for details.
5.5.2.2.3 Message Type 30, 46: Ionospheric Parameter and Group Delay Correction Parameter
In addition to the SV clock parameters (Section 5.5.2.2.2), message type 30 includes the ionospheric parameters like those shown in Table 5.5.2-5 and the internal signal group delay correction parameters shown in Table 5.5.2-6. For more information regarding the content of these parameters, see Section 30.3.3.3.1 of Applicable Document (1). Ionospheric parameters in Message type 46 are rebroadcast of parameters broadcasted by GPS. Since Group Delay Correction parameters broadcasted by GPS is NOT rebroadcasted by QZSS, bits 128 to 192 in message type 46 can NOT be used.
Table 5.5.2-5 Definition of ionospheric parameters for Navigational Message DL2C Parameter Definition Difference from GPS definition
α0 Ionospheric parameter α0 for Klobuchar model Coefficient optimized for Japan & environs
α1 Ionospheric parameter α1 for Klobuchar model Coefficient optimized for Japan & environs
α2 Ionospheric parameter α2 for Klobuchar model Coefficient optimized for Japan & environs
α3 Ionospheric parameter α3 for Klobuchar model Coefficient optimized for Japan & environs
β0 Ionospheric parameter β0 for Klobuchar model Coefficient optimized for Japan & environs
β1 Ionospheric parameter β1 for Klobuchar model Coefficient optimized for Japan & environs
β2 Ionospheric parameter β2 for Klobuchar model Coefficient optimized for Japan & environs
β3 Ionospheric parameter β3 for Klobuchar model Coefficient optimized for Japan & environs
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Table 5.5.2-6 Group Delay Correction Parameters (TGD, ISC) for Navigational Message DL2C Parameter Definition Difference from GPS definition
TGD LCQZSS.and.L1C/A group delay LCGPS and L1P(Y) group delay for GPS
ISCL1C/A N/A (Broadcasting value is 0.0) L1P(Y) - L1C/A for GPS
ISCL2C L1C/A – L2C group delay L1P(Y) – L2C for GPS
ISCL5I5 L1C/A - L5I5 group delay L1P(Y) – L5I5 for GPS
ISCI5Q5 L1C/A - L5Q5 group delay L1P(Y) – L5Q5 for GPS
LCQZSS: LCQZSS is the ionospheric error free linear combination of the L1C/A and L2C signals for QZSS
LCGPS: LCGPS is the ionospheric error free linear combination of the L1P(Y) and L2P(Y) signals for GPS
(1) Ionospheric parameters
This section provides the ionospheric parameters used by one-signal users (who use only the L1, L2 or L5 signal) when they use an ionospheric model to calculate the ionospheric delay. These parameters are specialized to fit the geographic area shown in Figure 4.1.5-1. User algorithms for one-signal users are in accordance with Sections 6.3.4 and 6.3.8. These parameters use data from the past 24 hours (Maximum) and are updated at least once per day except “ionospheric maximum periods”. The number of bits, scale factor, range and units are the same as in Section 20.3.3.5.2.5 and Table 20-X of Applicable Document (1).
(2) Estimating the L1-L2 group delay error Group delay error terms TGD, ISCL1C/A and ISCL2C for users of only one signal (L1C/A, L1C, L2C or L5) and L1/L2 users are contained in bits 128 - 166 of message type 30. Of these, ISCL1C/A has a value of zero. Table 30-IV of Applicable Document (1) shows the number of bits, scale factor, range and units. "Bit string "1000000000000" indicates that the group delay value cannot be used. The relevant algorithms are shown in Sections 6.3.3 and 6.3.4.
5.5.2.2.4 Message Types 31, 12, 37, 47, 28 and 53: Almanac Data
QZS Almanac data are provided by message types 31, 12 and 37. The Reduced Almanac is provided by message type 31 or 12, and the Midi Almanac is provided by message type 37. The PRN number for these message types indicates the last 6 bits of the QZS PRN. Almanac data for other satellite positioning systems are provided by message types 47, 28 and 53. The Reduced Almanac is provided by message type 47 or 28, and the Midi Almanac is provided by message type 53. Of the PRN numbers for these message types, numbers 1-32 are for GPS satellites. The Reduced Almanac for satellites is broadcast by a single satellite in a shorter interval than the Midi Almanac.
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Table 5.5.2-7 Definition of Midi Almanac parameters for Navigational Message DL2C Parameter Definition Difference from GPS definition
WNa-n GPS Week Number at the time of Midi Almanac generation
toa Midi Almanac epoch (second in week)
PRN no. When the message type number is 37, it indicates that this value is for a QZS satellite and constitutes the offset value from the PRN number of 193 for the target satellite. When the message type number is 53, it indicates that this value is the PRN value for a GPS satellite.
L1/L2/L5 Health L1, L2 and L5 signal health
E Eccentricity (offset from the nominal QZS eccentricity of 0.06)
Only values up to 0.03 can be expressed in the case of GPS
i Offset from the reference QZS orbit inclination (0.25 [semi-circles]) (Offset from 0.25 [semi-circle]=45 [deg])
In the case of GPS, the reference inclination is 0.3 [semi-circles], which represents 54 [deg].
Change rate in right ascension of ascending node (RAAN)
A Square root of Semi-Major Axis
0 Longitude of ascending node at the beginning of the week
Argument of perigee
M0 Mean anomaly
af0 Bias term for SV clock
af1 Drift term for SV clock
Table 5.5.2-8 Definition of Reduced Almanac parameters for Navigational Message DL2C Parameter Definition Difference from GPS definition
WNa-n GPS Week Number at the time of Reduced Almanac generation
toa Reduced Almanac epoch (second in week)
PRN no. When the message type number is 31 or 12, it indicates that this value is for a QZS satellite and constitutes the offset value from the PRN number of 193 for the target satellite. When the message type number is 47 or 28, it indicates that this value is the PRN value for a GPS satellite
δA Offset from the nominal QZS Semi-Major Axis of 42,164,200 [m]
In the case of GPS, indicates the offset from 26,559,710 [m]
Ω0 Longitude of ascending node at the beginning of the week
Φ0 Argument of latitude (= M0 + w) Based on the assumption that ω= 270 [deg]
L1/L2/L5 Health
L1, L2 and L5 signal health
(e) Implicit eccentricity (0.075 in the case of QZS) (precondition for above parameter)
0 in the case of GPS
(δi) Fixed at -0.0111 [semi-circles], the offset from the reference QZS orbit inclination of 0.25 [semi-circles] (precondition for above parameter)
In the case of GPS, fixed at +0.0056 [semi-circles], the offset from 0.3 [semi-circles]
(ω) Implicit Argument of Perigee (270 [deg] in QZS-1) (Precondition for above parameters)
0 [deg] in case of GPS
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5.5.2.2.4.1 Almanac Reference Week Number
Bits 39 - 51 in message types 12 and 28 and bits 128 - 140 in message types 31and 37 (and 47 and 53) indicate the Week Number (WNa-n) that serves as a reference for the Almanac reference time (toa) (see Section 20.3.3.5.2.2 of Applicable Document (1)). WNa-n is made up of 13 bits and is expressed by the modulo-8192 GPS Week Number (see Section 6.3.6) that serves as a reference for toa.
5.5.2.2.4.2 Almanac reference time
Bits 52-59 in message type 12 (and 28) and bits 141-148 in message types 31 and 37 (and also 47 and 53) indicate the Almanac reference time (toa).See Section 20.3.3.5.2.2 of Applicable Document (1).
5.5.2.2.4.3 Satellite PRN number
The first 6 bits in the 31-bit Reduced Almanac included in message types 31 and 12 (and also 47 and 28) constitute the corresponding satellite’s PRN. In the case of message types 31 and 12, the PRN constitutes the last 6 bits of the QZS PRN. In the case of message types 47 and 28, the PRN number 1 to 32 is a GPS PRN number. If the Almanac data is not effective, the value of the PRN Number is set to “111111” as in Applicable Document (3). In this event, the remainder of the rest of 22 bits in the data block shall be filler bits, i.e., alternating ones and zeros beginning with one, and the 3-Bit-Health is set to “111” (cf. Section 5.5.2.2.4.4). There is a PRN in bits 149-154 of the Midi Almanac included in message type 37 (and 53). In the case of message type 37, the PRN constitutes the last 6 bits of the QZS PRN. In the case of message type 53, the PRN is a GPS PRN.
5.5.2.2.4.4 Signal health (L1/L2/L5)
The three 1-Bit -Health indicators – bits 155, 156 and 157 in message type 37 (and 53) and bits 29, 30 and 31 in the Reduced Almanac in message types 31 and 12 (and also 47 and 28) relate to the L1, L2 and L5 signals for the satellite corresponding to the PRN number. Their meaning is covered in Section 5.1.2.1.3.
5.5.2.2.4.5 Midi Almanac data content
Message type 37 (and 53) provides the Almanac for the satellite with the PRN number shown in the message. The number of bits, scale factor, range and units are the same as in Table 30-V of Applicable Document (1). However, the QZS eccentricity and inclination differs from that of GPS and is provided relative to the reference values as noted below. (1) Eccentricity
(a) In the case of QZSS: nave0.06ae
(b) In the case of GPS: nave0.00 ae Reference in accordance with Applicable Document (1)
ae : Actual eccentricity value
nave : Eccentricity value included in navigation message
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(2) Inclination
(a) In the case of QZSS: ][25.0 circlesemiiia
(b) In the case of GPS: ][3.0 circlesemiiia Reference in accordance with Applicable Document (1) ia: Actual inclination value δi: Inclination value included in navigation message
For the user algorithm, see Section 6.3.6. The Midi Almanac data for the QZS are updated approximately once every 3.5 days. The velocity calculated by the Midi Almanac data is accurate within 30m/s.
5.5.2.2.4.6 Content of Reduced Almanac Data
Message type 31 and 12 (and also 47 and 28) contain multiple reduced Almanac data values. Semi major axis and inclination are provided relative to reference values as shown below. (1) Semi-Major Axis
(a) For QZSS: A[m] 42,164,200A
(b) For GPS: A[m] 26,559,710A Reference in accordance with Applicable Document (1)
(2) Eccentricity
(a) For QZSS: 0.075e
(b) For GPS: 0.0e Reference in accordance with Applicable Document (1)
(3) Orbit Angle of Elevation (a) For QZSS: [deg]43i
(b) For GPS: [deg]55i Reference in accordance with Applicable Document (1)
(4) Time change rate for right ascension of ascending node (RAAN)
(a) For QZSS: ]condscircles/sesemi[1078. 10
(b) For GPS: ]condscircles/sesemi[106.2 9 Reference in accordance with Applicable Document (1)
(5) Implicit Argument of Perigee
(a) For QZSS: [deg]270
(b) For GPS: [deg]0 The number of bits, LSB scale factor, range and units are the same as in Table 30-VI of Applicable Document (1). For the user algorithm, see Section 6.3.6. The Reduced Almanac data for the QZS are updated approximately every 3.5 days. The velocity calculated by the Reduced Almanac data is accurate within 350 m/s.
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5.5.2.2.5 Message type 32: Earth orientation parameter (EOP)
The Earth rotation parameter is included in message type 32. The definition, number of bits, scale factor, range, units, LSB, user algorithm, etc., for this parameter are all the same as table 30-VII in Applicable Document (1).
5.5.2.2.6 Message type 33, 49: UTC Parameters
The UTC parameters are included in message type 33 (and 49). When the Message Type = 33, the UTC parameters transmitted by the QZS is needed to link GPS time to UTC (NICT). When the Message Type = 49, those are gathered by receiving GPS signals at QZS Monitor Stations and re-broadcasted to link GPS time to UTC (USNO). The number of bits, scale factor, range, units, LSB, user algorithm, etc., for this parameter are all the same as Section 30.3.3.6 and Table 30-IX in Applicable Document (1).
5.5.2.2.7 Message Type 34, 13, 14: Differential Correction Data (DC Data)
Differential correction data (DC data) are included in message types 34, 13 and 14. These parameters provide users with correction terms for SV clock parameters and Ephemeris data transmitted by other satellites. DC data is divided into packets that comprise a 34-bit SV clock error correction (CDC) parameter and a 92-bit Ephemeris error correction (EDC) parameter. CDC and EDC data are paired, and users must use the CDC and EDC pair corresponding to the same Dopt and tOD. Message type 34 includes the CDC and EDC for one satellite. Message type 13 includes the CDC data for six satellites, while message type 14 includes the EDC data for two satellites. A DC Type indicator "0" indicates that the corresponding correction parameters should be applied to CNAV data, while "1" indicates that the corrections should be applied to the navigation message for the L1C/A signal. The content of the data packets is the same as Section 30.3.3.7 in Applicable Document (1). The content is shown in Table 5.5.2-9. The bit definition, number of bits, scale factor and unit for DC data are the same as Table 30-XI in Applicable Document (1). If the DC data is not effective, the value of the PRN Number is set to “11111111” as Section 30.3.3.7.2.3 in Applicable Document (1). In this case, DC type indicator is set to “0”.
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Table 5.5.2-9 Definition of parameters for DC data for Navigational Message DL2C Parameter Definition Difference from GPS definition
top-D Prediction time of week for DC data (second in week)
tOD Reference time of week for DC data (second in week)
DC Type indicator 1: For DLIC/A message 0: For DL2C message
PRN no. PRN no. (range 0 - 255) for satellite for which performance enhancement data will be applied 1 - 32 if target is GPS; 193 - 197 if target is QZSS
f0a Bias term for SV clock
f1a Drift correction term for SV clock
UDRA index User Differential Range Accuracy (UDRA) index
correction term for Ephemeris parameter
correction term for Ephemeris parameter
correction term for Ephemeris parameter
i Correction term for orbit inclination
Correction term for right ascension of ascending node (RAAN)
A Correction term for Semi-Major Axis
UD.
RA index UDRA rate index
5.5.2.2.7.1 Differential Correction (DC) data
DC data include the following. For more information regarding the use of DC data, see Section 3.1.2.1.3.4.
(1) Time of DC data estimation ( Dopt )
“ Dopt ” indicates the time (seconds into week) at which DC data were estimated. This value is the same as Section 30.3.3.7.2.1 in Applicable Document (1).
(2) DC data epoch ( ODt )
“ ODt ” indicates the epoch (seconds into week) for DC data. This value is the same as Section 30.3.3.7.2.2 in Applicable Document (1).
(3) Satellite PRN identification The 8-bit PRN specifies the satellite for which the corresponding DC data set is to be used. When PRN is 1-32, it indicates GPS; when PRN is 193-197, it indicates QZSS. If the bit values are all set to "1", then there are no DC data in the data block. This is the same as Section 30.3.3.7.2.3 in Applicable Document (1) in the sense that the remaining data consist of alternating bit values of "1" and "0".
(4) Use of CDC data Same as Section 30.3.3.7 in Applicable Document (1). For more information, see Section 6.3.9.2.
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(5) Use of EDC data
Same as Section 30.3.3.7 in Applicable Document (1). For more information, see Section 6.3.9.2.
5.5.2.2.7.2 DC Data Accuracy
The User Differential Range Accuracy, UDRAop-D, and its time derivative, UD.
RA, indicate the positioning accuracy after DC data have been applied to the SV clock parameter and Ephemeris data. The bit definition, number of bits, etc., and user algorithm are the same as Figure 30-16 and Section 30.3.3.7.5 in Applicable Document (1). For more information regarding the use of UDRAop-D and UD
.RA, see Section 3.1.2.1.3.5.
5.5.2.2.8 Message type 35, 51: GPS/GNSS time offset: GGTO
Message type 35 (and 51) is the parameter used to adjust GPS time to match other GNSS times. The bit definition, number of bits, scale factor (LSB), range and units are all the same as Figure 30-8 and Table 30-XI in Applicable Document (1). The effective period for GPS GNSS Time Offset (GGTO) is at least 24 hours.
Table 5.5.2-10 Definition of GPS GNSS Time Offset (GGTO) parameters for Navigational Message DL2C Parameter Definition Difference from GPS definition
tGGTO Seconds into GGTO reference week
WNGGTO GGTO reference Week Number
GNSS ID See Section 5.5.2.2.8.1
A0GGTO GPST bias term associated with other GNSS system time
A1GGTO GPST drift term associated with other GNSS system time
A2GGTO GPST drift rate term associated with other GNSS system time
5.5.2.2.8.1 GNSS - ID
Bits 155-157 in message type 35 define the other satellite positioning systems to which data offsets with respect to GPS are applied. The definitions of these three bits are as follows.
000: Data cannot be used
001: Galileo
010: GLONASS
011: QZSS
100 - 111: Spare
5.5.2.2.8.2 GPS/GNSS Time Offset
The algorithm used to determine GPS GNSS Time Offset (GGTO) is the same as in Applicable Document (1). However, the QZS SV clock parameter already uses GPST as the reference, so the time offset value for GPS and QZSS (GQTO) is zero.
5.5.2.2.9 Message Types 15: Text Messages
Text messages are transmitted using the 29 8-bit ASCII characters in message type 15. The bit definition, number of bits, etc., is the same as Figure 30-14 in Applicable Document (1).
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5.6 L5 signal
5.6.1 RF characteristics
5.6.1.1 Signal configuration
In accordance with Section 5.1.
Inner FEC½ Coder
(7 Convolution)
10-symbol
NH Code(1ksps)
Outer FECCoder(CRC 24)
CNAV(100sps)
L5I
L5
Navigation
Message(276bits)
300bits/6s 600bits/6s
10bits-Length/10ms
20-symbol
NH Code(1ksps)
20bits-Length/20ms
L5Q
PRN
as Ranging CodeRanging Code
(10.23Mcps)
10230chips-Length/1ms
XI
XQ
Figure 5.6.1-1 L5 Signal Structure
5.6.1.2 Carrier wave properties
In accordance with Section 5.1.
5.6.1.3 Code properties
5.6.1.3.1 Code attributes
Same as sections 3.2.1, 3.3.2 and 6.3.4 of Applicable Document (2). However, the PRN code number is as described in Section 5.1.1.11.1 of this document.
5.6.1.3.2 Non-standard code
In the event of a problem with QZSS, a non-standard code (NSC) is transmitted. This is done to protect users by ensuring that they do not receive or use erroneous navigation data.
5.6.2 Message
5.6.2.1 Message configuration
Each message of the L5 signal (DL5) comprises 300 bits: 276 bits of data and 24 parity check bits. Each message is broadcast for 6 seconds. This message configuration is the same as Section 20.3.2 in Applicable Document (2).
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5.6.2.1.1 Preamble
The 8-bit preamble added to the beginning of each frame is the same as Section 20.3.3 in Applicable Document (2).
5.6.2.1.2 PRN number
The 6-bit PRN number added after the preamble in each frame is the last 6 bits of the PRN number for the QZS transmitting the corresponding message.
5.6.2.1.3 Message type ID
The 6-bit message type ID added after the PRN number in each frame signifies the data contained in that frame. Table 5.6.2-1 specifies the message content for each of the individual message types. For more information, see Section 5.6.2.2. The different types of messages are transmitted at intervals not to exceed the Maximum Broadcast Periods specified in Table 5.6.2-2. QZSs may transmit the same message type with different timing.
Table 5.6.2-1 Definitions of message types for Navigational Message DL5 Message type Message content Notes
10 Health, URA, Ephemeris 1
11 Ephemeris 2
30, 46 SV clock, ionospheric parameter, ISC
When value is 46: Rebroadcast of ionospheric parameters broadcasted by GPS, however ISC broadcasted by GPS is not rebroadcasted by QZSS
31, 47* SV clock, Reduced Almanac When value is 47: Rebroadcast of GPS reduced Almanac
32 SV clock, EOP (Earth Orientation Parameter)
33, 49 SV clock, UTC parameter When value is 49: Rebroadcast of GPS UTC parameters
34 SV clock, performance enhancement data Transmitted as needed
35, 51 SV clock, GGTO (GPS GNSS Time Offset ) When value is 51: Rebroadcast of GGTO broadcasted by GPS
37, 53 SV clock, Midi Almanac When value is 53: Rebroadcast of GPS Midi Almanac
12*, 28 Reduced Almanac When value is 28: Rebroadcast of GPS reduced Almanac
13 SV clock performance enhancement data Transmitted as needed
14 Ephemeris performance enhancement data Transmitted as needed
15 Text Transmitted as needed * QZS-1 does not be broadcasting the data of Type 12 and 47 because the contents of them are same with those of type 31 and 28. Broadcasting the data of type 12 and 47 after "Phase Two" is under study
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Table 5.6.2-2 Maximum Transmit periods for Navigational Message DL5
Message Data Message Type Maximum broadcast Period
Notes
Ephemeris 10,11 24 seconds
SV clock 30-35, 37, 46, 47, 49, 51, 53
24 seconds
ISC, ionospheric parameter 30 144 seconds ISC, ionospheric parameter (GPS rebroadcasting)
46 *
Reduced Almanac of QZSS 31 or 12 10 minutes All necessary SV data must be transmitted
Reduced Almanac of GPS (GPS rebroadcasting)
47 or 28 * All necessary SV data must be transmitted
Midi Almanac of QZSS 37 60 minutes All necessary SV data must be transmitted
Midi Almanac of GPS (GPS rebroadcasting)
53 * All necessary SV data must be transmitted
EOP 32 15 minutes
UTC parameters 33 144 seconds
UTC parameters (GPS rebroadcasting) 49 *
DC data 34 or 13 & 14 15 minutes (*) Only when performance enhancement data are effective
GGTO (GPS-QZSS Time Offset) 35 144 seconds
GGTO (GPS-Galileo Time Offset) 51 *
Text 15 As needed * We will not define the maximum transmit period for GPS rebroadcasting parameters and GPS DC data.
