Radio Technical

Commission for Maritime

Services

RTCM SC-104: Enabling Standards

that Support Emerging Positioning

and Related Technologies

Rudy Kalafus, Previous Chair and

Kendall Ferguson, Current Chair, SC-104

PPP-RTK and Open Standards Symposium

Frankfurt am Mein, Germany

12 March 2012

Open Standards: RTCM & RTCA

RTCM SC-104: Differential GNSS

Conventional DGNSS

Single-Station RTK

Networked RTK

Multiple GNSS operation

RTCM Contact Info�

Topics:�

RTCM = Radio Technical Commission for

Maritime Services

RTCM founded in 1947 as

U.S. State Department Advisory Committee

Now an independent membership

organization�

What is RTCM?�

RTCM supports development of standards

and regulations of:

• International Maritime Organization (IMO)

• International Telecommunications Union (ITU)

• International Electrotechnical Commission (IEC)

• International Organization for Standardization (ISO)

RTCM Standards Work

European Telecommunications Standards Institute

(ETSI)

Comité International Radio-Maritime (CIRM)

Cospas-Sarsat

International Association of Aids to Navigation and

Lighthouse Authorities (IALA)

International Hydrographic Bureau (IHB)

National Marine Electronics Association (NMEA)

RTCM Liaisons

RTCM Members

22 Government Agencies from 5 nations

61 Manufacturers from 13 nations

45 Others:

Associations Service Providers

Designers Vessel Owners/Operators

Trainers

SC104: Differential Global Navigation

Satellite Systems (DGNSS)

SC109: Electronic Charting Technology

SC123: Digital Messaging over Maritime

Frequencies

RTCM Standards

Used Internationally

SC101: Digital Selective Calling marine radios

SC110: Emergency Beacons

SC112: Radar

SC117: Electromagnetic Interference Resistance for

marine radios

SC119: Maritime Survivor Locating Devices

RTCM Regional Standards

Used in USA

SC-104 Differential GNSS

Standards - Types

• Standards include:– Differential GNSS Data Link Messages, for

conventional differential and RTK services

– Reference Station Integrity Monitor system design standards (RSIM)

– Standards for intra-network messages: Networked Transport of Rtcm via Internet Protocol (NTRIP)

– Receiver-INdependent Exchange (RINEX) standards, jointly with the IGS (recent)

SC-104 Working Groups

• Current Working Groups and Chairs:– Network RTK Hans-Jürgen Euler

– Internet Protocol Georg Weber

– GLONASS Alexei Zinoviev

– Galileo Hans-Jürgen Euler

– DGNSS Beacon Services Allen Cleveland

– Private Services Ivo Milev

– State Space *** Gerhard Wübbena

– Version 3 Paul Alves

– Multiple Signal Operation Gleb Zyryanov

– Coordinate Transformations Martin Schmitz

– RINEX Ken MacLeod

*** Gerhard Wübbena and Martin Schmitz will present papers on State Space message development

SC-104 Differential GNSS

Standards - Versions 1 & 2

• Originally set up in 1983 to develop standards for DGPS to achieve 5 meter accuracy navigation & positioning

• Version 1 was replaced by Version 2, when implementation problems turned up (1990)

• Version 2.1 added Real-Time Kinematic(RTK) messages to provide decimeter accuracy over short ranges (1994)

• Version 2.2 expanded differential operation to GLONASS, provided ancillary RTK messages (1998)

• Version 2.3 added several new messages to improve RTK, radiobeacon broadcasts, use of Loran-C (2001)

• Version 2.4 under development; will support Differential Galileo and new frequencies

SC-104 Differential GNSS

Standards - Version 3

• Version 2 was a good solution for conventional DGNSS services with low bandwidth broadcasts

• Version 3 was designed with RTK services and higher bandwidth data links in mind - more efficient, higher integrity, more capability and room for expansion

• Version 3.0 (2004) was intended at improve RTK services for GPS & GLONASS at L1 & L2

• Version 3.1 (2006) added messages to support networked RTK, proprietary messages, and auxiliary data

SC-104 Differential GNSS

Standards - Version 3

• Amendments have been added to Version 3.1:– 1: Added Coordinate Transformation Messages

– 2: Added RTK Residual Error Messages

– 3: Added section on handling quarter-cycle carrier phase shifts

– 4: Added State Space Messages

– 5: Added sections on GLONASS MAC and FKP, two network embodiments

• Proposed Amendment 6 would add Multiple Signal Messages that accommodate multi-system, multi-frequency operation

SC-104: Developing Open

Standards

• SC-104 standards are developed in an open forum

• Participating companies and governments benefit from world-wide standards

• Participants include vendors, service providers, and government agencies from around the world

• The open forum and the nature of the market encourage companies to develop open standards

• Standards are subjected to performance and inter-operability testing prior to adoption and publication

• Although RTCM was originally set up to address maritime standards, DGNSS standards are applied world-wide to land and maritime positioning systems

SC-104: Criteria for Good

Message Standards

• Clarity: data terms and instructions should be unambiguous

• Completeness: data terms should form a complete set

• Targeted minimum system accuracy and update rate: should be spelled out

• Data term range and resolution: must support accuracy

• Temporal: data must retain accuracy for long enough to achieve stated minimum system accuracy

• Testing: prior to publication, the above criteria should be demonstrated and tested by more than one vendor

• Interoperability: messages should be tested using equipment from different vendors

SC-104: Evolution of DGNSS

Standards

• Early standards developed to support conventional differential GPS, with single reference station

• GLONASS and RTK services were then added

• With higher bandwidth data links available and higher precision needed, a better format was developed

• As networks came into use, the NTRIP standard was developed and new messages were formed

• For consistency of broadcast data, wide-area ground station equipment required standards, leading to RSIM

• With Galileo, QZSS and other satellite systems being developed, service providers want to use all signals

• Recent work has emphasized multi-system, multi-signal, high-precision operation

SC-104: Evolution of DGNSS

Standards

• To date, DGNSS standards have been published for operational systems, namely GPS and GLONASS, validated by interoperability testing

• DGNSS Standards are in preparation for the European Galileo GNSS and the Japanese QZSS, and will be published once validation tests have been performed

• The SC-104 standards can accommodate the Chinese COMPASS system as its development proceeds and documentation and test equipment becomes available

SC-104: Multiple Signal

Message Development

• With several GNSSs operational or coming on line, and with new frequencies, service providers want to use as many signals as possible

• SC-104 is undertaking a major development effort to meet this need; formed MSM Working Group with Gleb Zyryanov of Ashtech as chair

• The more generic format takes advantage of the availability of higher bandwidths

SC-104: Multiple Signal

Message Features

• Universality for existing and future GNSS signals

• Flexibility and Scalability

• Compactness: takes advantage of common properties of different signals to compress data and reduce bit count

• Simplicity of data formulation and reduction

• Highly compatible with RINEX-3

• Replaces a number of current system-specific messages

SC-104 Summary

• RTCM SC-104 remains highly active in the development of standards to support high-precision, real-time positioning

• SC-104 is working closely with the International GNSS Service (IGS) to harmonize the RINEX and RTCM standards, in order to simplify vendor and service provider workloads

• SC-104 continues to support regional conventional DGNSS service world wide

Radio Technical Commission

for Maritime Services

President: Robert Markle

www.rtcm.org