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5.6.2.1.4 TOW count
The 17-bit TOW (Time of Week) count that follows the message type ID in each frame indicates the time at the beginning of the next frame, which is six times that value. This is the same as Section 20.3.3 in Applicable Document (2).
5.6.2.1.5 "Alert" flag
The 1-bit "Alert" flag that follows the TOW count in each frame is in accordance with Section 5.1.2.1.3.
5.6.2.1.6 FEC and parity algorithm
The CNAV will be encoded with FEC. The algorithm for encoding is the same as in Section 3.3.3.1.1 of Applicable Document (2). The 24-bit parity code added after the 300-bit frame. The parity algorithm is the same as in Section 20.3.5 of Applicable Document (2).
5.6.2.2 Message content
With the exception of the list in Section 8.1.2, the content of the message is the same as in Applicable Document (2). 5.6.2.2.1 Ephemeris data and health for message types 10 and 11
5.6.2.2.1.1 Content of Ephemeris data and health for message types 10 and 11
Message types 10 and 11 include the Ephemeris data (such as that shown in Table 5.6.2-3) for the corresponding satellite. The general content is the same as Section 20.3.3.1 in Applicable Document (2).
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Table 5.6.2-3 Definition of Ephemeris parameters for Navigational Message D L5
Parameter Definition Difference from GPS definition
10 WNn GPS Week Number
10 L1/L2/L5 Health L1, L2 and L5 signal health
10 top Data predict time of week (seconds into week)
10 URAoe index Ephemeris accuracy index
10 11
toe Ephemeris epoch (seconds into week)
10 A Difference from semi major axis at toe In the case of QZS, indicates difference with 42,164,200 [m]
In the case of GPS, indicates difference with 26,559,710 [m]
10 A Change rate in semi major axis
10 n0 Difference from mean motion calculation at toe
10 0n Change rate from mean motion calculation
10 M0-n Mean anomaly at toe
10 en Eccentricity
10 ωn Argument of perigee
11 Ω0-n Longitude of ascending node at the beginning of the week
11 i0-n Orbit inclination in toe
11 Ω.
Rate of Right ascension of ascending node (RAAN) difference from reference value*
11 io-n-DOT Change rate in orbit inclination
11 Cis-n Amplitude of the sine harmonic correction term to the angle of inclination
11 Cic-n Amplitude of the cosine harmonic correction term to the angle of inclination
11 Crs-n Amplitude of the sine correction term to the orbit radius
11 Crc-n Amplitude of the cosine correction term to the orbit radius
11 Cus-n Amplitude of the sine harmonic correction term to the argument of latitude
11 Cuc-n Amplitude of the cosine harmonic correction term to the argument of latitude
* Relative to ]condcircles/se-semi[106.2 9REF (same value with GPS)
(1) Transmission Week Number
Bits 39 - 51 in message type 10 constitute a binary expression for the 8192 remainder of the current GPS Week Number. This is the same as Section 20.3.3.1.1.1 in Applicable Document (2).
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(2) Signal health (L1/L2/L5)
The three single bits from bit 52 to bit 54 in message type 10 indicate the health of the L1, L2 and L5 signals, respectively, transmitted by the corresponding satellite. The value for the L1 signal is "1" in the event that there is a problem with one or more of the L1C/A, L1-SAIF or L1C signals. 0 No problems with signal 1 Problem with signal exists or signal cannot be used These bit indices are compared to the monitoring results at the present time for the corresponding satellite. The details are in accordance with Section 5.1.2.1.3. Health data are also present in message types 12, 31 and 37. The data in message type 10 are uploaded at a different time, so the data may differ from that for the transmission satellites of other messages and other satellite data.
(3) Data Predict Time of week: opt
Bits 55-65 in message type 10 indicate the data predict time of week ( opt ). The opt term provides the epoch time of week of the state estimate utilized for the prediction of satellite ephemeris parameters. This is the same as in Section 20.3.3.1.1.3 of Applicable Document (2).
(4) Accuracy indicator for Ephemeris data: oeURA index Bits 66-70 in message type 10 indicate the SIS accuracy indicator for Ephemeris data. For more information, see Section 5.1.2.1.3.2.
(5) Ephemeris data epoch: oet Bits 71 - 81 in message type 10 and bits 39 - 49 in message type 11 indicate the epoch for Ephemeris data. This is the same as Table 20-I in Applicable Document (2).
(6) Ephemeris data After the URAoe index in message type 10, the Ephemeris data (shown in Table 5.6.2-3) for the corresponding satellite are transmitted. In the data, ΔA represents the value of the Semi-Major Axis in the context of toe, oetA , minus 42,164,200 [m]:
][200,164,42 mtAtA oeoe Other values are the same as Table 20-I in Applicable Document (2).
5.6.2.2.1.2 Characteristics of Ephemeris Data Parameters for Message Types 10 and 11
With the exception of those items shown in the previous section (Section 5.6.2.2.1.1), the parameter characteristics for message types 10 and 11 (number of bits, LSB scale factor, data range and units) are the same as Table 20-I in Applicable Document (2). Bit allocation for message types 10 and 11 is the same as Figure 20-1 and 20-2 in Applicable Document (2). However, Integrity Status Flag and L2C Phasing Flag were added in Figure 20-1 of Applicable Document (2), QZS-1 did not adopt. After "Phase Two", adoption of the Integrity Status flag is under study, but L2C Phasing Flag will not be adopted.
5.6.2.2.1.3 Message Types 10 and 11: User Algorithms for Satellite Positioning
In accordance with Section 6.3.5.
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5.6.2.2.2 Message types 30 through 35, 37, 46, 47, 49, 51 and 53: SV Clock Correction Parameters
5.6.2.2.2.1 Message types 30 through 35, 37, 46, 47, 49, 51 and 53: Content of SV Clock Parameters
Message types 30, 31, 32, 33, 34, 35, 37, 46, 47, 49, 51 and 53 all contain SV clock parameters for the corresponding satellite such as those shown in Table 5.6.2-4. For an overview, see Section 20.3.3.2 in Applicable Document (2). Table 5.6.2-4 Definition of SV clock parameters for Navigational Message D L5
Parameter Definition Difference from GPS definition
toc SV clock parameter epoch (seconds into week)
URAOC index SV clock accuracy index
URAOC1 index SV clock accuracy change index
URAOC2 index SV clock accuracy change rate index
af0-n SV clock bias correction term
af1-n SV clock drift correction term
af2-n SV clock drift rate correction term
(1) Data predict time of accuracy indicator for SV clock parameters (top) Bits 39 - 49 indicate the data predict time of week (top) for the accuracy indicator for the SV clock parameters.
(2) SV clock parameter accuracy indicator (URAoc index) Bits 50 - 60 include the parameter needed to determine the SIS accuracy of the SV clock parameters (URAoc). Details are in accordance with Section 5.1.2.1.3.2.
(3) SV clock parameter epoch (toc) Bits 61 - 71 constitute the SV clock parameter epoch toc.
(4) SV clock parameter The SV clock parameter for the corresponding satellite, shown in Table 5.6.2-4, will be transmitted. The user algorithm is the same as Section 20.3.3.2.4 in Applicable Document (2). However, certain parts of the definition are different; for more information, see Section 6.3.2.
5.6.2.2.2.2 Message types 30 through 35, 37, 46, 47, 49, 51 and 53: Characteristics of SV Clock Parameters
With the exception of those items shown in the previous section (Section 5.6.2.2.2.1), the parameter characteristics for message types 30, 31, 32, 33, 34, 35, 37, 46, 47, 49, 51 and 53 (clock correction parameter number of bits, LSB scale factor, data range and units) are the same as those shown in Applicable Document (2) (Table 20-III).
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5.6.2.2.2.3 Message types 30 through 35, 37, 46, 47, 49, 51 and 53: User Algorithm for SV Clock
Correction Data
(1) Calculation of Accuracy for SV Clock Parameter: URAoc calculation. The algorithm used to determine the detailed user positioning accuracy (URAoc) expressed by URAoc index is the same as Section 20.3.3.2.4 in Applicable Document (2). For more information about how to use URAoc, see Section 3.1.2.1.3. For more information about the content of URAoc, see Section 5.1.2.1.3. Note: Refer to the above Applicable Document (2), URAoc is calculated in quadratic
equation of the time. The coefficient of the linear term and that of quadratic term become larger than 0 by definition. The value of the linear term would become larger than 1.7578 m after 3600 seconds from the top because top is updated every 3600 seconds for QZSS.
(2) Calculation of SV clock offset using SV clock parameters
As this is an estimate by the Control Segment by means of the L1C/A signal and the L2C signal code measurement, there are additions to the SV clock correction algorithm for one-signal users and 2-signal (L1C/A and L2C) users. See Section 6.3.2 for details.
5.6.2.2.3 Message Type 30, 46: Ionospheric Parameter and Group Delay Correction Parameter
In addition to the SV clock parameters (Section 5.6.2.2.2), message type 30 includes the ionospheric parameters like those shown in Table 5.6.2-5 and the internal signal group delay correction parameters shown in Table 5.6.2-6. For more information regarding the content of these parameters, see Section 20.3.3.3 in Applicable Document (2).
Ionospheric parameters in Message type 46 are rebroadcast of parameters broadcasted by GPS. Since Group Delay Correction parameters broadcasted by GPS is NOT rebroadcasted by QZSS, bits 128 to 192 in message type 46 can NOT be used.
Table 5.6.2-5 Definition of ionospheric parameters for Navigational Message D L5 Parameter Definition Difference from GPS definition
α0 Ionospheric parameter α0 for Klobuchar model Coefficient optimized for Japan & environs
α1 Ionospheric parameter α1 for Klobuchar model Coefficient optimized for Japan & environs
α2 Ionospheric parameter α2 for Klobuchar model Coefficient optimized for Japan & environs
α3 Ionospheric parameter α3 for Klobuchar model Coefficient optimized for Japan & environs
β0 Ionospheric parameter β0 for Klobuchar model Coefficient optimized for Japan & environs
β1 Ionospheric parameter β1 for Klobuchar model Coefficient optimized for Japan & environs
β2 Ionospheric parameter β2 for Klobuchar model Coefficient optimized for Japan & environs
β3 Ionospheric parameter β3 for Klobuchar model Coefficient optimized for Japan & environs
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Table 5.6.2-6 Group Delay Correction Parameters (TGD, ISC) for Navigational Message D L5 Parameter Definition Difference from GPS definition
TGD LCQZSS and L1C/A group delay LCGPS and L1P(Y) group delay for GPS
ISCL1C/A N/A (Broadcasting value is 0.0) L1P(Y) - L1C/A for GPS
ISCL2C L1C/A – L2C group delay L1P(Y) – L2C for GPS
ISCL5I5 L1C/A - L5I5 group delay L1P(Y) – L5I5 for GPS
ISCI5Q5 L1C/A - L5Q5 group delay L1P(Y) – L5Q5 for GPS
LCQZSS: LCQZSS is the ionospheric error free linear combination of the L1C/A and L2C signals for QZSS
LCGPS: LCGPS is the ionospheric error free linear combination of the L1P(Y) and L2P(Y) signals for GPS
(1) Ionospheric parameters This section provides the ionospheric parameters used by one-signal users (who use only the L1, L2 or L5 signal) when they use an ionospheric model to calculate the ionospheric delay. These parameters are specialized to fit the geographic area shown in Figure 4.1.5-1. User algorithms for one-signal users are in accordance with Sections 6.3.4 and 6.3.8. These parameters use data from the past 24 hours (Maximum) and are updated at least once per day except “ionospheric maximum periods”. The number of bits, scale factor, ranges and units are the same as Table 20-IV in Applicable Document (2).
(2) Estimating the L1-L5 group delay error Group delay error terms TGD, ISCL5I5 and ISCL5Q5 for users of only one signal (L5) and L1/L5 users are contained in bits 128-140, 167-192 of message type 30. Table 20-IV in Applicable Document (2) shows the number of bits, scale factor, range and units. "Bit string "1000000000000" indicates that the group delay value cannot be used. The relevant algorithms are shown in Sections 6.3.3 and 6.3.4.
5.6.2.2.4 Message Types 31, 12, 37, 47, 28 and 53: Almanac Data
QZS Almanac data are provided by message types 31, 12 and 37. The Reduced Almanac is provided by message type 31 or 12, and the Midi Almanac is provided by message type 37. The PRN number for these message types indicates the last 6 bits of the QZS PRN. Almanac data for other satellite positioning systems are provided by message types 47, 28 and 53. The Reduced Almanac is provided by message type 47 or 28, and the Midi Almanac is provided by message type 53. Of the PRN numbers for these message types, numbers 1-32 are for GPS satellites. The Reduced Almanac for satellites is broadcast by a single satellite in a shorter interval than the Midi Almanac.
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Table 5.6.2-7 Definition of Midi Almanac parameters for Navigational Message DL5 Parameter Definition Difference from GPS definition
WNa-n GPS Week Number at the time of Midi Almanac generation
toa Midi Almanac epoch (second in week)
PRN no. When the message type number is 37, it indicates that this value is for a QZS satellite and constitutes the offset value from the PRN number of 193 for the target satellite. When the message type number is53, it indicates that this value is the PRN value for a GPS satellite.
L1/L2/L5 Health L1, L2 and L5 signal health
E Eccentricity (offset from the nominal QZS eccentricity of 0.06)
Only values up to 0.03 can be expressed in the case of GPS
i Offset from the reference QZS orbit inclination (0.25 [semi-circles]) (Offset from 0.25 [semi-circles]=45 [deg])
In the case of GPS, the reference inclination is 0.3 [semi-circles], which represents 54 [deg].
Change rate in right ascension of ascending node (RAAN)
A Square root of Semi-Major Axis
0 Longitude of ascending node at the beginning of the week
Argument of perigee
M0 Mean anomaly
af0 Bias term for SV clock
af1 Drift term for SV clock
Table 5.6.2-8 Definition of Reduced Almanac parameters for Navigational Message DL5 Parameter Definition Difference from GPS definition
WNa-n GPS Week Number at the time of Reduced Almanac generation
toa Reduced Almanac epoch (second in week)
PRN no. When the message type number is 31 or 12, it indicates that this value is for a QZS satellite and constitutes the offset value from the PRN number of 193 for the target satellite. When the message type number is 47 or 28, it indicates that this value is the PRN value for a GPS satellite
δA Offset from the nominal QZS Semi-Major Axis of 42,164,200 [m]
In the case of GPS, indicates the offset from 26,559,710 [m]
Ω0 Longitude of ascending node at the beginning of the week
Φ0 Argument of latitude (= M0 + w) Based on the assumption that ω= 270 [deg]
L1/L2/L5
Health
L1, L2 and L5 signal health
(e) Implicit eccentricity (0.075 in the case of QZS) (precondition for above parameter)
0 in the case of GPS
(δi) Fixed at -0.0111 [semi-circles], the offset from the reference QZS orbit inclination of 0.25 [semi-circles] (precondition for above parameter)
In the case of GPS, fixed at +0.0056 [semi-circles], the offset from 0.3 [semi-circles]
(ω) Implicit Argument of Perigee (270 [deg] in QZS-1 )
(Precondition for above parameters) 0 [deg] in case of GPS
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5.6.2.2.4.1 Almanac Reference Week Number
Bits 39 - 51 in message types 12 and 28 and bits 128 - 140 in message types 31 and 37 (and 47 and 53) indicate the Week Number (WNa-n) that serves as a reference for the Almanac reference time (toa). WNa-n is made up of 13 bits and is expressed by the modulo-8192 GPS Week Number (see Section 6.3.6) that serves as a reference for toa.
5.6.2.2.4.2 Almanac reference time
Bits 52-59 in message type 12 (and 28) and bits 141-148 in message types 31 and 37 (and also 47 and 53) indicate the Almanac reference time (toa).
5.6.2.2.4.3 Satellite PRN number
The first 6 bits in the 31-bit Reduced Almanac included in message types 31 and 12 (and also 47 and 28) constitute the corresponding satellite’s PRN. In the case of message types 31 and 12, the PRN constitutes the last 6 bits of the QZS PRN. In the case of message types 47 and 28, the PRN is a GPS PRN. There is a PRN in bits 149-154 of the Midi Almanac included in message type 37 (and 53). In the case of message type 37, the PRN constitutes the last 6 bits of the QZS PRN. In the case of message type 53, the PRN number 1 to 32 is a GPS PRN number. If the Almanac data is not effective, the value of the PRN Number is set to “111111” as in Applicable Document (3). In this event, the remainder of the rest of 22 bits in the data block shall be filler bits, i.e., alternating ones and zeros beginning with one, and the 3-Bit-Health is set to “111” (cf. Section 5.5.2.2.4.4).
5.6.2.2.4.4 Signal health (L1/L2/L5)
The three 1-Bit Health indicators – bits 155, 156 and 157 in message type 37 (and 53) and bits 29, 30 and 31 in the Reduced Almanac in message types 31 and 12 (and 28) relate to the L1, L2 and L5 signals for the satellite corresponding to the PRN number. Their meaning is covered in Section 5.1.2.1.3.
5.6.2.2.4.5 Midi Almanac data content
Message type 37 (and 53) provides the Almanac for the satellite with the PRN number shown in the message. The number of bits, scale factor, ranges and units are the same as Table 20-V in Applicable Document (2). However, the QZS eccentricity and inclination differs from that of GPS and is provided relative to the reference values as noted below. (1) Eccentricity
(a) In the case of QZSS: nave0.06ae
(b) In the case of GPS: nave0.00 ae Reference in accordance with Applicable Document (2)
ae : Actual eccentricity value
nave : Eccentricity value included in navigation message
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(2) Inclination
(a) In the case of QZSS: ][25.0 circlesemiiia
(b) In the case of GPS: ][3.0 circlesemiiia Reference in accordance with Applicable Document (2) ia: Actual inclination value
i : Inclination value included in navigation message For the user algorithm, see Section 6.3.6. The Midi Almanac for the QZS data is updated approximately once every 3.5 days. The velocity calculated by the Midi Almanac data is accurate within 30m/s.
5.6.2.2.4.6 Content of Reduced Almanac Data
Message type 31 and 12 (and also 47 and 28) contain multiple reduced Almanac data values. Reduced Almanac data values are provided relative to reference values as shown below. (1) Semi-Major Axis
(a) For QZSS: A[m] 42,164,200A
(b) For GPS: A[m] 26,559,710A Reference in accordance with Applicable Document (2)
(2) Eccentricity
(a) For QZSS: 0.075e
(b) For GPS: 0.0e Reference in accordance with Applicable Document (2)
(3) Orbit Angle of Elevation (a) For QZSS: [deg]43i
(b) For GPS: [deg]55i Reference in accordance with Applicable Document (2)
(4) Time change rate for right ascension of ascending node (RAAN)
(a) For QZSS: ]condscircles/sesemi[1078. 10
(b) For GPS: ]condscircles/sesemi[106.2 9 Reference in accordance with Applicable Document (2)
(5) Implicit Argument of Perigee
(a) For QZSS: [deg]270
(b) For GPS: [deg]0 The number of bits, LSB scale factor, ranges and units are the same as Table 20-VI in Applicable Document (2). For the user algorithm, see Section 6.3.6. The Reduced Almanac data for the QZS are updated approximately every 3.5 days. The velocity calculated by the Reduced Almanac data is accurate within 350 m/s.
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5.6.2.2.5 Message type 32: Earth Orientation Parameter (EOP)
The Earth Orientation Parameter is included in message type 32. The definition, number of bits, scale factor, range, units, LSB, user algorithm, etc., for this parameter are all the same as Section 20.3.3.5 in Applicable Document (2).
5.6.2.2.6 Message type 33, 49: UTC Parameters
The UTC parameters are included in message type 33 (and 49). When the Message Type = 33, the UTC parameters transmitted by the QZS is needed to link GPS time to UTC (NICT). When the Message Type = 49, those are gathered by receiving GPS signals at QZS Monitor Stations and re-broadcasted to link GPS time to UTC (USNO). The number of bits, scale factor, range, units, LSB, user algorithm, etc., for this parameter are all the same as Section 20.3.3.6 in Applicable Document (2).
5.6.2.2.7 Message Type 34, 13, 14: Differential Correction Data (DC Data)
Differential correction data (DC data) are included in message types 34, 13 and 14. These parameters provide users with correction terms for SV clock parameters and Ephemeris data transmitted by other satellites. DC data is divided into packets that comprise a 34-bit SV clock error correction (CDC) parameter and a 92-bit Ephemeris error correction (EDC) parameter. CDC and EDC data are paired, and users must use the CDC and EDC pair corresponding to the same top-D and tOD. Message type 34 includes the CDC and EDC for one satellite. Message type 13 includes the CDC data for six satellites, while message type 14 includes the EDC data for two satellites. A DC Type indicator "0" indicates that the corresponding correction parameters should be applied to CNAV data, while "1" indicates that the corrections should be applied to the navigation message for the L1C/A signal. The content of the data packets is the same as Section 20.3.3.7 in Applicable Document (2). The content is shown in Table 5.6.2-9. The bit definition, number of bits, scale factor and unit for DC data are the same as Figure 20-17 and Table 20-X in Applicable Document (2). If the DC data is not effective, the value of the PRN Number is set to “11111111” as Section 20.3.3.7.2.3 in Applicable Document (2). In this case, DC type indicator is set to “0”.
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Table 5.6.2-9 Definition of parameters for DC data for Navigational Message DL5 Parameter Definition Difference from GPS definition
top-D Prediction time of week for DC data (seconds in week)
tOD Reference time of week for DC data (seconds in week)
DC Type Indicator 1: For DLIC/A message 0: For DL5 message
PRN no. PRN no. (range 0 - 255) for satellite for which DC data will be applied 1 - 32 if GPS; 193 – 202 if QZSS
f0a Bias term for SV clock
f1a Drift correction term for SV clock
UDRA index User Differential Range Accuracy (UDRA) index
correction term for Ephemeris parameter
correction term for Ephemeris parameter
correction term for Ephemeris parameter
i Correction term for orbit inclination
Correction term for right ascension of ascending node (RAAN)
A Correction term for Semi-Major Axis
UD.
RA index UDRA rate index
5.6.2.2.7.1 Differential Correction (DC) data
DC data include the following. For more information regarding the use of DC data, see Section 3.1.2.1.3.4.
(1) Time of DC data estimation ( Dopt )
“ Dopt ” indicates the time (seconds into week) at which DC data were estimated. This value is the same as Section 20.3.3.7.2.1 in Applicable Document (2).
(2) DC data epoch ( ODt )
“ ODt ” indicates the epoch (seconds into week) for DC data. This value is the same as Section 20.3.3.7.2.2 in Applicable Document (2).
(3) Satellite PRN identification The 8-bit PRN specifies the satellite for which the corresponding DC data set is to be used. When PRN is 1-32, it indicates GPS; when PRN is 193-197, it indicates QZSS. If the bit values are all set to "1", then there are no DC data in the data block. This is the same as Section 20.3.3.7.2.3 in Applicable Document (2) in the sense that the remaining data consist of alternating bit values of "1" and "0".
(4) Use of CDC data Same as Section 20.3.3.7 in Applicable Document (2). For more information, see Section 6.3.9.2.
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(5) Use of EDC data Same as Section 20.3.3.7 in Applicable Document (2). For more information, see Section 6.3.9.2.
5.6.2.2.7.2 DC Data Accuracy
The User Differential Range Accuracy, UDRAop-D, and its time derivative, UD.
RA, indicate the positioning accuracy after DC data have been applied to the SV clock parameter and Ephemeris data. The bit definition, number of bits, etc., and user algorithm are the same as Section 20.3.3.7.5 in Applicable Document (2). For more information regarding the use of UDRAop-D and UD
.RA, see Section 3.1.2.1.3.5.
5.6.2.2.8 Message type 35, 51: GPS/GNSS time offset: GGTO
Message type 35 (and 51) is the parameter used to adjust GPS time to match other GNSS times. The bit definition, number of bits, scale factor (LSB), range and units are all the same as Table 02-XI in Applicable Document (2). The effective period for GPS GNSS Time Offset (GGTO) is at least 24 hours.
Table 5.6.2-10 Definition of GPS GNSS Time Offset (GGTO) parameters for Navigational Message DL5 Parameter Definition Difference from GPS definition
tGGTO Seconds into GGTO reference week
WNGGTO GGTO reference Week Number
GNSS ID See Section 5.6.2.2.8.1
A0GGTO GPST bias term associated with the other GNSS
A1GGTO GPST drift term associated with the other GNSS
A2GGTO GPST drift rate term associated with the other GNSS
5.6.2.2.8.1 GNSS - ID
Bits 155-157 in message type 35 define the other satellite positioning systems to which data offsets with respect to GPS are applied. The definitions of these three bits are as follows. 000 Data cannot be used 001 Galileo 010 GLONASS 011 QZSS 100 - 111 Spare
5.6.2.2.8.2 GPS/GNSS Time Offset
The algorithm used to determine GPS GNSS Time Offset (GGTO) is the same as Section 20.3.3.8 in Applicable Document (2). However, the QZS SV clock parameter already uses GPST as the reference, so the time offset value for GPS and QZSS (GQTO) is zero.
5.6.2.2.9 Message Types 15: Text Messages
Text messages are transmitted using the 29 8-bit ASCII characters in message type 15. The bit definition, number of bits, etc., is the same as Figure 20-14 in Applicable Document (2).
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5.7 LEX signal
5.7.1 RF Signal Characteristics
5.7.1.1 Signal Configuration
The LEX signal is modulated by BPSK (5), as specified in Section 5.1. As shown in Figure 5.7.1-1, the LEX baseband signal, CLEX, is generated with a chipping rate of 5.115 MChip/s by interleaving the following two 2.5575 Mcps bit streams: (a) a 4ms PRN Short Code modulated by means of code shift keying (CSK) by the Reed-Solomon encoded Navigation message, and (b) a 410 ms PRN Long Code modulated by squarewave with a period of 820 ms beginning from 0 ("010101..."). As defined in Figure 5.7.1-1, CSK modulation shifts the phase of the PRN code by the number of chips indicated by the 8-bit encoded Navigational message symbol.
Nav Message8bits/Symbol
Reed-Solomon(255,223)Coding
CSK Modulator (*)
Long Code (410ms) : 2.5575MChip/s
Short Code (4ms) : 2.5575MChip/s
1744 Bits/s 250 Symbols/s (2000 Bits/s)
2.5575MChip/s
Clock 5.115MHz
MSB
PRN(1) PRN(10230)
PRN(N+1) PRN(10230) PRN(1) PRN(N -1) PRN(N)
8 Bits (1Symbol) Value = N (as Decimal:N=0 - 255)
Nav Message Data
Original PRN Code Pattern
CSK Modulated PRN Code Pattern by “N” value
LSB
4 ms
Code Phase Shift by CSK Modulation
Time
(*) Definition of Code shift Keying (CSK) Modulation
LEXC5.115 MChip/s
Ranging Code
Generator
Squarewavewhich starts from “0”
ie. “010101…”
820ms period
2.5575MChip/s
Nav Message8bits/Symbol
Reed-Solomon(255,223)Coding
CSK Modulator (*)
Long Code (410ms) : 2.5575MChip/s
Short Code (4ms) : 2.5575MChip/s
1744 Bits/s 250 Symbols/s (2000 Bits/s)
2.5575MChip/s
Clock 5.115MHz
MSB
PRN(1) PRN(10230)
PRN(N+1) PRN(10230) PRN(1) PRN(N -1) PRN(N)
8 Bits (1Symbol) Value = N (as Decimal:N=0 - 255)
Nav Message Data
Original PRN Code Pattern
CSK Modulated PRN Code Pattern by “N” value
LSB
4 ms
Code Phase Shift by CSK Modulation
Time
(*) Definition of Code shift Keying (CSK) Modulation
LEXCLEXC5.115 MChip/s
Ranging Code
Generator
Squarewavewhich starts from “0”
ie. “010101…”
820ms period
2.5575MChip/s
Figure 5.7.1-1 LEX Signal Structure
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5.7.1.2 Carrier Wave Properties
In accordance with Section 5.1.
5.7.1.3 Code Properties
5.7.1.3.1 Overview of LEX Code
As shown in Figure 5.7.1-2, the LEX signal code comprises a Kasami series Short Code (2.5575 MChip/s) with a chip length of 10,230 and a 4 ms period, and a Kasami series Long Code (2.5575 MChip/s) with a chip length of 1,048,575 and a 410 ms period.
I Short Code : 2.5575MChip/s
R 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
2.5575MHz C
I
R 1 2 3 4 5 6 7 8 9 10
C
I Long Code : 2.5575MChip/s
R 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
C
1048575 Count10230 Count
Week reset Command
Register Inputs
I - InputR - Reset to initial conditionsC - Clock
Initial Phase Register
XOR
Initial Phase Register
Week reset port
Counter
G(X)=X20+X19+X16+X14+1
G(X)=X20+X19+X16+X14+1
G(X)=X10+X9+X6+X5+X4+X3+1
XOR
XOR
Initial Phase Register = All 1's
+
+
OR
Figure 5.7.1-2 Block diagram of LEX code generation
5.7.1.3.2 Code Generation
Separate 20-bit stage code generators are used to generate the two code patterns (Short Code and Long Code). The satellite numbers (PRN numbers) are identified by the default settings for each of these code generators. Table 5.7.1-1 shows the default values corresponding to the QZS satellite numbers. The initialization period for each code generator is 4 ms in the case of the Short Code generator and 410 ms in the case of the Long Code generator. Both the Short Code generator and the Long Code generator are initialized at the end/beginning of the week. Figure 5.7.2-3 shows the timing relationship between the LEX Short Code and Long Code.
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The PRN number is in accordance with Section 5.1.1.11.2.
Table 5.7.1-1 LEX code phase assignment
QZS SV ID PRN No. Initial shift register state
Short (Octal) Long (Octal)
1 193 0255021 0000304
2 194 0327455 0237663
3 195 0531421 0467237
4 196 0615350 0550370
5 197 0635477 1703243
The first digit in the octal notation represents first two chip (i.e. Most significant
digit “0” in the binary notation shall be ignored)
For example.:In the case of 3742246 in the octal notation, the first 20 chips are '11
111 100 010 010 100 110' in the binary notation
End/Start of Week End/Start of Week
Nav Message
LEX Short Code
LEX Long Code
1
0 Squarewave
LEX Short Code
LEX Long Code
LEX Signal (Chip by Chip Multiplexed Sinal)The first LEX Short Code starts synchronously with the end/start of week epoch
・・・・・・
・・・・・・L S L
Short Short
Long LongLong
S L S
1Symbol
10230Chips
1048575 Chips
Short ・・・・・・
・・・・・・
・・・・・・
1Symbol
10230Chips
10230Chips
1Symbol
1Symbol
10230Chips
1Symbol
1Symbol
1Symbol
1Symbol
10230Chips
10230Chips
10230Chips
1Symbol
1Symbol
1Symbol
1Symbol
10230Chips
10230Chips
10230Chips
10230Chips
10230Chips
1048575 Chips 1048575 Chips 997425 Chips
10230Chips
10230Chips
10230Chips
1Symbol
1Symbol
1Symbol
4 ms
410 ms
820 ms 390 ms
391 ns (=1/2.5575MHz)
195.5 ns (=1/5.115MHz)
Figure 5.7.1-3 Timing Relationship between the LEX Short Code and Long Code
5.7.1.3.3 Non-Standard Code
In the event that a problem with the QZSS occurs, a non-standard code (NSC) is transmitted. This is done to protect the user by ensuring that users do not use erroneous signals.
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5.7.2 LEX Messages
5.7.2.1 Message Structure
The LEX message signal structure is shown in Figure 5.7.2-1. Each message is made up of a total of 2,000 bits: a 49-bit header, a 1695-bit data section and a 256-bit Reed-Solomon code. Transmission of each Navigation message takes one second.
1 50 1745
1 33 41 49
"Alert" Flag - 1 Bit
Data Part(1695 Bits)
Header(49 Bits)
Reed-Solomon Code(256 Bits)
Preamble
32 Bits
PRN
8 Bits
Message Type ID
8 Bits
1 seconds
DIRECTION OF DATA FLOW FROM SV
2000 Bits
MSB LSB
Figure 5.7.2-1 LEX Message Structure
5.7.2.1.1 Preamble
At the beginning of each message is the 32-bit preamble. The value of the preamble is 00011010110011111111110000011101.
5.7.2.1.2 PRN No.
Each message has an 8-bit PRN number immediately following the preamble. The PRN number is the PRN number for the satellite transmitting that message.
5.7.2.1.3 Message Type ID
Each message has an 8-bit message type ID immediately following the PRN number. The message type ID signifies the information included in that frame. Table 5.7.2-1 shows the relationship between the message type ID and the information.
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Table 5.7.2-1 Definition of message type Message type Content Notes
0-9 Spare (System use)
10-19 10 Signal health (35 satellites) Ephemeris & SV clock (3 satellites)
For JAXA experiment
11 Signal health (35 satellites) Ephemeris & SV clock (2 satellites) Ionospheric correction
12~19 Spare
20 For experiment by Geographical Survey Institute
21~155 For experiment For experimental user except JAXA , GSI and users of application demonstration in private sector
156 - 255 For application demonstration in private sector For experimental users of application demonstration in private sector by means of performance enhancement signal
5.7.2.1.4 Alert Flag
Each message has a 1-bit alert flag immediately following the message type ID. The alert flag indicates the signal power of the LEX signal for that satellite and the health status of the data. During the experiment using message type 20 carried out by GSI, this “alert flag” bit is used for the identification which relevant data part is head of a message record or not. The data part includes the head of the message record if this bit is “1”, otherwise it is continuous message following previous message.
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5.7.2.1.5 FEC Encoded Algorithm
Reed-Solomon (255, 223) encoding is applied the 1,744 bits of the Navigation message (preamble, PRN, message type ID, alert flag and data section). Every 8 bits of the resulting bit-stream comprises one symbol. (see Section 6.5.1 for details) In order to add the 32-symbol (256-bit) Reed-Solomon code to the 218-symbol (1,744-bit) Navigation message, nine "0" symbols (72 bits) are inserted at the beginning of the 214-symbol (1,712-bit) data bit string that does not include the 4-symbol (32-bit) preamble at the beginning of the header. The resulting 223-symbol (1,784-bit) data bit string (with the 9 zero symbols inserted) is Reed-Solomon encoded (255,223) to generate a 32-symbol (256-bit) parity word. The 250 symbols (2,000 bits) that comprise the 32-symbol parity words added to the original 218-symbol (1,744-bit) data bit string (including the preamble) are then input to the CSK Modulator (see Figure 5.7.2-2).
214 Symbols (1712 Bits)
Parity (RSC)32 Symbols (256 Bits)
Zero “0”9 Symbols
Data Part
1695 Bits
Header
49 Bits
Preamble4 Symbols (32Bits)
Data Part
1695 Bits
Data Part
1695 Bits
Preamble4 Symbols (32Bits)
Header
49 Bits
Insert Zero “0” Symbol – 9 Symbols (72 Bits )
Delete Zero “0” Symbol – 9 Symbols (72 Bits )
223 Symbols (1784 Bits)
250 Symbols (2000 Bits)
Broadcast
Original Bit Strings
GF(28) RS(255,223) Encode
218 Symbols (1744 Bits)
Figure 5.7.2-2 Reed-Solomon Encoding
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5.7.2.2 Message Content
5.7.2.2.1 Message types 10 and 11
Message types 10 and 11 are JAXA test messages. The 1,695-bit data section of message type 10 includes the signal health and Ephemeris & SV clock data as shown in Figure 5.7.2-3. The 1,695-bit data section of message type 11 includes the signal health, Ephemeris & SV clock and ionospheric delay correction data as shown in Figure 5.7.2-4.
211 34 50 225
WN - 13 BitsTOW
501 702
1001 1179
1501 1656
Signal HealthPacket175 Bits
Ephemeris & SV ClockPacket 3
155 LSBs in 477Bits
Reserved
40 Bits
Ephemeris & SV ClockPacket 1
276 MSBs in 477Bits
Ephemeris & SV ClockPacket 2
299 MSBs in 477Bits
Ephemeris & SV ClockPacket 3
322 MSBs in 477Bits
Ephemeris & SV ClockPacket 1
201 LSBs in 477Bits
Ephemeris & SV ClockPacket 2
178 LSBs in 477Bits
20Bits
toe
16Bits
DIRECTION OF DATA FLOW FROM SV
500 Bits
DIRECTION OF DATA FLOW FROM SV
500 Bits
DIRECTION OF DATA FLOW FROM SV
500 Bits
DIRECTION OF DATA FLOW FROM SV
195 Bits
Figure 5.7.2-3 Data Part, Message Type 10 – Signal Health, Ephemeris & SV Clock
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211 34 50 225
WN - 13 BitsTOW
501 702
1001 1179 1391
1501
Ephemeris & SV ClockPacket 1
276 MSBs in 477Bits
Ephemeris & SV ClockPacket 2
299 MSBs in 477Bits
Ionospheric CorectionPacket212 Bits
Reserved
110 Bits
Reserved
195 Bits
Ephemeris & SV ClockPacket 1
201 LSBs in 477Bits
Ephemeris & SV ClockPacket 2
178 LSBs in 477Bits
20Bits
toe
16Bits
Signal HealthPacket175 Bits
DIRECTION OF DATA FLOW FROM SV
500 Bits
DIRECTION OF DATA FLOW FROM SV
500 Bits
DIRECTION OF DATA FLOW FROM SV
500 Bits
DIRECTION OF DATA FLOW FROM SV
195 Bits
Figure 5.7.2-4 Data Part, Message Type 11 – Signal Health, Ephemeris & SV Clock and Ionospheric Correction
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5.7.2.2.1.1 Content of Message Types 10 and 11
(1) TOW Count The 20-bit Time of Week (TOW) count at the beginning of the data section of message types 10 and 11 indicates the time (seconds into week) at the beginning of the next one-second message. The valid range is from 0 to 604799. The TOW included in the last message of the week is 0. The TOW included in the first message of the week is 1.
(2) Transmission Week No. (WN) The 13 bits from bit 21 to bit 33 in the data section of message types 10 and 11 constitute a binary expression for the modulo-8192 GPS Week Number at the start of that message.
(3) Epoch for Ephemeris & SV clock parameters (toe) The 16 bits from bit 34 through bit 49 in the data section of message types 10 and 11 constitute the epoch for the Ephemeris & SV clock parameters stored in that message.
(4) Signal Health Bits 50-224 in the data section of message types 10 and 11 constitute a signal health packet. As shown in Figure 5.7.2-5, the signal health values for the three QZS satellites and the 32 GPS satellites are broadcast in one batch. The signal health for each QZS and GPS satellite is expressed in five bits (made up of five 1-bit signal health flags) indicating the health of the L1, L2, L5, L1C and LEX signals in that order. When there is a problem with the signal for the corresponding satellite, the 1-bit signal health flag for the L1, L2, L5 or L1C signal will be set to "1”. In such cases, the pseudorange for that signal for the corresponding satellite must not be used for range calculations. The 1-bit signal health flag for the LEX signal changes to "1" when there is a problem with the Ephemeris & SV clock parameters for that satellite that are being broadcast by the QZS. In such cases, the LEX signal (from that satellite) must not be used for range calculations. Signal Health Flag Value Definition 0 There is no problem with the signal 1 There is a problem with the signal and the data cannot be used
(5) Ephemeris & SV Clock Packet Bits 225-701, bits 702-1178 and bits 1179-1655 in the data section of message type 10, and bits 225-701 and bits 702-1178 in the data section of message type 11, each constitute an Ephemeris & SV clock packet. Each Ephemeris & SV clock packet includes a satellite ID for one satellite (SV ID), a User Range Accuracy (URA) indicator, the Ephemeris, the SV clock and the group delay correction parameter. For more information, see Section 5.7.2.2.1.2.
(6) Ionospheric Correction Parameter Packet Bits 1179-1390 in the data section of message types 10 and 11 constitute an ionospheric correction packet. For more information, see Section 5.7.2.2.1.3.
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1 6 11 16 21 26 31 36 41 46
51 56 61 66 71 76 81 86 91 96
101 106 111 116 121 126 131 136 141 146
151 156 161 166 171
GPS 16
5 Bits
GPS 17
5 Bits
GPS 18
5 Bits
GPS 19
5 Bits
GPS 20
5 Bits
GPS 21
5 Bits
GPS 22
5 Bits
GPS 23
5 Bits
GPS 24
5 Bits
GPS 25
5 Bits
GPS 2
5 Bits
GPS 3
5 Bits
GPS 4
5 Bits
GPS 5
5 Bits
QZS 1
5 Bits
QZS 2
5 Bits
QZS 3
5 Bits
GPS 1
5 Bits
GPS 6
5 Bits
GPS 7
5 Bits
GPS 8
5 Bits
GPS 9
5 Bits
GPS 10
5 Bits
GPS 11
5 Bits
GPS 12
5 Bits
GPS 13
5 Bits
GPS 14
5 Bits
GPS 15
5 Bits
GPS 26
5 Bits
GPS 27
5 Bits
GPS 28
5 Bits
GPS 29
5 Bits
GPS 30
5 Bits
GPS 32
5 Bits
GPS 31
5 Bits
DIRECTION OF DATA FLOW FROM SV
50 Bits
DIRECTION OF DATA FLOW FROM SV
50 Bits
DIRECTION OF DATA FLOW FROM SV
50 Bits
DIRECTION OF DATA FLOW FROM SV
25 Bits
Figure 5.7.2-5 Signal Health Packet Structure
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5.7.2.2.1.2 Content of Message Types 10 and 11 (Ephemeris & SV Clock Packet)
(1) Ephemeris & SV clock Packet The Ephemeris & SV clock packet for each satellite is made up of 477 bits, as shown in Figure 5.7.2-6.
(2) Satellite ID: SV ID The first 8 bits of each Ephemeris & SV clock packet constitute a satellite ID (SV ID). The SV ID indicates the PRN number for the satellite corresponding to that data packet. When the SV ID is set to all 1’s ("11111111"), it indicates that the packet does not contain Ephemeris & SV clock data. In such cases, the remaining data bits of that packet will consist of alternating "1" and "0" values starting with 1.
(3) User Range Accuracy (URA) Indicator Bits 9-12 of the Ephemeris & SV clock packet constitute an accuracy indicator for the corresponding satellite. The URA index (N) is an integer from 0 to 15. This value has the following relationship with the user range accuracy (URA) of the satellite.
URA index(N) URA (meters)
0 URA ≦ 0.08 1 0.08 < URA ≦ 0.11 2 0.11 < URA ≦ 0.15 3 0.15 < URA ≦ 0.21 4 0.21 < URA ≦ 0.30 5 0.30 < URA ≦ 0.43 6 0.43 < URA ≦ 0.60 7 0.60 < URA ≦ 0.85 8 0.85 < URA ≦ 1.20 9 1.20 < URA ≦ 1.70 10 1.70 < URA ≦ 2.40 11 2.40 < URA ≦ 3.40 12 3.40 < URA ≦ 4.85 13 4.85 < URA ≦ 6.85 14 6.85 < URA ≦ 9.65 15 9.65 < URA ( or no accuracy prediction available)
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(4) Ephemeris
(a) Ephemeris parameter properties The properties of the Ephemeris parameters for message types 10 and 11 (number of bits, LSB scale factor and units) are in accordance with Table 5.7.2-2.
(b) User Algorithm for Determining Satellite Position
The satellite antenna phase center position in the ECEF system (x, y, z) should be calculated using the following equations.
][)(61)(
21)( 32 mttJERKxttACCxttVELxPOSxx oeoeoe
][)(61)(
21)( 32 mttJERKyttACCyttVELyPOSyy oeoeoe
][)(61)(
21)( 32 mttJERKzttACCzttVELzPOSzz oeoeoe
t : Satellite time. This is the same as the t value discussed in Section 6.3.2. For
cases when the satellite time value extends beyond the end of the week (and the beginning of the following week), if oett is greater than 302,400 seconds, 604,800 seconds should be subtracted; if t-toe is less than -302,400 seconds, 604,800 seconds should be added.
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1 9 13 46 79
URA
101 112 140 168 196
201 220 244 268 288
301 308 328 354 374 387 400
ISCL2C - 1 MSBJERKy
401 413 426 439 452 465
POSy
33 Bits
JERKx
20 Bits
POSz
22 MSBs
POSz
11 LSBs
VELx
28 Bits
VELy
28 Bits
VELz
28 Bits
ACCx5
MSBs
SV ID
8 Bits4
Bits
POSx
33 Bits
JERKy
13MSBs
7LSBs
JERKz
20 Bits
Af0
26 Bits
Af1
20 Bits
TGD
13 Bits
ISCL1C/A
13 Bits
ACCy
24 Bits
ACCz
24 Bits
ACCx
19 LSBs
ISCL1CD
13 Bits
ISCLEX
13 Bits
ISCL2C
12 LSBs
ISCL5I5
13 Bits
ISCL5Q5
13 Bits
ISCL1CP
13 Bits
DIRECTION OF DATA FLOW FROM SV
100 Bits
DIRECTION OF DATA FLOW FROM SV
100 Bits
DIRECTION OF DATA FLOW FROM SV
100 Bits
DIRECTION OF DATA FLOW FROM SV
77 Bits
DIRECTION OF DATA FLOW FROM SV
100 Bits
Figure 5.7.2-6 Ephemeris & SV Clock Packet Content
URA index
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Table 5.7.2-2 Definition of ephemeris parameters for Navigational Message DLEX navigation message Parameter No. of Bits Scale Factor
(LSB)
Units
WN GPS Week Number 13 1 Weeks
oet Ephemeris epoch (seconds into week) 16 15 Seconds
SV ID PRN number (range 0 - 255) for satellite
for which ephemeris parameter will be
applied.
1-32 for GPS; 193-197 for QZSS
8 - -
URA index User range accuracy index 4 - -
POSx X coordinate : Position coefficient 33* 2-6 m
POSy Y coordinate : Position coefficient 33* 2-6 m
POSz Z coordinate : Position coefficient 33* 2-6 m
VELx X coordinate : Velocity coefficient 28* 2-15 m/s
VELy Y coordinate : Velocity coefficient 28* 2-15 m/s
VELz Z coordinate : Velocity coefficient 28* 2-15 m/s
ACCx X coordinate : Acceleration coefficient 24* 2-24 m/s2
ACCy Y coordinate : Acceleration coefficient 24* 2-24 m/s2
ACCz Z coordinate : Acceleration coefficient 24* 2-24 m/s2
JERKx X coordinate : Jerk coefficient 20* 2-32 m/s3
JERKy Y coordinate : Jerk coefficient 20* 2-32 m/s3
JERKz Z coordinate : Jerk coefficient 20* 2-32 m/s3
* Parameters so indicated are in two’s complement notation.
(5) SV Clock Parameter
(a) Properties of SV Clock Parameter The properties of the SV clock parameter in message types 10 and 11 (number of bits, LSB scale factor and units) are in accordance with Table 5.7.2-3.
(b) User Algorithm for SV Clock Correction
With the exception of the relativistic effect, the time offset )(ttc with respect to QZSST is calculated using the following equation. The handling of other SV clock offsets is in accordance with Section 6.3.2.
oeffc ttAAtt 10)( [s] t : Satellite time. This is the same as the t value discussed in Section 6.3.2. For
cases when the satellite time value extends beyond the end of the week (and the beginning of the following week), if oett is greater than 302,400 seconds, 604,800 seconds should be subtracted; if t-toe is less than -302,400 seconds, 604,800 seconds should be added.
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(6) Group Delay Correction Parameter
(a) Properties of Group Delay Correction Parameter The properties of the group delay parameter in message types 10 and 11 (number of bits, LSB scale factor and units) are in accordance with Table 5.7.2-3. If the Group Delay Correction Parameters are set to "1000000000000", this indicates that the group delay parameter cannot be used.
(b) Single-Signal User Algorithm for Group Delay Correction Parameter User receivers calculating range using measurements of only the LEX signal pseudorange must use the following equation to correct the SV clock offset for the QZS. For more information on correcting the SV clock offset for GPS, see Applicable Documents (1), (2) and (3). When ranging is conducted by combining different frequency signals from QZS and GPS satellites, the receiver internal group delay must be properly corrected by the user receiver. rLEXGDcLEXsv tISCTtt [s]
ct : Time offset with respect to QZSST with the exception of the relativistic effect
rt : Relativistic effect offset (as shown in Section 6.3.2)
(c) Dual-Signal User Algorithm for Group Delay Correction Parameter User receivers calculating range using measurements of the LEX signal pseudorange and the pseudorange of another QZS or GPS signal, must use the following procedure for correction of the ionospheric delay and SV clock offset. In addition, based on the definition of tsv shown in Section 6.3.2, the transmitted values for L1C/AISC are going to be as follows: 0ISC A/C1L Correction of the GPS ionospheric delay and SV clock offset is in accordance with Applicable Documents (1), (2) and (3). When ranging is conducted by combining different frequency signals from QZS and GPS satellites, the receiver internal group delay must be properly corrected by the user receiver.
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(i) Dual-Signal Users of L1C/A and LEX Signals User receivers calculating range using measurements of the L1C/A and LEX signals should use the following equation to correct the ionospheric delay.
svGD
EX1
A/C1LEX1LEXA/C1LEX1LEXA/C1LLEX tccT
1ISCISCcPRPRPR
[m] where
A/C1LLEXPR : Pseudorange value corrected for the ionospheric delay and SV clock offset
LEXA/C1L PR,PR : Pseudorange values observed using two signals 2
EX1 125154
: Square of the ratio of the L1 to LEX signal frequencies
svt : Time offset with respect to QZSST including relativistic effect
rt : Relativistic effect correction indicated in Section 6.3.2
c : Speed of light indicated in Section 6.1.1 (ii) Dual-Signal Users of L2C and LEX Signals User receivers calculating range using measurements of the L2C and LEX signals should use the following equation to correct the ionospheric delay.
svGD
2EX
LEX2EXC2LLEX2EXC2LLEXC2L tccT
1ISCISCcPRPRPR
[m] where
LEXC2LPR : Pseudorange value corrected for the ionospheric delay and SV clock offset
LEXC2L PR,PR : Pseudorange values observed using two signals 2
2EX 120125
:
Square of the ratio of the L1 and L2C to LEX signal frequencies
svt : Time offset with respect to QZSST including relativistic effect
rt : Relativistic effect correction indicated in Section 6.3.2
c : Speed of light indicated in Section 6.1.1
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(iii) Dual-Signal Users of L5 and LEX Signals User receivers calculating range using measurements of the L5 and LEX signals should use the following equation to correct the ionospheric delay.
svGD
5EX
LEX5EX5LLEX5EX5LLEX5L tccT
1ISCISCcPRPRPR
[m]
where
LEXLPR 5 : Pseudorange value corrected for the ionospheric delay and SV clock offset
LEXL PRPR ,5 : Pseudorange values observed using two signals (L5 and LEX) (In the case of the L5 signal, either the L5I signal or the L5Q signal)
2
5 115125
EX : Square of the ratio of the LEX to L5 signal frequencies
svt : Time offset with respect to QZSST including relativistic effect
rt : Relativistic effect correction indicated in Section 6.3.2
c : Speed of light indicated in Section 6.1.1 (iv) Dual-Signal Users of L1C and LEX Signals User receivers calculating range using measurements of the L1C and LEX signals should use the following equation to correct the ionospheric delay.
svGD
EX1
C1LEX1LEXC1LEX1LEXC1LLEX tccT
1ISCISCcPRPRPR
[m] where
C1LLEXPR : Pseudorange value corrected for the ionospheric delay and SV clock offset
LEXC1L PR,PR : Pseudorange values observed using two signals (L1C and LEX) (In the case of the L1C signal, either the L1CP signal or the L1CD signal)
2
EX1 125154
: Square of the ratio of the L1C to LEX signal frequencies
svt : Time offset with respect to QZSST including relativistic effect
rt : Relativistic effect correction indicated in Section 6.3.2
c : Speed of light indicated in Section 6.1.1
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Table 5.7.2-3 Definition of SV clock and group delay parameters for Navigational Message DLEX navigation messages
Parameter No. of Bits Scale Factor
(LSB)
Units
0fA SV clock bias correction coefficient 26* 2-35 s
1fA SV clock drift correction coefficient 20* 2-48 s/s
TGD 13* 2-35 s
ISCL1C/A (Zero “0” in the case of QZS) 13* 2-35 s
ISCL2C 13* 2-35 s
ISCL5I5 13* 2-35
ISCL5Q5 13* 2-35 s
ISCL1CP 13* 2-35 s
ISCL1CD 13* 2-35 s
ISCLEX 13* 2-35 s
* Parameters so indicated are in two’s complement notation.
5.7.2.2.1.3 Content of Message Type 11 (ionospheric correction packet)
(1) Ionospheric Correction Parameter Packet The ionospheric correction parameter packet is made up of 212 bits, as shown in Figure 5.7.2-7.
(2) Properties of Ionospheric Correction Parameter The properties of the ionospheric correction parameter for message type 11 (number of bit, LSB scale factor and units) are in accordance with Table 5.7.2-4. When the ionospheric delay correction standard time is set to all 1’s ("11111111111111111111"), it indicates that the packet does not contain an ionospheric delay correction parameter. In such cases, the remaining data bits of that packet will consist of alternating "1" and "0" values starting with 1. The ionospheric delay correction parameter should only be used during the valid time (TSPAN) starting from the time expressed by the ionospheric delay correction standard Week Number (WNIONO) and the ionospheric delay correction standard time (TIONO). The ionospheric delay correction parameter should be used only when the user receiver latitude and longitude are within the domain indicated in Figure 4.1.5-1 of Section 4.1.5.
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Table 5.7.2-4 Definition of ionospheric correction parameters for LEX navigation messages Parameter No. of Bits Scale Factor
(LSB)
Units
tIONO
Reference time of week for ionospheric correction
20 1 seconds
WNIONO Reference Week Number for ionospheric correction
13 1 weeks
TSPAN Valid time 8 1 minute φ0
Latitude coordinates of the origin of approximate function
19* 0.00001 radian
λ0 Longitude coordinates of the origin of approximate function
20* 0.00001 radian
E00 Coefficient of approximate function 0-0 degree (latitude-longitude)
22* 0.001 m
E10 Coefficient of approximate function 1-0 degree (latitude-longitude)
22* 0.01 m/radian
E20 Coefficient of approximate function 2-0 degree (latitude-longitude)
22* 0.01 m/radian2
E01 Coefficient of approximate function 0-1 degree (latitude-longitude)
22* 0.01 m/radian
E11 Coefficient of approximate function 1-1 degree (latitude-longitude)
22* 0.01 m/radian2
E21 Coefficient of approximate function 2-1 degree (latitude-longitude)
22* 0.1 m/radian3
* Parameters so indicated are in two’s complement notation.
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1 21 34 42
51 61 81
101 103 125 147
151 169 191
201
WNIONO
13 Bits
TSPAN
8 Bits
φ 0
9 MSBs
λ 0
20 Bits
E00
20 MSBs
tIONO
20 Bits
E21
10 MSBs
φ 0
10 LSBs
E21
12 LSBs
E01
18 LSBs
E11
22 Bits
E01
4 MSBs
E10
22 Bits
E20
22 Bits
DIRECTION OF DATA FLOW FROM SV
50 Bits
DIRECTION OF DATA FLOW FROM SV
50 Bits
DIRECTION OF DATA FLOW FROM SV
50 Bits
DIRECTION OF DATA FLOW FROM SV
50 Bits
DIRECTION OF DATA FLOW FROM SV
12 Bits
E00 - 2 LSBs
Figure 5.7.2-7 Ionospheric Correction Packet Content
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(3) User Algorithm for Ionospheric Correction User receivers calculating range using measurements of only one signal should correct the ionospheric delay using the following ionospheric model. Satellite transmission parameters
00 , : Latitude and longitude of the origin of approximate function in the coordinate system defined in Section 3.1.4.2 [rad]
nmE : Approximate function coefficient
Receiver generation parameters El : Elevation angle between user receiver and satellite [rad] Az : Azimuth angle between user receiver and satellite [rad]
r : Latitude of user receiver in the coordinate system defined in Section 3.1.4.2 [rad]
r : Longitude of user receiver in the coordinate system defined in Section 3.1.4.2 [rad]
Constants a : Equatorial radius of the Earth in the coordinate system defined in Section 3.1.4.2 a = in accordance with Section 6.2.2.1.4 [m]
ionoH : Height of ionospheric shell above the Earth 000,350ionoH [m]
Lx : Square of ratio of Lx frequency (x = 2, 5, EX) to L1 frequency
22
5
2
21 125154,
115154,
120154,1
LEXLLL [-]
Calculation parameters Lxiono tT )( : Diagonal ionospheric delay of frequency LX (X = 1, 2, 5, EX)
)(tF : Inclination factor )(tpp : Pierce point latitude in the coordinate system defined in Section 3.1.4.2
)(tpp : Pierce point longitude in the coordinate system defined in Section 3.1.4.2
)(tpp : Angle formed by pierce point-earth's center-user receiver [rad]
Computational expressions - Lxiono tT )( : Diagonal ionospheric delay of frequency X
mpp
npp
n mnmLxLxiono ttEtFtT ))(())(()()( 00
2
0
1
0
[m]
- tF : Inclination factor
2cos11
ionoHatElatF [-]
- )(tpp : Pierce point latitude
tAzttt pprpprpp cossincoscossinsin 1 [rad]
- )(tpp : Pierce point longitude
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rpprpp
pprpp tAztt
tAztt
sin)(cos)(sincos)(cossinsin
tan 1 [rad]
- )(tpp : Angle formed by pierce point-earth's center-user receiver
)(cossin)(
2)( 1 tEl
HaatElt
ionopp
[rad]
5.7.2.2.1.4 Broadcast Period, Updating Period and Valid Time
(1) Broadcast Period The sequence for broadcasting message types 10 and 11 is arbitrary under the condition as shown in Table 5.7.2-5.
(2) Updating Period Table 5.7.2-5 shows the nominal updating periods for the messages parameters included in message types 10 and 11.
(3) Validity Time Table 5.7.2-5 shows the nominal valid time for the messages included in message types 10 and 11.
Table 5.7.2-5 Message type 10,11:broadcast interval, update interval and valid time Message data
Nominal broadcast
interval
Nominal update
interval
Nominal valid time
Signal health 1 second 1 seconds -
Ephemeris 12 seconds 3 minutes 6 minutes
SV clock 12 seconds 3 minutes 6 minutes
Ionospheric correction 12 seconds 30 minutes -
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5.7.2.2.2 Message Types 20
Message type 20 is to be used for the experiment conducted by Geographical Survey Institute(GSI).
(1) Record structure The record structure of message type 20 is shown in Table 5.7.2-6. A record is divided consecutively into every 1,695 bits as 1 packet. Every packet is transmitted in every second. In the case that the end of record appears in the middle of a packet, the value of the rest of the packet is indefinite. One packet shall not contain two or more records. The alert flag defined in Section 5.7.2.1.4 is used for identifying the first packet of the record.
Table 5.7.2-6 The Record Structure of Message Type 20 # Name Data Type Data Size Content possible range Assigned Value
1 Compression Type uint2 2bits Type of compression applied for the parameter part
0~3 0=no compression 1=zip compression 2~3=undefined
2 Length of Parameter
Part
uint14 14bits Data length of parameter part in bytes (N)
0~16,383
3 Parameter Part char*N N*8bits
Augmentation parameters of one of the four types in original or compressed form. See (3)~(6) for the detail of each parameter type.
4 CRC char*3 24bits CRC-24Q
Total (5+N)*8 bits
*The “CRC", #4 in Table 5.7.2-6, is calculated for (3+N)×8 [bits] composed of #1, “Compression Type”, with adding fixed “11010011" (8[bits]) on top, #2 “Length of Parameter Part”, and #3, “Parameter Part”. “#CRC-24Q” is a 24-bit CRC: the generator polynomial, G(X), is expressed as follows. 13456710111417182324 XXXXXXXXXXXXXXG
(2) Parameter-type ID Table 5.7.2-7 shows contents of four defined Parameter-type IDs. Table 5.7.2-7 Parameter-type ID
Parameter-type ID Contents Note
0 Observation information of the reference stations See Table 5.7.2-8
1 Satellite orbit & clock correction information, ionosphere grid interval information
See Table 5.7.2-11
2 Tropospheric delay correction information See Table 5.7.2-12
3 Ionospheric delay correction information See Table 5.7.2-13
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(3) Observation information of the reference stations
Table 5.7.2-8 Observation Information of the Reference Stations
Observation information of the reference stations(Parameter-type ID=0)
# Name Data Type Data Size
Possible range Assigned value Remarks
1 Parameter-type ID uint4 4 bits 0~15 0
2 Area number Indicator uint4 4 bits 0~15 No. of Areas-1 11 for 12 area setting
#3~15 are repeated for each Area(1~No. of areas)
3 Area ID uint4 4 bits 0~15 1~12
4 Reference Station ID in each Area
uint2 2 bits 0~3 0~1
5 GPS Epoch Time uint30 30 bits 0~604,799,999 Resolution:1msec In Time of Week
DF004
6 No. of GPS Satellites (NSV)
uint5 5 bits 0~31 DF006
7 GPS Divergence-free Smoothing Indicator
bit(1) 1 bits 0,1 Divergence-free Smoothing 0 = not used 1 = used
DF007
8 GPS Smoothing Interval bit(3) 3 bits 0~7 See Table 5.7.2-9 DF008
Total of #3~#8 45 bits
#9~15 are repeated for each satellite(1~NSV)
9 GPS Satellite ID uint6 6 bits 0~63 1~32(PRN number for GPS)
10 GPS L1 Code Indicator bit(1) 1 bits 0,1 0 = C/A Code 1 = P(Y) Code Direct
DF010
11 GPS L1 Pseudorange
uint24 24 bits 0~14,989,623 (0~299,792.46m)
Resolution:0.02m Residue modulo 299,792.458m
DF011
12 GPS L1 Phase Range-L1 Pseudorange
int20 20 bits -524,288 ~524,287 (-262.1440 ~262.1435m)
Resolution:0.0005m At start up and after each cycle slip, the initial ambiguity is reset and chosen so that the L1 Phase Range should match the L1 Pseudorange as closely as possible (i.e., the value of GPS L1 Phase Range – L1 Pseudorange is to be close to 0.) If the GPS L1 Phase Range –L1 Pseudorange diverges over time across the range limits defined, the computed value needs to be adjusted (rolled over) by the equivalent of 1500 cycles in order to bring the value back within the defined range in the left column.
DF012
13 GPS L1 Lock time Indicator
uint7 7 bits 0~127 See Table 5.7.2-10 DF013
14 GPS L1 Pseudorange Modulus Ambiguity
uint8 8 bits 0~255 (0~ 76,447,076.790m)
Resolution:299,792.458m DF014
15 GPS L1 CNR uint8 8 bits 0~255 (0~63.75dB-Hz)
Resolution:0.25dB-Hz DF015
- Total of #9~#15 74 bits
Total(All) 8+NA*(45+NSV*74) bits
For #9, “GPS Satellite ID”, value from “1” to “32” is assigned to the satellite’s GPS PRN number, and the other values are not used.
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Content and format of some of the items follows RTCM standards version 3.0. A notation that starts with “DF” in the column “Remarks” indicates the corresponding Data Field in the documentation of RTCM version 3.0.
Table 5.7.2-9 GPS Smoothing Interval Indicator Smoothing Interval
000 (0) No smoothing applied
001 (1) <30 sec
010 (2) 30-60 sec
011 (3) 1-2 min
100 (4) 2-4 min
101 (5) 4-8 min
110 (6) >8 min
111 (7) Unlimited smoothing interval
Table 5.7.2-10 GPS L1 Lock time Indicator Indicator(i) Minimum Lock Time
(in seconds)
Range of Indicated Lock Times
(in seconds)
1~23 i 1≦lock time<24
24~47 i *2-24 24≦lock time<72
48~71 i *4-120 72≦lock time<168
72~95 i *8-408 168≦lock time<360
96~119 i *16-1,176 360≦lock time<744
120~126 i *32-3,096 744≦lock time<937
127 lock time≧937
If a cycle slip occurs during the previous measurement cycle, the lock indicator will be reset to zero.
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(4) Satellite Orbit and Clock correction Information + Ionosphere Grid Interval Information
Table 5.7.2-11 Satellite Orbit and Clock Correction Information + Ionosphere Grid Interval Information Satellite Orbit and Clock Correction Information + Ionosphere Grid Interval Information(Parameter-type ID=1)
# Name Data
Type
Data Size Content Possible range Assigned value
1 Parameter-type ID uint4 4 bits 0~15 1
2 DOY uint9 9 bits Day of year in days 0~366
3 TOD uint7 7 bits Time of day on the initial orbit epoch
0~95 (0~1425 min)
Resolution: 15min
4 Version uint12 12 bits Version of auxiliary information used to generate correction parameters
0~4095
5 Grid interval in Latitude
uint4 4 bits Latitudinal grid interval of ionospheric correction model
1~15 (0.05~0.75deg)
Resolution: 0.05deg
6 Grid interval in Longitude
uint4 4 bits Longitudinal grid interval of ionospheric correction model
ditto Ditto
7 No. of Orbit Epochs (NORB)
uint4 4 bits Number of Satellite orbit epochs
0~15 13
8 No. of Satellites (NSV)
uint5 5 bits Number of Satellites 0~31
#9~14 are repeated for each satellite (1~NSV)
9 Satellite ID uint6 6 bits Satellite ID (PRN number for GPS)
0~63 1~32(GPS)
10 Satellite Health status uint1 1 bits Satellite Health status 0,1 0=Unhealthy 1=Good
#11~14 are repeated for each orbit epoch (1~NORB)
11 Satellite Position X int37 37 bits Satellite position X-coordinate
-68,719,476,736 ~68,719,476,735
Resolution:1mm
12 Satellite Position Y int37 37 bits Satellite position Y-coordinate
-68,719,476,736 ~68,719,476,735
Resolution:1mm
13 Satellite Position Z int37 37 bits Satellite position Z-coordinate
-68,719,476,736 ~68,719,476,735
Resolution:1mm
14 Satellite Clock offset int31 31 bits Satellite clock offset -1,073,741,824 ~1,073,741,823 (-1,073.741824 ~1,073.741823μsec)
Resolution:10-6
μsec
Total 49+NSV*{7+NORB*(37+37+37+31)} bits
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(5) Tropospheric Delay Correction Information
Table 5.7.2-12 Tropospheric Delay Correction Information Tropospheric Delay Correction Information(Parameter-type ID=2)
# Name Data Type Data Size Content Possible Range Assigned value
1 Parameter-type ID int4 4 bits 0~15 2
2 TOW uint20 20 bits GPS Epoch Time (Time of Week)
0~604,799 Resolution :1sec
3 No. of GPS-Based Control Stations (NSTN)
uint11 11 bits Number of GPS-based control stations
0~2,047 NSTN:~1200
#4~5 are repeated for each GPS-based control station (1~NSTN)
4 GPS-Based Control Station ID
uint11 11 bits GPS-based control station ID
0~2,047
5 Zenith Wet Delay uint11 11 bits Zenith wet delay in mm 0~2,047
Total 35+NSTN*(11+11) bits
(6) Ionospheric Delay Correction Information
Table 5.7.2-13 Ionospheric Delay Correction Information Ionospheric Delay Correction Information(Parameter-type ID=3)
# Name Data Type Data Size Content Possible range Assigned value
1 Parameter-type ID Uint4 4 bits 0~15 3
2 Area ID Uint4 4 bits Area ID 0~15 1~12
3 TOW Uint20 20 bits GPS Epoch time (Time of Week)
0~604,799 Resolution: 1sec
4 No. of grid maps Uint5 5 bits Number of grid maps (= Number of satellites)
0~31
#5~10 are repeated for each grid map (k=1~number of grid maps)
5 Satellite ID Uint6 6 bits Satellite ID 0~63 1~32(GPS)
6 Lowest latitude int12 12 bits Northern latitude of the first row
±1,800 (±90deg) Resolution: 0.05deg
7 No. of Rows (Lk)
Uint8 8 bits Total number of rows in the k-th grid map(Lk)
0~255
#8~10 are repeated for each row (i=1~Lk)
8 Lowest longitude int13 13 bits Eastern longitude of the first grid point in the row
±3,600 (±180deg) Resolution: 0.05deg
9 No. of grid points (Mk,i)
uint8 8 bits Total number of grid points (Mk,i) in the i-th row of the k-th grid map
0~255
#10 is a repeated for each grid point (j=1~Mk,i)
10 VTEC uint14 14 bits VTEC (total electron content of zenith direction) value at a grid point (i,j)
0~16,383 (0~163.82 TECU. If 16,383, it indicates anomalous Value)
Resolution: 0.01TECU
Total
k iikk ML ,14212633
bits for one area
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5.7.2.2.3 Message Types 21 - 155
Message types 21-155 are for general public user testing by entities. Test personnel may store 1,695 bits of arbitrarily created data in the data section of message types 21-155. However, when message types 10, 11 (for JAXA testing), message type 20 (for GSI testing) or message type 156-255 (for application demonstration in private sector) are being broadcast, message types 21-155 will not be broadcast.
5.7.2.2.4 Message Types 156-255
Message types 156-255 are for application demonstration in private sector. The contents of data are described in Applicable document (6). Satellite Positioning Research and Application Center manages usage of message types 156-255
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6 User Algorithms
6.1 Constants
6.1.1 Speed of Light
Same as Section 20.3.3.3.3.1 in Applicable Document (1). Expressed using a small letter "c". The value is ]/[299792458 smc .
6.1.2 Angular Velocity of the Earth's Rotation
Same as Table 20-IV in Applicable Document (1). Expressed using the Greek symbol " e ". The value is ]/[102921151467.7 5 srade
.
6.1.3 Earth's Gravitational Constant
Same as Table 20-IV in Applicable Document (1). Expressed using the Greek symbol " ". The value is ]/[10986005.3 2314 sm .
6.1.4 Circular Constant
Same as Section 20.3.3.4.3.2 in Applicable Document (1). Expressed using the Greek symbol " ". The value is 8981415926535.3 .
6.1.5 Semi-Circle
Same as in Applicable Document (1). Expressed as the circular constant " " in Section 6.1.4.
6.2 User algorithms relating to time systems and coordinate systems
6.2.1 User algorithms relating to time systems
QZSS is based on the following time relationships.
(a) Each satellite is operated in accordance with its own SV clock.
(b) All time relationship data (TOW) are generated by the SV clock.
(c) All other data in navigation messages are relative to GPS time.
(d) Navigational messages are transmitted with reference to the SV clock.
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6.2.2 User Algorithms relating to Coordinate Systems
6.2.2.1 Earth-Centered, Earth-Fixed (ECEF) Coordinate System Constant
The Earth-Centered, Earth-Fixed (ECEF) coordinate system referred to in this document is defined as follows.
(a) Origin: Earth's center of mass (b) Z-axis: International Earth Rotation and Reference Systems Service (IERS) pole direction (c) X-axis: Direction of intersection of IERS Reference Meridian (IRM) and the plane
containing the origin and the Z-axis (d) Y-axis: Direction formed by the right-hand fixed geocentric coordinate system
6.2.2.1.1 QZSS Earth-Centered, Earth-Fixed (ECEF) Coordinate System
The Earth-Centered, Earth-Fixed (ECEF) coordinate system used by QZSS is known as the Japan satellite navigation Geodetic System (JGS). It is defined in Section 3.1.4.2.
6.2.2.1.2 Relationship between GPS Earth-Centered, Earth-Fixed (ECEF) coordinate system and
QZSS ECEF coordinate system
The GPS Earth-Centered, Earth-Fixed (ECEF) coordinate system is known as the World Geodetic System 1984 (WGS84). It is defined Section 20.4.3.3.1 in Applicable Document (1). The relationship between WGS84 and JGS is covered in Section 3.2.2.
6.2.2.1.3 Differences in JGS and WGS84 ellipsoids and the effect of these differences
JGS uses the Geodetic Reference System 1980 (GRS80) ellipsoid, while WGS84 uses the WGS84 ellipsoid. The differences between these ellipsoids affect primarily the angle of elevation calculation that must be performed in the process of calculating the ionospheric delay correction. However, as these two ellipsoids are virtually identical, in practical terms there is no difference.
(a) GRS80 ellipsoid
a = 6,378,137 m f = 1/298.257222101
(b) WGS84 ellipsoid a = 6,378,137 m f = 1/298.257223563
6.2.2.2 Satellite position as determined by orbit calculations
The positions of the satellites in each system as determined in Section 6.3.5 indicate the antenna phase center position in the Earth-Centered, Earth-Fixed (ECEF) coordinate system defined by each system as noted in Section 6.2.2.1.
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6.3 Common GNSS Algorithms
6.3.1 Time Relationships
6.3.1.1 Value Calculated using Time
Many parameters relating to satellite status change over time. These parameters are time functions that have coefficients in the navigation messages and are calculated by the user. Calculations are a function of the difference in epoch between the current time and each of the parameters. These parameters include the following:
(a) SV clock correction (Section 6.3.2) (b) Satellite orbit calculation kkkkkkkkk iruvEMt ,,,,,,,, (Section 6.3.5 and 6.3.6)
(c) UTC (Section 6.3.7)
6.3.1.2 Epoch Set at Master Control Station
In general, these epochs are established by the Master Control Station (MCS) as follows.
(1) oet : Ephemeris data epoch The minimum update period for Ephemeris data is one hour. The curve fit interval is two hours. The epoch is set near the center of the curve fit interval. Even if the updating period and the curve fit interval are extended, this relationship (of the epoch being set near the middle of the curve fit interval) will be maintained.
(2) oct : SV clock parameter epoch The minimum update period for SV clock parameters is 900 seconds. The curve fit interval is 1800 seconds. The epoch is the same as the epoch for the Ephemeris data that are transmitted at the same time. Even if the updating period and the curve fit interval are extended, this relationship (of the epoch being the same as that of the Ephemeris data) will be maintained.
(3) oat : Almanac data epoch The minimum update period for Almanac data is approximately 3.5 days. The epoch is set near the center of the curve fit interval. Even if the updating period and the curve fit interval are extended, this relationship (of the epoch being set near the middle of the curve fit interval) will be maintained.
(4) ott : UTC parameter epoch The minimum update period for UTC parameters is six days.
6.3.1.3 Consideration for Week Overlap on the Part of the User
Same as in Applicable Documents (1), (2) and (3). When implementing the user algorithms in Sections 6.3.2, 6.3.5, 6.3.6, etc., when it is necessary to determine the interval, (tinterval = t - t0), between the current time, t, and the epoch time, t0, the week beginning/end overlap should be taken into account using the following equations:
(a) When ][302400 stt o : ][604800 sttt ointerval
(b) When ][302400 stt o : ][604800 sttt ointerval
(c) At all other times: ointerval ttt
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6.3.2 User Algorithm for SV Clock Offset
In general, the SV Clock Offset algorithm is the same as in Applicable Documents (1), (2) and (3). However, the following points differ from the algorithms specified for GPS alone. The QZS orbit time is estimated and predicted using the LC pseudorange derived from the ionospheric delay-free linear combination (LC) of the L1C/A signal and the L2C signal. The estimation is referenced to the LC antenna phase center of the QZS L-band transmit antenna (L-ANT). This algorithm is used when determining the offset between (a) the LC-SV clock, tsv, estimated and predicted at the LC antenna phase center, and (b) GPST. Single- and dual-frequency-signal users should perform the SV clock corrections corresponding to each QZS signal as noted in this item and in Sections 6.3.3 and 6.3.4. The series of equations in (1) and (2) below are simultaneous equations, (i.e., to determine t, it is necessary to determine ttsv and ttr using t). However, the values are less than 1 ms, so the
sensitivity of ttsv and ttr with respect to t can be ignored.
ttttttttt rcsvsvsv where
t: GPST ttsv : Estimated time when the QZS signal was transmitted from the LC antenna phase
center ttsv : ttsv time offset with respect to GPST
ttc : ttsv time offset of the onboard clock with respect to GPST
ttr : ttsv time offset (due only to relativistic effects) with respect to GPST
(1) LC-SV Clock Offset at LC Antenna Phase Center
The time offset ttc of ttsv with respect to GPST, not including relativistic effects, is expressed as follows:
2210 ocfocffc ttattaatt
where
t: GPST
oct : Epoch of SV clock parameter. This is provided in Subframe 1 in the case of the L1C/A signal, in Message Types 30, 31, 32, 33, 34, 35 and 37 in the case of the L2C and L5 signals, and in Subframe 2 in the case of the L1C signal.
210 ,, fff aaa : SV clock parameters. These are provided in Subframe 1 in the case of the L1C/A signal, in Message Types 30, 31, 32, 33, 34, 35, and 37 in the case of the L2C and L5 signals, and in Subframe 2 in the case of the L1C signal.
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(2) Relativistic Effect Correction at LC-SV Clock Offset
The time offset ttr of ttsv with respect to GPST due to the relativistic effect is expressed as follows:
2
2sinc
tVtPtEAFett kr
where
2
2c
F
: Constant, determined from the constants shown in Section 6.1.1 and Section 6.1.2.
Ae, : Provided in Subframes 2 and 3 in the case of the L1C/A signal, in Message Types 10 and 11 in the case of the L2C and L5 signals, and in Subframe 2 in the case of the L1C signal.
tEk : Eccentric anomaly at t on the GPST time scale. Determined in accordance with Section 6.3.5.
tVtP , : QZS position and velocity at t on the GPST time scale. Determined in accordance with Section 6.3.5. This is the same value for both the coordinate system in Section 6.2.2.1 and the geocentric inertial coordinate system.
6.3.3 Ionospheric Delay Correction for Dual Frequency Users
6.3.3.1 For L1C/A and L2C Dual Frequency Users
L1C/A and L2C dual frequency users should correct the ionospheric delay using the following equation:
svGD
12
A/C1L12C2LL1C/A12L2C
12
L1C/AsvL1C/A12L2CsvL2CA/C1LC2L
tccT1
ISCISCcPRPR1
tcPRtcPRPR
A/C1LC2LPR : Pseudorange corrected using the ionospheric delay and the SV clock parameters
L2CL1C/A PRPR , : Pseudorange measured using the signal indicated by the subscript 2
120154
12 : Square of the ratio between the two signal frequencies
c: Speed of light as indicated in Section 6.1.1
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6.3.3.2 For L1C/A and L5 Dual Frequency Users
L1C/A and L5 dual frequency users should correct the ionospheric delay using the following equation:
svGD
15
L1C/A15L5I5L1C/A15L5I5
15
L1C/AsvL1C/A15L5I5svL5I5L1C/AL5I5
tccT1
ISCISCcPRPR1
tcPRtcPRPR
svGD
15
L1C/A15L5Q5L1C/A15L5Q5L1C/AL5Q5 tccT
1ISCISCcPRPR
PR
where
ACLQLACLIL PRPR /155/155 , : Pseudorange corrected using the signals indicated by the subscripts using ionospheric delay and SV clock correction parameters
55,, QLL5I5L1C/A PRPRPR : Pseudorange measured using the signal indicated by the subscript
2
115154
15 : Square of the ratio between the two signal frequencies
c : Speed of light as indicated in Section 6.1.1
6.3.3.3 L2C and L5 Dual Frequency Users
L2C and L5 dual frequency users should correct the ionospheric delay using the following equation:
svGD
25
C2L25L5I5L2C25L5I5
25
L2CsvL2C25L5I5svL5I5L2CL5I5
tccT1
ISCISCcPRPR1
tcPRtcPRPR
svGD
25
C2L25L5Q5L2C25L5Q5L2CL5Q5 tccT
1ISCISCcPRPR
PR
where
CLQLCLIL PRPR 255255 , : Pseudorange corrected using the signals indicated by the subscripts using ionospheric delay and SV clock correction parameters
55552 ,, QLILCL PRPRPR : Pseudorange measured using the signal indicated by the subscript
2
25
2
12 115120,
115154
: Square of the ratio between the two signal frequencies
c : Speed of light as indicated in Section 6.1.1
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6.3.3.4 L1C and L2C Dual Frequency Users
L1C and L2C dual frequency users should correct the ionospheric delay using the following equation.
svGD
12
L1C12C2LL1C12L2C
12
L1CsvL1C12L2CsvL2CL1CL2C
tccT1
ISCISCcPRPR1
tcPRtcPRPR
where
CLCLPR 12 : Pseudorange corrected using the signals indicated by the subscripts using ionospheric delay and SV clock correction parameters
CLCL PRPR 12 , : Pseudorange measured using the signal indicated by the subscript (L1CP signal or L1CD signal in the case of the L1C signal)
2
120154
12 : Square of the ratio between the two signal frequencies
c : Speed of light as indicated in Section 6.1.1
6.3.3.5 L1C and L5 Dual Frequency Users
L1C and L5 dual frequency users should correct the ionospheric delay using the following equation:
svGD
15
L1C15L5L1C15L5
15
L1CsvL1C15L5svL5L1CL5
tccT1
ISCISCcPRPR1
tcPRtcPRPR
CLLPR 15 : Pseudorange corrected using the signals indicated by the subscripts using ionospheric delay and SV clock correction parameters
51 , LCL PRPR : Pseudorange measured using the signal indicated by the subscript (L1CP signal or L1CD signal in the case of the L1C signal; L5I signal or L5Q signal in the case of the L5 signal)
2
115154
15 : Square of the ratio between the two frequencies
c : Speed of light as indicated in Section 6.1.1.
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6.3.4 Correction of Inter-Signal Group Delay Error by Users of Only One Signal
The inter-signal group delay error terms ( GDT , ACLISC /1 , CPLISC 1 , CDLISC 1 , CLISC 2 , 55ILISC
and 55QLISC ) are based on the relationship between the L1C/A signal and the L2C signal in accordance with the measurements of the satellite currently under consideration. These terms indicate the difference in inter-group delay error between these signals and the L1CD, L1CP, L2C, L5I and L5Q signals. The standard for svt , as shown in Section 6.3.2, is determined based on the LC estimated distance obtained through the ionospheric delay free linear combination using the L1C/A signal and the L2C signal. Accordingly, single frequency users should use the following equation to correct the value: From the definitions for svt and GDT , the values of L1C/AISC in navigation message is as follows:
0ISC A/C1L
6.3.4.1 Correction of Inter-Signal Group Delay Error for L1C/A Signal
GDsvA/C1LGDsvA/C1Lsv TtISCTtt
GDT : Provided by in Subframe 1
6.3.4.2 Correction of Inter-Signal Group Delay Error for L2C Signal
C2LGDsvC2Lsv ISCTtt
C2LGD ISC,T : Provided in Message Type 30
6.3.4.3 Correction of Inter-Signal Group Delay Error for L5 Signal
5555 ILGDsvILsv ISCTtt 5555 QLGDsvQLsv ISCTtt
GDT , 55ILISC , 55QLISC : Provided in Message Type 30
6.3.4.4 Correction of Inter-Signal Group Delay Error for L1C Signal
CP1LGDsvCP1Lsv ISCTtt
CD1LGDsvCD1Lsv ISCTtt
GDT , L1CPISC , L1CDISC : Provided in Subframe 2
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6.3.5 Calculation of Satellite Orbit using Ephemeris Data
The MCS estimates the QZS orbit in accordance with the virtual LC pseudorange obtained through ionospheric delay-free linear combination using the L1C/A signal and the L2C signal. Based on various QZS models, the MCS propagates the orbit value in its generation of navigation messages. During this process, the LC antenna phase center of the L1C/A and L2C signals is the reference for estimates, predictions and navigation messages. The algorithm for calculations of LC antenna phase center of QZS-1 calculations using Ephemeris Data is as follows:
(1) L1C/A signals Positioning Calculation algorithms with Ephemeris data of L1C/A signal is the same as in table 20-IV of Applicable document (1).
(2) L1C signals, L2C signals and L5 signals Positioning Calculation algorithms with Ephemeris data of L1C signals, L2C signals and L5 signals are the same as in table 30-II of Applicable document (1) except following point. (You should use the same value with GPS (Ex. the reference value of change rate for right
ascension of ascending node ( REF )=-2.6×10-9[semi-circles/second])). (a) The reference value of Semi-Major Axis
AREF=42164200[m]
6.3.6 Calculation of Satellite Orbit and SV Clock Offset using Almanac Data
Almanac Data can be used for the rough calculation of predictions for SV clock offset and satellite orbit. 6.3.6.1 Almanac Data
(1) L1C/A signal almanac and Midi almanac (L1C, L2C, L5) The algorithm for satellite orbit calculations using L1C/A signal Almanac Data and Midi Almanac Data are the same as the algorithm using Ephemeris Data as noted in Table 20-IV of Section 20.3.3.4.3 of Applicable Document (1), with the following exceptions: (a) Setting to Zero
All parameters present in Ephemeris Data and not present in Almanac Data should be set to "0".
(b) Calculation of orbit Inclination Angle In the case of QZSS: ][25.0 circlesemiiia
In the case of GPS: ][3.0 circlesemiiia
ia: Actual inclination value i : Inclination value included in navigation message
(c) Calculation of Eccentricity (unique to QZSS)
In the case of QZSS: ea=0.06+enav In the case of GPS: ea=0.0+enav
ea: Actual eccentricity value enav: Eccentricity value included in navigation message
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(2) Reduced almanac (L1C, L2C and L5 signals)
The algorithm for satellite orbit calculations using Reduced Almanac Data is the same as the algorithm using Ephemeris Data as noted in Table 30-II of Applicable Document (1), with the following exceptions: (a) Setting to Zero
All parameters present in Ephemeris Data and not present in Almanac Data should be set to "0".
(b) Calculation of Semi-Major Axis
For QZSS: A[m] 42,164,200 A For GPS: A[m] ,559,71026 A A : Semi-Major Axis value included in navigation message
(c) Eccentricity For QZSS: ea = 0.075 [-] For GPS: ea = 0.0 [-] ea: Actual eccentricity value
(d) Orbit Inclination Angle For QZSS: ia = 43 [deg] (= 0.2389 [semi-circles]) For GPS: ia = 55 [deg] (= 0.3056 [semi-circles]) ia: Actual Inclination Angle
(e) Change rate in Right ascension of ascending node (RAAN)
For QZSS: conds]circles/se-[semi 107.8 10
For GPS: conds]circles/se-[semi 106.2 9
(f) Argument of Perigee
For QZSS: [deg] 027 (=-0.5 [semi-circles]) For GPS: [deg] 0 (= 0 [semi-circles])
(3) The satellite positioning accuracy resulting from Almanac Data The satellite positioning accuracy resulting from Almanac Data is in accordance with Applicable Document (1) in the case of GPS, and Sections 5.2.2.2.5.2 (2) (a), 5.5.2.2.4.5 and 5.5.2.2.4.6 in the case of QZSS.
6.3.6.2 Almanac Reference Time (toa) and Almanac Reference Week Number (WNa)
Note that the Almanac reference time may not be updated even if the Almanac data has been updated. The L1C/A signal differs from GPS as noted in Section 5.2.2.2.5.1 in that the concept of pages does not exist. For this reason, it is impossible to guarantee when Almanac data updating may occur. For more information on the Almanac reference Week Number corresponding to Almanac reference time, see Section 5.2.2.2.5.2(5).
6.3.6.3 Calculation of Satellite SV Clock Offset using Almanac Time Data
Almanac time data can be used for the rough calculation of prediction of the SV clock offset. The reduced Almanac is not included in the Almanac time data. Of these, the Almanac time data comprise an 11-bit constant (af0) and an 11-bit (10-bit for the CNAV and CNAV2 message) primary term (af1). These data can be used to determine the satellite time offset with respect to GPS time. The algorithm used to calculate the SV clock offset using Almanac time data is the same as the algorithm using Ephemeris data specified in Section 6.3.2(1), with the following exceptions.
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(a) Setting to zero Parameter af2 that is present in Ephemeris data and not present in Almanac data should be set to "0".
The SV clock offset accuracy produced by Almanac data is in accordance with Applicable Document (1) in the case of GPS and Section 5.2.2.2.5.2 (2) (a) in the case of QZSS.
6.3.7 Calculation of Coordinated Universal Time (UTC) using the global standard time
parameter
It is possible to use the UTC parameter to convert system time to coordinated universal time (UTC). In the case of the L1C/A signal, coordinated universal time is UTC (USNO) when the data ID is "00" and UTC (NICT) when the data ID is "11". In the case of the L2C and L5 signals, coordinated universal time is UTC (USNO) in the case of Message Type 49 and UTC (NICT) in the case of Message Type 33. The algorithm is the same as in Section 20.3.3.5.2.4 of Applicable Document (1).
6.3.8 Correction of Ionospheric Delay Using Ionospheric Parameters
This is the same as in Section 20.3.3.5.2.5 of Applicable Document (1). Correction can be performed by determining the ionospheric delay, ionocT , for the L1 frequency and subtracting this value from measured pseudorange.
The ionospheric delay for the L2 frequency is ionoTc2
120154
. The ionospheric delay for the LEX
frequency is ionoTc2
125154
. The ionospheric delay for the L5 frequency is ionoTc2
115154
.
6.3.9 Correction Using NMCT (L1C/A Signal) and DC Data (L1C, L2C and L5 Signals)
6.3.9.1 Correction Using NMCT (Navigation Message Correction Table) Data
For the L1C/A signal, the Estimated Range Deviation (ERD) value in the NMCT for each satellite is the estimate of the difference between (a) the measured pseudorange value for each satellite monitored from the ground by QZSS and (b) the value for pseudorange that is calculated based on the Ephemeris data and SV clock parameters for each satellite tracked. ERD is calculated by the MCS. The following equation is used to correct the measured pseudorange value using the ERD value:
ERDPRPR MC where
CPR : Corrected pseudorange value ERD: Estimated range deviation
MPR : Measured pseudorange value
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6.3.9.2 Correction using DC Data (L1C, L2C and L5 Signals)
In the L1C, L2C and L5 signals, the DC data for each satellite constitute the estimate of the difference between (a) the measured pseudorange value for each satellite monitored from the ground by the QZSS MCS and (b) the value for estimated pseudorange that is calculated based on the Ephemeris data and SV clock parameters for each satellite tracked. The DC data are calculated by the MCS. 6.3.9.2.1 Use of CDC Data
If the satellite DC data pair (EDC and CDC) can be used, the user may use the CDC data in place of the algorithm in Section 6.3.2 (1) to perform the LC-SV clock correction referenced to the LC antenna phase center. In other words, the PRN code phase offset ttc of the satellite time with respect to QZSST, with the exception of the relativistic effect, is expressed as follows:
221100 ocfocffffc ttattaaaatt
where
t : QZSST defined in Section 3.1.4.1
oct : Epoch of SV clock parameter, provided in Subframe 1 in the case of the L1C/A signal, in Message Types 30, 31, 32, 33, 34, 35 and 37 in the case of the L2C and L5 signals, and in Subframe 2 in the case of the L1C signal.
210 ,, fff aaa : SV clock parameters, provided in Subframe 1 in the case of the L1C/A signal, in Message Types 30, 31, 32, 33, 34, 35 and 37 in the case of the L2C and L5 signals, and in Subframe 2 in the case of the L1C signal.
10 , ff aa : SV clock parameters, provided in Message Types 34 and 13 in the case of the L2C and L5 signals, and in Subframe 3 in the case of the L1C signal. This can only be applied when predict time of week for the Ephemeris Data and the SV Clock Parameters is older than predict time of week of the DC data (in other words, when the value of Dopt is
greater than the value of opt ).
6.3.9.2.2 Use of EDC Data
If the satellite DC data pair (EDC and CDC) can be used, the user may use the EDC data in place of the algorithm in Section 6.3.5 to calculate the orbit referenced to the LC antenna phase center. This user algorithm is the same as the one in Applicable Document (1). This can only be used when the epoch for the Ephemeris data and the SV clock parameters is older than the epoch of the DC data (in other words, when the value of Dopt is greater than the
value of opt ).
6.3.10 User Algorithms Relating to Interoperability with Other Satellite Navigation Systems
TBD
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6.4 L1 SAIF Algorithm
6.4.1 Validity period (Time-out period)
User receivers must keep track of the age-of-data corresponding to each L1-SAIF message parameter. The contents of the SAIF messages have various validity periods so-called “time-out period” appropriate to the characteristics of each parameter as shown in Table 6.4.1-1. Any SAIF parameters whose age-of-data exceeds the corresponding validity period must not be used for navigation. The starting point for determination of the age-of-data is the second of the GPS epoch time when the first bit of the preamble for the message including a relevant parameter is transmitted. The validity period is defined in Table 6.4.1-1. Note that the durations of the validity periods not only vary from message type to message type, they also can be different for different parameters within the same message type. In particular, Message types 2-6 and 24 include both the Fast Correction parameter (FCi) and its accuracy (UDREIi), and these two parameters have different validity periods.
Table 6.4.1-1 Validity Periods for L1-SAIF Message Parameters Message Type ID Contents Timeout period (s)
0 Test mode 60 1 PRN mask 1200
2 – 6, 24 Fast Correction 120 UDREI 12
10 Degradation Parameter 240 18 IGP mask 1200
24, 25 Long-term Correction 240 26 Ionospheric Vertical Delay 600
GIVEI 600 28 Clock-ephemeris Covariance 240 52 TGP mask 600 53 Tropospheric Delay Correction 600 56 Inter signal bias correction data 1200 58 QZS ephemeris 300
6.4.2 Error Correction Algorithm
6.4.2.1 Clock and Orbit error correction (Long-term correction)
The Long-term correction message (Message type 24, 25) provides parameters for use in correcting both clock and orbital position errors associated with the corresponding navigation satellite. The clock offset value calculated using the navigation messages transmitted by each GPS or QZS is further corrected as follows using the long-term Clock Error Correction parameter in the SAIF message.
iSViSVcorrected
iSV ttt ,,, (6.4-1) where,
iSVt , [s] is the Clock Error Correction parameter of the Long-term Correction SAIF message. In addition, the orbital position of the corresponding navigation satellite is corrected as follows using the long-term Orbital Position correction parameters in SAIF message as well.
i
i
i
ephemerisi
i
i
correctedi
i
i
zyx
zyx
zyx
(6.4-2)
where, δxi, δyi and δzi [m] are respectively, the x-, y- and z- Orbital Position Error Correction parameters of the Long-term Correction SAIF message. The satellite clock error correction parameter, δΔtsv,i, at any time of day, tk, is calculated using the following equation. (This parameter is applied to the clock offset calculation in accordance with
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equation (6.4-1).)
LTikfifikiSV ttaatt ,1,0,, (6.4-3) where LTik tt , is corrected for end of day crossover if necessary. If the velocity code = 0, then the corresponding δai,f1 term should be set to 0. In cases where the augmented navigation satellite signals are from a different RNSS system, for instance GLONASS, the following equation is to be applied:
GLONASSiLTikfifikiSV attaatt ,,1,0,, (6.4-4) In this case, the time offset between GPS time and GLONASS, δai,GLONASS, is provided in message type XXX (TBD). Users must NOT use GLONASS unless the corresponding time offset parameter is received. The appropriate correction value from equation (6.4-3) or (6.4-4) is added to the estimated time, Δtsv, defined in Applicable Document (1). The orbital position of the corresponding navigation satellite is corrected by adding the correction vector calculated in equation (6.4-5) to the estimated position vector (see equation (6.4-2)) received via the broadcast ephemeris data.
LTik
i
i
i
i
i
i
i
i
i
ttzyx
zyx
zyx
,
(6.4-5)
The above correction vector is applied to the same satellite, i, in ECEF coordinates at time, tk. If the velocity code = 0, then the second term in equation (6.4-5) should be set to 0. Note that the ephemeris data broadcast in the L1-C/A signal, (i.e., NAV message), MUST be used for the corrections calculated in equations (6.4-1) and (6.4-2) using data from the L1-SAIF messages. Ephemeris data provided in the CNAV or CNAV2 messages should NOT be applied to the corrections performed using the L1-SAIF message data.
6.4.2.2 Fast Correction and Atmospheric Delay Correction
The error correction parameters broadcast in the SAIF messages are used to correct the pseudorange measurements (between satellite and user receiver). The corrected pseudorange, corrected
iPR [m], is used to compute user position after the SAIF correction parameters are applied to the measured pseudorange for each observable satellite, measured
iPR [m] using the following equation:
iiimeasuredi
correctedi TCICFCPRPR (6.4-6)
FCi, ICi, and TCi [m] are the Fast Correction, Ionospheric Delay Correction, and Atmospheric Delay Correction parameters, respectively. In advance of applying the ionospheric and atmospheric delay corrections, a rough estimate of user position is required since these delay corrections are dependant upon position. The Fast Correction parameter is mainly used for the correction of satellite onboard clock variation. It can be used to correct clock variations ranging from several seconds to several minutes. The Fast Correction parameter is not a function of user position and its value at any given time will be identical for all users. Note that the ionospheric and atmospheric delay correction parameters are not frequently updated. For a general least-squares position solution, the following projection matrix, S, is used:
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WGGWG
ssssssssssss
S
Nttt
Nzzz
Nyyy
Nxxx
T1T
,2,1,
,2,1,
,2,1,
,2,1,
(6.4-7)
where, G is the matrix which represents the relationship between user position and satellite position:
1sincoscossincos
1sincoscossincos1sincoscossincos
22222
11111
NNNNN ELAZELAZEL
ELAZELAZELELAZELAZEL
G
(6.4-8)
where ELi [rad] and AZi [rad] are the calculated elevation angle and azimuth, respectively, from the user to satellite i. AZi is the azimuth angle of the satellite measured from North in a clockwise direction. The inverse of the weighting matrix, W, is expressed as below:
2
22
21
1
00
0000
N
W
(6.4-9)
where i is the calculated user range error with respect to satellite i.
6.4.2.3 Ionospheric Propagation Delay Correction
6.4.2.3.1 Determination of Pierce Point
In order to calculate an ionospheric delay correction, the ionospheric pierce point (IPP), must first be determined. The IPP is defined as the point (in the ionospheric layer) where the line between a satellite and the user receiver intersects the ellipsoidal surface 350 km above the WGS84 ellipsoidal surface. Firstly, the latitude, ipp, [rad], of the IPP is calculated using following equation:
iippuippu-
ipp AZcossincoscossinsin ,,1
, (6.4-10) where, u [rad] is the latitude of the user receiver, and ipp, [rad] is the angle: IPP - Earth center - user position, calculated as follows:
iIe
eiipp EL
hRRELπ cossin
21
, (6.4-11)
where ELi [rad] is the elevation angle of satellite; Re [km] is the Earth’s radius; and hI is the approximate altitude of ionospheric layer, assumed to be 350 [km]. Next, the longitude, ipp, [rad], of the IPP is calculated using one of the following equations:
AZλλ
ipp
iipp-uipp
,
,1, cos
sinsinsin
(6.4-12)
where u [rad] is the longitude of the user receiver and the other terms are as defined above.
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6.4.2.3.2 Selection of Ionospheric Grid Points (IGP)
The ionospheric delay at an IPP is calculated by interpolation using the ionospheric delay values at surrounding IGPs. The IGPs are selected in accordance with the IGP mask information provided in message type 18, independent of the value of delay and GIVE at each IGP. The selection of the IGPs is implemented with one of the following two procedures: Procedure a): If an IPP is surrounded by four IGPs arranged in a rectangular shape separated by 5 degrees in both latitude and longitude, these surrounding four IGPs are selected for the ionospheric delay correction. Procedure b): If an IPP is not surrounded by four IGPs as defined in Procedure a), but is surrounded by three IGPs arranged in a triangular shape separated by 5 degrees in both latitude and longitude, these surrounding three IGPs are selected for the ionospheric delay correction. In cases where an IPP is not surrounded by four or three IGPs, as required for Procedure a) or b), respectively, the ionospheric delay for that IPP cannot be calculated. Moreover, if any one of the IGPs selected for Procedure a) or b) above is prohibited from use or unmonitored, the ionospheric delay at the corresponding IPP cannot be computed. However, in the case of Procedure a), if only one of the four surrounding IGPs is prohibited from use, then the remaining three valid IGPs can be used with Procedure b).
6.4.2.3.3 Ionospheric Delay Interpolation at Pierce Point
The ionospheric delay at the IPP is calculated by interpolation using the delays associated with the four or three IGPs selected using Procedure a) or b), respectively, as described in the previous section. The following equation is to be used for interpolation with four IGPs:
4
1,,, ,
kkkippippipp W (6.4-13)
The vertical delay at the IPP, ipp, [s], is described as a function of the IPP latitude, ipp, [rad],
and the IPP longitude, ipp, [rad]. k [s] is the vertical delay at IGP k.
The weighting coefficient at each IGP is computed using 12
1,
12
1, ,
ipp pp
ipppp y
λλx as
follows:
pppp yxW 1 (6.4-14)
pppp yx(W )12 (6.4-15)
)y)(x(W pppp 113 (6.4-16)
)y(xW pppp 14 (6.4-17) The following definitions illustrated in Figure 6.4.2-1 also apply: λ1 [rad] = longitude of IGPs west of IPP λ2 [rad] = longitude of IGPs east of IPP φ1 [rad] = latitude of IGPs south of IPP φ2 [rad] = latitude of IGPs north of IPP
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φ 1
φ 2
λ 1 λ 2
x
y
Δ φ pp=φ pp,i-φ 1
Δ λ pp=λ pp,i-λ 1
τ pp,i(φ pp,i ,λ pp,i)
τ 1τ 2
τ 4τ 3
User’s IPP
φ 1
φ 2
λ 1 λ 2
x
y
Δ φ pp=φ pp,i-φ 1
Δ λ pp=λ pp,i-λ 1
τ pp,i(φ pp,i ,λ pp,i)
τ 1τ 2
τ 4τ 3
User’s IPP
Figure 6.4.2-1 Definition of interpolation with four surrounding IGPs
The following equation is to be used for interpolation with three IGPs:
3
1,,, ,
kkkippippipp W (6.4-18)
The weighting coefficient for each IGP is as follows:
ppyW 1 (6.4-19)
pppp yxW 12 (6.4-20)
ppxW 3 (6.4-21) As illustrated in Fig. 6.4.2-2, the second weighting coefficient, W2, must be properly determined from the three IGPs.
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φ 1
φ 2
λ 1 λ 2
x
y
Δ φ pp=φ pp,i-φ 1
Δ λ pp=λ pp,i-λ 1
τ 1
τ 2 τ 3
τ pp,i(φ pp,i ,λ pp,i)User’s IPP
φ 1
φ 2
λ 1 λ 2
x
y
Δ φ pp=φ pp,i-φ 1
Δ λ pp=λ pp,i-λ 1
τ 1
τ 2 τ 3
τ pp,i(φ pp,i ,λ pp,i)User’s IPP
Figure 6.4.2-2 Definition of interpolation with three surrounding IGPs
6.4.2.3.4 Computation of Ionospheric Propagation Delay Correction
The slant delay correction value, ICi, is calculated by multiplying the vertical delay at the IPP (as interpolated from the surrounding IGPs), by the obliquity factor, Fpp.
ippippippippi λτFIC ,,,, , (6.4-22) where,
21
2
,cos1
Ie
ieipp hR
ELRF (6.4-23)
is the obliquity factor which depends upon the elevation angle from the user receiver to the satellite, ELi [rad], the Earth radius Re = 6378.137 [km], and the assumed altitude of the ionospheric layer hI = 350 [km].
6.4.2.4 Zenith Tropospheric Delay Correction
6.4.2.4.1 Correction based on SAIF Message
The message type 53 with TGP block ID n contains ZTDOs at from 34n+1 th to 34(n+1) th TGPs in the same order as in the effective TGP mask data provided by message type 52. 6 bits ZTDO has a resolution of 0.01m in the range of [-0.32, 0.30m]. “011111” indicates that ZTDO has not been provided at the corresponding TGP.
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By adding the value of Zenith Tropospheric Delay model defined by the following equation4 at user position to ZTDO at TGP, Zenith Tropospheric Delay at user position will be obtained. Note: Units: mm, Day of Year: doy , Latitude: [deg], Height above Sea Level: H [m]
2 4[ ] 2690 97sin 119 28sin 11 6.5365.25 365.25
2 40.31 0.023sin 63 0.0071sin 13365.25 365.25
ZTD mm doy doy
H doy doy
(6.4-24) It is recommended to use ZTDO at a TGP which is within 70km in distance from user. In the case that plural TGPs are available within this range, it is recommended to use the ZTDOs at up to 3 nearest TGPs. From the plural ZTDOs at the plural TGPs, it is possible to obtain one Zenith Tropospheric Delay more suitable for each user position through some interpolation, such as weighted average, etc. As for the weighting function, the following one could be suggested, where x [km] is a distance from TGP.
21 0.08 10.0w x x (6.4-25)
Tropospheric Delay contained in pseudorange is estimated by multiplying Zenith Tropospheric Delay and mapping function. Additive inverse of the obtained Zenith Tropospheric Delay is equivalent to iTC in equation (6.4-6). As for the mapping function, the following equation could be suggested as an example, where EL [rad] is the elevation of satellites.
EL
ELm2sin002001.0
001.1
(6.4-26)
iTC in equation (6.4-6) is computed as follows:
nT
kk
nT
kkk
ii
xw
ZTDxwELmTC
1
1
)(
)((
・
)・ (6.4-27)
Where nT is the number of TGPs for tropospheric correction.
6.4.2.4.2 Correction by the model
Tropospheric delay correction may be performed by the model described in Application document (5).
4 There will be possibility to change about detailed numerical value in future.
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6.4.3 Algorithm for Integrity information
Integrity of SAIF message is actually depending on the protection level. It means that the probability which user positioning error of horizontal and vertical direction is beyond the protection level shall be specified integrity risk (1 - integrity) or less to (in) the SIS accuracy that has provided by SAIF message with the signal.
6.4.3.1 Calculation of protection level
Horizontal Protection Level(HPL) and Vertical Protection Level(VPL) is calculated as follows.
HH dKHPL (6.4-27)
VV dKVPL (6.4-28) Constants are defined by Table 6.4.3-1. “Integrity” in the table means integrity required by the user. IRI is broadcasting via message type 10. See the covariance of positioning error as follows.
N
iiizV sd
1
22,
2 (6.4-29)
2
222222
22 xyyxyx
H ddddd
d
(6.4-30)
Calculate the each with the following value.
N
iiixx sd
1
22,
2 (6.4-31)
N
iiiyy sd
1
22,
2 (6.4-32)
N
iiiyixxy ssd
1
2,, (6.4-33)
Positioning accuracy i as for Satellite i is determined as follows.
2,
2,
2,
2,
2tropiairiUIREifltii (6.4-34)
Table 6.4.3-1 Relations of integrity and Constants “K” integrity IRI condition KH KV
1-10-7 IRI=0 5.63 5.33
1-10-6 IRI≦1 5.26 4.90
1-10-5 IRI≦2 4.80 4.42
1-10-4 IRI≦3 4.29 3.89
1-10-3 IRI≦4 3.72 3.29
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6.4.3.2 Clock and orbit configuration
Correction accuracy of fast and long-term correction is calculated as follow.
1,0,
222,
2,2
,UDREltcUDREUDREi
UDREltcUDREUDREiflti RSS
RSS
(6.4-35)
As for the long correction degradation, GPS and Geostationary satellite is determined as below. Note that VC is the velocity code contained long-term correction data.
0,
1,,,0max
0_0_
1_,,1__
VCI
ttC
VCIttttCC
vltc
ltcvltc
vltcLTiLTivltclsbltc
ltc (6.4-36)
Also, QZSS is calculated as follows.
1_,,1__ ,,0max vqzsLTiLTivqzslsbqzsltc IttttCC (6.4-37)
6.4.3.3 Clock―ephemeris covariance
Message type 10 and 28 is calculated by equation(6.4-35)の UDRE
arianceTTe
UDRE CIEEI cov52 (6.4-38)
Note: “e” is scale coefficient shown in the message type 28. “I” is the vector which contains unit vector that indicates the direction of satellite from receiver.
1sin
coscossincos
i
ii
ii
ELAZELAZEL
I (6.4-39)
Matrix E is as follows
4,4
4,33,3
4,23,22,2
4,13,12,11,1
00000
0
EEEEEEEEEE
E (6.4-40)
6.4.3.4 Ionospheric Propagation Delay
σ2UIRE of equation(6.4-34) is calculated as follows.
UIVEppUIRE F 222 (6.4-41)
σ2
UIVE is interpolated to the specified IPP with σ2GIVE defined at IGPs by user as follows.
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GIVEnppppn
nUIVE ,yxW ,2
4
1
2 )(
(6.4-42)
or
GIVEnppppn
nUIVE ,yxW ,2
3
1
2 )(
(6.4-43)
Note: σ2
GIVE is the dispersion model of Ionospheric vertical delay error at IGP. It can be obtained by GIVEI on table 5.4.3-16.
6.4.3.5 Multipath error
As for airi , that shows multipath error, use the following model.
22, 4.0deg10exp53.013.0 iairi EL (6.4-44)
6.4.3.6 Tropospheric Propagation Delay
Remained error model of Tropospheric Delay of Satellite i is calculated as follows.
i
tropiEL2,
sin002.012.0
(6.4-45)
6.4.4 Calculation of QZSS satellite Position
The position of QZSS satellite can be calculated by numerical integration with position and velocity given in message type 58. Satellite position is calculated using following equations.
xvdtdx
(6.4-46)
yvdtdy
(6.4-47)
zvdtdz
(6.4-48)
According to the velocity, following equations with perturbation of the acceleration given in message type 58 can be used.
Qyeeex Xvxx
rz
rRJ
rx
dtdv
251
23 2
2
2
5
2
23
(6.4-49)
Qxeeey Yvyy
rz
rRJ
ry
dtdv
251
23 2
2
2
5
2
23
(6.4-50)
Qez Zz
rz
rR
Jrz
dtdv
2
2
5
2
23
5323
(6.4-51)
Here, 9
2 107.1082625 J
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6.5 LEX Algorithm
6.5.1 Reed Solomon Coding/Decoding Algorithm for LEX Navigation Message
6.5.1.1 Construct Galois Field 82GF
We choose 1278 xxxxxF as a primitive polynomial of degree 8 over 2Z . (Note that because this is the binary case, addition (+) is equivalent to exclusive-OR (XOR) and multiplication (x) is equivalent to the logical AND operation.) When is a root of 0xF , we have the following (note that 88 over 2Z ):
12788 (6.5-1) From equation (6.5-1), any power of can be represented by a linear combination of
1,,,,,,, 01234567 over 2Z (note that 0 ii )as follows:
1
11
11
1
67254
247
42748910
37
232723889
278
(6.5-2)
Then, the order of is 255 since:
02727278254255 11 (6.5-3) From equations (6.5-2), addition of two powers of is as follows: When
00
11
66
77 mmmm
m uuuu (6.5-4)
00
11
66
77 nnnn
n uuuu (6.5-5)
the addition is given by:
l
nmnmnmnmnm uuuuuuuu
000
111
666
777 (6.5-6)
Each njmi uu , coefficient is either a zero or a one, and nimi uu is the logical “exclusive OR” of
the two coefficients. By the above operations, 254210 ,,,,1,0 makes a Galois Field
82GF .
6.5.1.2 Change of Basis
From equations (6.5-2), one basis for 254210 ,,,,1,0 over 2Z is the set
01234567 ,,,,,,, .
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When 2427
676
1845
464
1633
2262
881
1250 ,,,,,,, llllllll ,
the set 76543210 ,,,,,,, llllllll is another basis for 254210 ,,,,1,0 over 2Z . When the nth power of is represented by two linear combinations:
7766554433221100
00
11
22
33
44
55
66
77
lzlzlzlzlzlzlzlzuuuuuuuun
(6.5-7)
The relationship between 01234567 ,,,,,,, uuuuuuuu and
76543210 ,,,,,,, zzzzzzzz is given by the following two equations:
1101111110010101
1110010110011111
0110001111111011
0001011101110001
,,,,,,,
0
1
2
3
4
5
6
7
76543210
t
uuuuuuuu
zzzzzzzz (6.5-8)
0011001110010000
0011010111101111
1011011101001010
1111010000100011
,,,,,,,
7
6
5
4
3
2
1
0
01234567
t
zzzzzzzz
uuuuuuuu (6.5-9)
Each ji zu , coefficient is either a zero or a one, and addition for these matrix operations is simply “exclusive OR”.
6.5.1.3 Encoding
When the Header and Data parts of the LEX message (see Figure 5.7.2-1) are given, the Reed-Solomon encoding is performed as follows. The target encoded length is 214 symbols (5 to 218) followed by the Preamble. Think of the bits in each symbol as 76543210 ,,,,,,, zzzzzzzz , corresponding to the elements of
254210 ,,,,1,0 (see Section 6.5.1.2). When the binary string 5th,6th,・・・,218th
symbol is represented by 5A , 6A ,・・・ , 218A ( 254210 ,,,,1,0 iA ), polynomial
xI over 254210 ,,,,1,0 is defined as follows:
218217212
6213
5 AxAxAxAxI (6.5-10)
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If the code generator polynomial over 254210 ,,,,1,0 is defined as follows:
143
112
11
j
jxxg (6.5-11)
then, xP is the remainder of dividing xIx32 by xg . Division is used operation of Galois
Field 254210 ,,,,1,0 (see Section 6.5.1.1).
xP is written as follows:
323130
231
1 BxBxBxBxP (6.5-12)
254210 ,,,,1,0 iB When each iB is represented by a linear combination of set 76543210 ,,,,,,, llllllll :
7766554433221100 lzlzlzlzlzlzlzlzBi (6.5-13)
The 32-symbol Reed-Solomon Code is generated by thinking of 76543210 ,,,,,,, zzzzzzzz as the bits of the symbol.
6.5.1.4 Decoding
Similarly, in Section 6.5.1.3, the polynomial xS is generated as follows from the 5th to 250th symbols of the received message.
250249244
6245
5 AxAxAxAxS (6.5-14)
Thus, by employing this R-S encoding/decoding we can detect errors and correct them up until 16 symbol errors occur, by computing 32 polynomials 143112,11 ~jS j . If no errors exist,
jS 11 is all zeroes.
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6.6 Other Information
6.6.1 Instrumental Bias in Receivers
It is noted that instrumental bias in receivers should be measured to correct them before shipments. Navigation results using a combination of various frequency signals may have bias without these corrections.
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7 Provision of QZSS Operational Information and Data via the Internet
QZSS operational information and data generated and accumulated data at the MCS will be provided to
users via the Internet as specified below.
7.1 QZSS Website for Operational Information and Data Users can access QZSS operational information and data at the following website (“QZ-vision”). This QZSS user website has two language choices, Japanese and English for the international user community. Japanese and English URL: http://qz-vision.jaxa.jp// (Available in the summer of 2010)
7.2 Release of QZSS Information and Data
Table 7.2-1 summarizes the QZSS operational information and that will be made publically available, and how users can access this information.
Table 7.2-1 Provision of QZSS Information and Data Category Operational Information & Data Users Access
1 Notification Advisory to QZSS Users (NAQU)
Announcements regarding interruption or degradation periods, (because of the satellite maintenance schedule Orbit Maintenance or Momentum Management)) constellation status and malfunction reports for QZSS. (Similar to NANU for GPS)
On website Distribution by e-mail if requested by users. (Requires E-mail address registration)
2 Experimental Schedule (For Step 1: Demonstration phase)
Announcement of test and experiment schedule for users. On website
3 Evaluation Result for System Performances
URE information, etc. On website
4 User Operation Support Tool
Freeware, supporting several user activities such as QZSS & GPS orbit prediction
Download from the website a free User Operation Support Tool that can be run on a user’s PC.
Latest almanac, ephemeris data Download from the website(text file)
Navigation pattern table On website
5 Precise Orbit & Clock “Ultra Rapid” and “Final” Products for both QZSS and GPS Download from the website(text file)
6 Detailed Information for Precise Satellite Orbit & Clock Estimation
Contact Point for researchers will be provided on the website.
How to request detailed information, including a contact point, will be described on the website. The requested will be provided by electronic media.
7.2.1 NAQU (NOTICE ADVISORY TO QZSS USERS)
NAQU is the QZSS version of NANU(NOTICE ADVISORY TO NAVSTAR USERS provided by the United State Coast Guard Navigation Center for GPS users). The QZSS NAQU service will be provided by JAXA via the QZSS website to inform QZSS users of operational status and planned interruption or degradation of positioning service (because of the satellite maintenance schedule (Orbit Maintenance or Momentum Management)), NAQU will also be used to announce unintentional interruptions or degradation (due to malfunctions or other reasons). The latest NAQU and several previous NAQUs are provided on the website. Moreover, for QZSS users who register their e-mail address, the latest NAQU will be sent by e-mail whenever it is posted to the website.
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7.2.2 Experimental Schedule
As for the technical validation and demonstration of application during phase I, experiments using the LEX signal and L1-SAIF signal will be scheduled and notified to users. Because the LEX signal and L1-SAIF signal messages will at times be defined by research users, it is necessary to announce the experimental schedule for this to users. In addition to the above mentioned NAQU, daily schedule (of 1 week) for planned experiments will be provided on the website indicated in Section 7.1 above.
7.2.3 Evaluation result for System Performances
The evaluation result of system performance listed in Table 7.2.3-1 is to be provided as on the website indicated in Section 7.1 above.
Table 7.2.3-1 Test Evaluation Public Release Data List No. Data Frequency of Update 1 URE information etc. Monthly
7.2.4 User Operation Support Tool
Freeware supporting several user activities such as QZSS & GPS orbit prediction, DOP profile, generation of assist data, schedule planning, etc., will be provided via the website indicated in Section 7.1 above. 7.2.4.1 User Operation Support Tool (QZ-radar)
Users can download the free software, User Operation Support Tool (UOST) as well as the associated user’s manual from the website. UOST provides the following functions:
(1) Accept input of user’s location and mask information
(2) Accept input of epoch, simulation time and orbit parameters such as Ephemeris Data and
Almanac Data
(3) Calculate GPS and QZSS position, visible satellites, Doppler frequencies, DOP, etc.
(4) Output CSV data files
(5) Produce plots and graph resulting from the above calculations
7.2.4.2 Provision of Latest Orbital Information
Via the website, users can download the latest Almanac Data and Ephemeris Data broadcast by QZSS and GPS.
(1) Almanac Data The Almanac Data can be downloaded for all satellites (QZSS and GPS) as well as past archived data. The data format is YUMA*. * YUMA: Refer to the Website of “United State Coast Guard” URL: www.navcen.uscg.gov/?pageName=gpsYuma (14 Jan., 2011)
(2) Ephemeris Data The Ephemeris Data can be downloaded for all satellites (QZSS and GPS) as well as past archived data. The data format is the same as ephemeris information of RINEX format.
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The Ephemeris Data on the website is updated according to the update of broadcast Ephemeris Data from satellites. Ephemeris Data of GPS is the data extracted from GPS navigation message received at the Monitor Station.
7.2.4.3 Provision of navigation pattern table
We have made tables of broadcasting order of the data included in each signal (L1C/A, L1C, L2C, L5, LEX) composed of subframes, pages, and messages. We call the tables "Navigation pattern table", and we have made them for every signal. We will provide the "navigation pattern table" for L1C/A signal, L1C signal , L2C signal, L5 signal and LEX signal (for JAXA's experiment only) on the website indicated in Section 7.1 above.
7.2.5 Provision of Precise Orbit & Clock for QZSS and GPS
Users can download the following precise orbit and clock data generated at MCS which are useful for scientific use, performance evaluation and Precise Point Positioning (PPP). Clock data are generated based on the QZSST not on GPS time. 7.2.5.1 “Final” Satellite Ephemerides and Clocks
The MCS generates the “Final” Satellite Ephemerides and Clocks for all GPS and QZSS satellites for 24 hours with three days latency. The format is the same as the “Final” Satellite Ephemerides and Clocks of the International GNSS Service (IGS) (SP3 format).
7.2.5.2 “Ultra-Rapid” Ephemerides and Clocks
The MCS generates broadcast Ephemeris Data from the estimated and propagated satellite position. The estimated and propagated orbit positions without fitting to broadcast ephemeris parameters can be downloaded with the same format as IGS “Ultra Rapid” ephemerides for QZSS (SP3 format). Users can download the set for old GPS as well. GPS “Ultra Rapid” ephemerides provided by the MCS doesn’t include prediction, but only estimated.
7.2.6 Detailed Information for Precise Orbit & Clock Estimation for research purposes
Upon request, users of QZSS information for research purposes will be provided operational information and data for precise QZSS orbit & clock estimation by electronic file or media (if it is a large volume). On the website you can see the contact point for the request. Since the information is provided by an off-line process by the operator, it may take about one week for users to obtain.
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8 Differences with GPS
8.1 Differences in Navigation Messages The QZSS Navigation Messages for each signal (number of bits, scale factor, parameter range, units) are designed to preserve interoperability with GPS to the greatest extent possible. However, based on differences in the conditions unique to GPS and QZSS (QZS satellite orbit conditions, etc.), in some cases QZSS Navigation Messages cannot be expressed using the same definitions as those for GPS. Moreover, in order to provide QZSS with added value not present in GPS, some content has been intentionally defined differently from GPS. For this content, the unique QZSS definitions provided below must be used. Table shows the parameters that have unique QZSS definitions. 8.1.1 Differences with GPS in terms of L1C/A signal
Table 8.1.1-1 Parameters with definitions unique to QZSS
Subframe Page Parameter GPS definition QZSS definition
All All Anti-Spoof flag P code encryption flag Not applicable since there is no P code. AS flag always set to “0”.
1 -
C/A or P on L2 L2 code identification (C/A or P) “10” fixed
L2P data flag P code message (Y/N) Not applicable since there is no P code
TGD LCGPS*2 and L1P (Y) group
delay LCQZSS*3 and L1C/A group delay
IODC The issue number of the data set, Clock
The issue number of the data set, Clock Unlike GPS's IODC, 2bits (MSB) of IODC in QZSS signals are used as counter for SV clock parameter
2 -
Ephemeris eccentricity
Parameter range is restricted (max. 0.03)
Parameter range is not restricted (max. 0.499 ---)
Curve Fit Interval 4 hours 2 hours
4
13 NMCT ERD
ERD for SV1-31 except for the SV itself transmitting that signal
Not only GPS ERD (See Table 5.2.2-3) (User algorithm for NMCT is different from GPS (See section 5.2.2.2.4 (1))
18 UTC parameter A0, A1
UTC (USNO)-GPST relationship UTC (NICT)-GPST relationship
25 A-S flag, SV conditions
P code encryption flag and SV block identification for all GPS
Not applicable since there is no P code
4, 5
Subframe 4 2 - 5 7 - 10 Subframe 5 1 – 24
DATA ID Fixed at "01" "00": GPS Almanac "11": QZS Almanac "01","10": Reserved
Almanac eccentricity*1
The eccentricity value itself Max. 0.03
Difference with QZS eccentricity 0.06
The difference from Almanac reference Inclination (i0)*1
The inclination value referenced by 0.3 [semi-circles].
Difference with QZS inclination 0.25 [semi-circles].
25 SV health Health judged by positioning signal output level
Health judged by positioning signal C/N at MS
- Integrity Status Flag Integrity Assurance Flag QZS-1 does not adopt this flag. Adoption of the flag after “Phase Two” is under study.
*1 QZSS definitions apply to QZS parameters only. GPS satellite parameters conform to GPS definitions. *2 LCGPS: LCGPS is the ionospheric error free linear combination of the L1P(Y) and L2P(Y) signals for GPS. *3 LCQZSS: LCQZSS is the ionospheric error free linear combination of the L1C/A and L2C signals for QZSS.
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8.1.2 Differences with GPS in terms of CNAV message on L2C and L5 signals
Table 8.1.2-1 Parameters with definitions unique to QZSS
Message type Parameter GPS definition QZSS definition*1
10
Ephemeris the offset value of Semi Major Axis
26,559,710 [m] 42,164,200 [m]
Ephemeris Eccentricity
Parameter range is restricted (max. 0.03)
No restrictions on parameter range (max. 0.5)
Integrity Status Flag Integrity Assurance Flag QZS-1 does not adopt this flag. Adoption of the flag after “Phase Two” is under study.
L2C Phasing Phase relationship between L2C and L2P(Y) QZSS would not adopt this Flag
30
TGD LCGPS*2 and L1P(Y) group delay LCQZSS
*3 and L1C/A group delay
ISCL1C/A L1P(Y)-L1C/A group delay N/A (Broadcasting value is 0.0)
ISCL2C L1P(Y)-L2C group delay L1C/A-L2C group delay
ISCL5I5 L1P(Y)-L5I5 group delay L1C/A-L5I5 group delay
ISCL5Q5 L1P(Y)-L5Q5 group delay L1C/A-L5Q5 group delay
31, 12 (47, 28)
Reduced Almanac Precondition*1
A=26,559,710+δA [m]
A=42,164,200+δA[m] (in case of 31 or 12) A=26,559,710+δA [m] (in case of 47 or 28)
e=0 e=0.075 (in case of 31 or 12) e=0 (in case of 47 or 28)
i=55 [deg] i=43 [deg] (in case of 31 or 12) i=55[deg] (in case of 47 or 28)
Ω.
=-2.6 x 10-9 [semi-circles/ second]
Ω.
=-8.7 x 10-10 [semi-circles/ second] (in case of 31 or 12) Ω.
=-2.6 x 10-9 [semi-circles/second] (in case of 47 or 28)
ω=0 [deg]
ω=270 [deg] (in case of 31 or 12) ω=0 [deg] (in case of 47 or 28)
33 (49) UTC parameter A0-n、A1-n、A2-n
UTC (USNO)-GPST relationship
UTC (NICT)-GPST relationship (in case of 33) UTC (USNO)-GPST relationship (in case of 49)
37(53)
Midi Almanac Eccentricity*1
The eccentricity value itself Max. approximately 0.03
Difference with QZS eccentricity 0.06 (in case of 37) The eccentricity value itself (in case of 53)
The difference from Midi Almanac Reference Inclination (i0)*1
The inclination value referenced by 0.3 [semi-circles].
Difference with QZS inclination 0.25 [semi-circles] (in case of 37) Difference with GPS inclination 0.3 [semi-circles] (in case of 53)
*1 QZSS definitions apply to QZS parameters only. GPS satellite parameters conform to GPS definitions. *2 LCGPS is the ionospheric error free linear combination of the L1P(Y) and L2P(Y) signals for QZSS *3 LCQZSS is the ionospheric error free linear combination of the L1C/A and L2C signals for QZSS
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8.1.3 Differences with GPS in terms of CNAV2 message on L1C signals
Table 8.1.3-1 Parameters with definitions unique to QZSS (1/2)
Sub Frame#/Page# Parameter GPS definition QZSS definition*
2/-
Ephemeris/ The offset value of Semi Major Axis
26,559,710 [m] 42,164,200 [m]
Ephemeris/ Eccentricity Maximum limit is 0.03 Full range without limitation
(i.e. Max=0.4999---)
ISCL1CP L1P(Y) – L1CP group delay L1C/A – L1CP group delay
ISCL1CD L1P(Y) – L1CD group delay L1C/A – L1CP group delay
Integrity Status Flag Integrity Status Flag QZS-1 does not adopt this flag . Adoption of the flag after “Phase Two” is under study.
3/1 (or 3/17)
UTC parameter/ A0-n、A1-n、A2-n
UTC(USNO)-GPST relationship
UTC(NICT)-GPST relationship (if Page 1) UTC(USNO)-GPST relationship (if Page 17)
ISC_L1C/A L1P(Y)-L1C/A group delay
The message for QZS-1 is not adopting this parameter on this page/subframe. Future support for this parameter is under study,
ISC_L2C L1P(Y)-L2C group delay
The message for QZS-1 is not adopting this parameter on this page/subframe. Future support for this parameter is under study,
ISC_L5I5 L1P(Y)-L5I5 group delay
The message for QZS-1 is not adopting this parameter on this page/subframe. Future support for this parameter is under study,
ISC_L5Q5 L1P(Y)-L5Q5 group delay
The message for QZS-1 is not adopting this parameter on this page/subframe. Future support for this parameter is under study,
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Table 8.1.3-1 Parameters with definitions unique to QZSS (2/2)
Sub Frame#/Page# Parameter GPS definition QZSS definition*
3/3 (or 3/19)
Reduced Almanac/ Equation to get Semi Major Axis (A) from the broadcasted δA in this page*
A=26,559,710+δA [m]
A=42,164,200+δA[m] (if the PRN number in a packet is 193-197, or page number 3) A=26,559,710+δA [m] (if the PRN number in a packet is not 193-197 and page number is 19)
Reduced Almanac/ Assumption of Eccentricity*
e=0
e=0.075 (if the PRN number in a packet is 193-197, or page number 3) e=0 (if the PRN number in a packet is not 193-197 and page number is 19)
Reduced Almanac/ Assumption of Inclination*
i=55[deg]
i=43[deg] (if the PRN number in a packet is 193-197, or page number3) i=55[deg] (if the PRN number in a packet is not 193-197 and page number is 19)
Reduced Almanac/ Assumption of changing rate of right ascension*
Ω.
=-2.6 x 10-9
[semi-circles/second]
Ω.
=-8.7 x 10-9 [semi-circle/ seconds] (if the PRN number in a packet is 193-197, or page number 3) Ω.
=-2.6 x 10-9 [semi-circles/ second] (if the PRN number in a packet is not 193-197 and page number is 19)
Reduced Almanac/ Argument of Perigee* =0 [deg]
=270 [deg] (if the PRN number in a packet is 193-197, or page number 3) =0 [deg] (if the PRN number in a packet is not 193-197 and page number is 19)
3/4 (or 3/20)
Midi Almanac/ Eccentricity*
The eccentricity value itself (Maximum range attainable with indicated bit allocation and scale factor is 0-0.03)
The eccentricity value referenced by 0.06 (if the PRN number in a packet is 193-197, or page number 4) The eccentricity value itself (if the PRN number in a packet is not 193-197 and page number is 20)
Midi Almanac/ The difference from Reference Inclination (i0)*
The inclination value referenced by 0.3 [semi-circles].
The inclination value referenced by 0.25 [semi-circles] (if the PRN number in a packet is 193-197, or page number 3) The inclination value referenced by 0.3 [semi-circles] (if the PRN number in a packet is not 193-197 and page number is 20)
* QZSS definitions apply to QZS parameters only. GPS satellite parameters conform to GPS definitions.
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8.2 Difference of RF Characteristics
8.2.1 Difference of Modulated Diffusion Method of Signal
The modulated diffusion method of LIC signal for QZS-1 is BOC (1, 1), and not same as MBOC for GPS satellite. We are studying if the modulated diffusion method of LIC signal after “Phase Two” should be MBOC.
8.2.2 Difference of Signal Phase Relation of LIC Signal
The carrier phase relation among L1 QZS-1 signals are defined that L1C/A and L1CD are same and L1CP is delayed by 90 degrees as described in Section 5.1.1.1.1. L1CD and L1CP for QZS-1 are orthogonal each other at right angles, but L1CD and L1CP for GPS are in phase (Figure 5.1.1-1).
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ANNEX
Indoor Messaging System (IMES)
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A 1 IMES Signal IMES (Indoor Messaging System)1 signal is designed to realize the indoor positioning, and has a similar property to standard satellite positioning system signal. On the other hand, the positioning method with IMES signal is totally different from standard satellite positioning method. This method is very simple and practical for specifying the position simply by demodulating and decoding the modulated navigation message. This method requires only a small customization of existing GPS receivers. In this sense, IMES has similar advantage as QZSS signal and research has been made for the promotion of QZSS. QZSS is designed to improve the availability of positioning feasible area and time in both urban and mountainous area, and IMES is designed to realize the indoor positioning which is difficult by satellite-based positioning. Both systems are intended to improve the efficiency and availability of positioning environment, that is to realize the seamless positioning in both indoor and outdoor environment. This appendix describes the signal specification of IMES-L1C/A signal which has same RF characteristics as L1C/A signal and IMES-L1C signal which has same RF characteristics as L1C signal of GPS and QZSS. Installation of IMES signals transmitter and its operation concept is also explained. IMES signal is designed by JAXA to contribute the development of QZSS-ready receivers as well as satellite positioning applications by realizing the seamless positioning environment. However, IMES signal transmitter is not part of the QZSS component, further development and installation by a third party is expected based on this specification. Please note that the PRN code set for "IMES" is ONLY authorized by US GPSW to use in JAPAN, currently. The specification of "IMES Signal" defined in this appendix is only valid in Japan. * We will set up "IMES consortium" and study finalization of the specification of IMES signal & message, and development of the guideline for installation and operation of IMES equipments in the consortium. The conclusion will be reflected in this document. The issue of time crunch for reading IMES message (discussed in QZSS user meeting (for IMES) on 22 DEC. 2010) will be studied in IMES consortium and be finalized the specification during FY2011. A 1.1 IMES signal specification
A 1.1.1 IMES signal -L1C/A type-signal specification
IMES signal -L1C/A type-(IMES-L1C/A) has the same RF characteristic as L1C/A of GPS and QZSS Navigation message structure is same in terms of 30 bits word unit, but has frame structure in terms of one word at the shortest to achieve fast TTRM (Time to Read Message). The following describes the specifications by distinguishing RF characteristics and message characteristics.
A 1.1.1.1 RF characteristics
A 1.1.1.1.1 Signal structure
A 1.1.1.1.1.1 Nominal center carrier frequency
Nominal center carrier frequency is 1575.4282 MHz or 1575.4118 MHz, and deviation is ±0.2ppm
1 Patent pending by JAXA, GNSS Technology Inc. and Lighthouse Technology and Consulting Co. (2 patents for "Positional information
providing system, Positional information providing apparatus and transmitter" (Japanese Patent No. 4296302 and 4461235) have been
approved.)
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A 1.1.1.1.1.2 PRN spreading frequency
PRN spreading frequency is one hundred fifty fourth part of nominal center carrier frequency. The carrier and PRN code should keep coherence.
A 1.1.1.1.1.3 PRN spreading modulation method
The carrier should be BPSK (1) modulated on CIMES-L1C/A bit strings by PRN code and navigation message.
A 1.1.1.1.1.4 Frequency bandwidth
2.046MHz or more including main-lobe.
A 1.1.1.1.2 Signal power level
A 1.1.1.1.2.1 Minimum signal power level at the receiver input
The minimum received power measured by the receiving antenna having gain of 0dBi for right-handed circularly polarized wave should be installed and configured in -158.5 dBW or more at the input terminal of receiver having antenna gain of 0dBi for right-handed circularly polarization.
A 1.1.1.1.2.2 Maximum signal power level at the receiver input
In cases where the power of the receiving GPS signal is estimated in -158.5dBW or more measured by the receiving antenna having gain of 0dBi for right-handed circularly polarization, the maximum received power of IMES signal should be installed and configured in -140 dBW or less at the input terminal of receiver having antenna gain of 0dBi for right-handed circularly polarization. In cases where the power of the receiving GPS signal is estimated in less than -158.5dBW measured by the receiving antenna having gain of 0dBi for right-handed circularly polarization, the maximum received power of IMES signal should be installed and configured in -150 dBW or less at the input terminal of receiver having antenna gain of 0dBi for right-handed circularly polarization.
A 1.1.1.1.2.3 Maximum signal power level at the transmitter output
Equivalent Isotropically Radiated Power (EIRP) should be installed and configured in -94.35 dBW or less at the output of IMES signal transmitter.
A 1.1.1.1.3 PRN code
Same code sequence as PRN code of C/A signal of applicable document (1), see the applicable document (1) from number 173 to 182. NOTE: Those set of PRN code are NOT allowed to use outside of Japan currently.
A 1.1.1.1.4 Navigation message
Same word structure, bit rate, and modulation scheme of applicable document (1).
A 1.1.1.1.5 Carrier wave characteristics
A 1.1.1.1.5.1 Correlation loss
Correlation loss means the difference between the transmitted power and received power by reverse diffusion. Correlation loss power level is 1.2dB or less.
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A 1.1.1.1.5.2 Carrier phase noise
Carrier phase noise of unmodulated carrier wave before PRN code and navigation message are superposed should keep the level which PLL of 10Hz one sideband of PLL is able to phase tracking at 0.2rad (RMS).
A 1.1.1.1.5.3 Spurious characteristics
Spurious power level is -40 dB or less to unmodulated carrier power level within frequency band.
A 1.1.1.1.5.4 Polarization characteristics
This means the right-hand circularly polarized spread spectrum signal or the linearly polarized spread spectrum signal. And axis ratio guarantees minimum signal power level.
A 1.1.1.2 Message Characteristics
A 1.1.1.2.1 Word structure
One word is made up of 30 bits, which is 21bits of data bits and 3 bits of word counter, 6 bits of parity.
A 1.1.1.2.1.1 Word counter
The 3 bits after second word in the frame which has multiple words is “Word counter”. This “word counter” increment every word transmission including word that word counter is not included. Identifying the segment of word and frame is assisted with word counter. This 3 bits value skips instead of taking the same value as first 3 bits of preamble for the assist of identifying the segment.
A 1.1.1.2.1.2 Parity
The 6 bit parity code added to the end of 30 bit word is the same (32.26) Hamming code as specified in 20.3.5.1 of applicable documents (1). This parity assists identifying word segment.
(1) Parity Algorithm
The 6 bit parity code added to the end of 30 bit word is the same (32.26) Hamming code as specified in 20.3.5.1 of applicable documents (1).
(2) Parity Check Algorithm
Same as the applicable document (1) in section 20.3.5.2.
A 1.1.1.2.2 Frame structure
One frame is made (consists) of multiple number of integer of one word and has following style indicated on the figures shown in Figure 1.1.1-1. This figure indicates the example by 3 words/frame. In case of over 4 words/frame, 3 bits word counter is repeated after second word as necessary times. That is to say, first word comes with 8 bit preamble and 3 bits message type ID (MID) follows. The others bits are all data bit except above 3 bits word counter and 6 bits parity.
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Bits -> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
COUNT Data BitsCOUNT Data Bits
COUNT Data Bits
ParityParity
Parity
Data Bits
Data Bits
in case of3 words/frame
in case of2 words/frame
ParityPreamble
Parity
Message Type
ID
Message Type
IDData Bits
in case of1 word/frame
Preamble
Preamble ParityMessage Type
ID
Figure 1.1.1-1 IMES L1C/A frame structure
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A 1.1.1.2.2.1 Preamble
The 8 bits preamble added to the beginning of the first word of each frame is 8B(H) Identifying the each word and frame segment is assisted with this preamble. This value allows the identification of IMES signal from GPS and QZSS, unlike the applicable document (1) in section 20.3.3.1.
A 1.1.1.2.2.2 Message type ID (MID)
3 bits message type ID (MID) which is added to the preamble of the first word of each frame indicates its frame length and contents. Table 1.1.1-1 shows the MID value and its associated frame length, contents, and Maximum Repetition Cycle (s). The Maximum repetition Cycle is defined that absolute position information is sent from the IMES transmitter at each cycle. Because of this, users could get not only ID type message but also absolute position information without data server for disaster-management in emergency situations.
Table 1.1.1-1 Definition of IMES L1C/A message type ID
MID
Frame
Length
(words)
Contents Maximum Repetition
Cycle (s) (provisional)
0 3 Position 1 12
1 4 Position 2
2 - reserved -
3 1 Short ID -
4 2 Medium ID -
5 - Reserved -
6 - Reserved -
7 - Reserved -
A 1.1.1.2.3 Message contents
A 1.1.1.2.3.1 Message type ID ”000” position data 1
When the Message type ID is ”000”, the frame length is 3 words and its contents indicates the position data. This position data will be consistent with the position data code using Ucode defined and managed by Geographical Survey Institute. Frame structure is indicated on the Figure 1.1.1-2, refers to the Table 1.1.1-2 for the LSB and numerical range.
(1) Floor number
The first word bit 12 to 19 indicated the floor number where the transmitter is placed, and FL(th) is the unit. Bits are unsigned 8 bit and LSB is a floor. As it is indicated in the equation below, -50FL to +204FL is the range of these bits by setting the offset at -50 FL.
][502 FLrFloorNumbe rBitsFloorNumbe
(2) Latitude
The second word bit 4 as signed bit, bit 5 to 24 as MSB, and the bits 20 and 21 in the first word as LSB, are the latitude of transmitter and degree is the unit.
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These total 23 bits are singed, LSB is [deg]000021.0[deg]2/90 22 , and the range is from 0deg to +90deg (from -90deg to +90deg with signed bit). It is equivalent to nearly 2.4m in the north and south direction.
(3) Longitude
The third word bit 4 as signed bit, bit 5 to 24 as MSB, and the bits 22-24 in the first word as LSB, are the longitude of transmitter and degree is the unit. These total 24 bits are signed, LSB is [deg]000021.0[deg]2/180 23 , and the range is from 0deg to +180deg (from -180deg to +180deg with signed bit). It is equivalent to nearly 2.4m in the east and west direction on the equator.
Bits -> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
word 1
0 0 0
word 2
word 3
Lon
LSB
3bi
ts Parity6bits
Preamble, 8bit
MSGType,3bit L
atLSB
Floor 8bit
Parity6bits
ParityCNT3bit
CNT3bit
Latitude 21bits (MSB)
Longitude 21bits (MSB)
Figure 1.1.1-2 IMES-L1C/A MID=000 « Position 1 » Frame Structure
Table 1.1.1-2 IMES-L1C/A MID=000 « Position 1 » Contents
~1 ~2 ~3 ~24
8
Bit LengthContent
23
#
FloorLatitude
Longitude (2.39 m)(2.39 m)
1 th
LSB
2.1E-05 deg2.1E-05 deg
-50 th
-180 deg-90 deg
Rangemaximumminimum204 th90 deg180 deg
A 1.1.1.2.3.2 Message type ID ”001” position data 2
When the Message type ID is ”001”, this frame length is 4 words and its content indicates the position data. Frame structure is indicated on the Figure 1.1.1-3, and refers to the Table 1.1.1-3 for the LSB and range.
(1) Floor number
The first word bit 12 to 20 indicated the floor number where the transmitter is placed, and FL(th) is the unit. Bits are unsigned 9 bits and LSB is 0.5 floor. As it is indicated in the equation below, -50FL to +205FL is the range of these bits by setting the offset at -50 FL.
][5025.0 FLrFloorNumbe rBitsFloorNumbe
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(2) Latitude
The second word bit 4 as signed bit, bit 5 to 24 as MSB, and the bits 18-20 in the fourth word as LSB, are the latitude of transmitter and degree is the unit. These total 24 bits are signed, LSB is [deg]000011.0[deg]2/90 23 , and the range is from 0deg to +90deg (from -90deg to +90deg with signed bit). It is equivalent to nearly 1.2m in the north and south direction.
(3) Longitude
The third word bit 4 as signed bit, bit 5 to 24 as MSB, and the bits 21-24 in the fourth word as LSB, are the longitude of transmitter and degree is the unit. These total 25 bits are signed, LSB is [deg]000011.0[deg]2/180 24 , and the range is from 0deg to +180deg (from -180deg to +180deg with signed bit). It is equivalent to nearly 2.4m in the east and west direction on the equator.
(4) Altitude
Fourth word bit 4 to 15 are the altitude of transmitter, and m (meter) is the unit. These total 12 bits are unsigned, and as it is indicated in the equation below, it indicates the value in the range from -95m to +4000m by setting the offset at -95m.
][952 mAltitude tsAltitudeBi
Bits -> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
word 1
0 0 1
word 2
word 3
word 4 CNT3bit
Altitude 12 bits Lat
(LSB
)
reserved
rese
rved
Lon
(LSB
)
Floor 9 bits
Parity6bits
Parity
CNT3bit
Latitude 21bits (MSB)
CNT3bit
Longitude 21bits (MSB)
Parity6bits
Preamble, 8bit
MSGType,3bit
Parity
Figure 1.1.1-3 IMES-L1C/A MID=001 « Position 2 » Frame Structure
Table 1.1.1-3 IMES-L1C/A MID=001 « Position 2 » Contents
~1 ~2 ~3 ~4 ~ 4000 m
90 deg180 deg
205 th
Range#
maximum
2512
Bit LengthContent
24
Altitude
LatitudeLongitude (1.19 m)
(1.19 m)
1 m
LSB
1.1E-05 deg1.1E-05 deg
-95 m-180 deg-90 deg
minimumFloor 9 0.5 th -50 th
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A 1.1.1.2.3.3 Message type ID ”011” short ID
In the event that Message type ID is ”011”, this frame length is 1 word and its contents is short ID(IDS). Figure 1.1.1-4 shows the frame structure and IDS of 12 bit is transmitted. IDS=111111100000~111111111111 is the bit pattern reserved for some specific purposes, for instance, emergency message when disaster occurs, should not be used in general.
Bits -> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
word 1
0 1 1
Parity6bits
Preamble, 8bit
MSGType,3bit
Short ID (IDS)
12 bits
BD
1bi
t
Figure 1.1.1-4 IMES-L1C/A MID=011 « Short ID » Frame Structure
A 1.1.1.2.3.4 Message type ID ”100” Medium ID
In the event that Message type ID is ”100”, this frame length is 2 words and its contents is medium ID(IDM). Figure 1.1.1-5 shows the frame structure and IDM (length=33 bits) is transmitted.
Bits -> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
word 1
1 0 0
word 2 CNT3bits
Medium ID (IDM)
LSB 21 bitsParity6bits
Parity6bits
Preamble, 8bit
MSGType,3bit
Medium ID (IDM)
MSB 12 bits
BD
1bi
t
Figure 1.1.1-5 IMES-L1C/A MID=100 « Medium ID » Frame Structure
A 1.1.2 IMES-L1C type-signal specification
TBD
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A 1.2 Installation of transmitter
This chapter is scheduled to explain the transmitter installation such as the example of separation distance between transmitter and receiver as below, as well as the interval between transmitters, and how to choose the PRN number for each transmitter, etc.
A 1.2.1 Examples of separation distance from transmitter to receiver
Examples of separation distance and transmitter EIRP in accordance with maximum receiving power limit of IMES signal L1C/A type is shown in Figure 1.2.1-1.
Figure 1.2.1-1 Examples of separation distance and transmitter EIRP in accordance with maximum receiving
power limit of IMES signal
A 1.3 Operation concept
This chapter is schedule to describe the application examples of IMES for indoor positioning.