cdot cors/opus team p. fromhertz colorado state geodetic advisor national geodetic survey (ngs)...

CDOT CORS/OPUS Team

P. Fromhertz

Colorado State Geodetic AdvisorNational Geodetic Survey (NGS)

January 13, 2011

Gotomeeting

https://www2.gotomeeting.com/join/544417138

Call in number: 877-988-6989 participant passcode: 1680881

Topics

• CDOT CORS/OPUS Team formed

• Review Goals/Purpose of Team

• What is CORS and OPUS

• Review Articles

• Examine Pilot data

• Set Next Steps

• Determine if CORS/OPUS can fulfill

CDOT needs

• Update Manual

• Understand whether CDOT needs more CORS

across the State and if so where and at what

density.

Topics

1. Use CORS/OPUS to bring in horizontal control to a project area to serve as a starting position instead of

tieing into a HARN.

2. Use CORS/OPUS to get coordinates on all your survey control project horizontal coordinates (instead of running RTK).

3. Use CORS/OPUS to establish a vertical starting height for a project area.

4. Use CORS/OPUS on project control vertically.

2003 2004 2005 2006 2007 2008

OPUS-RS 0 0 0 0 19 43

OPUS-S 33 59 76 100 121 109

UFCORS 92 92 114 158 190 209

CORS FTP 128 165 101 146 158 282

TOTAL 253 316 291 404 488 643

CORS Annual Benefits

2010 May 11 Federal Geospatial Summit 8

time zone

start time

# hours

select CORS

epoch rate

coords, met, datasheet, orbits, zip?

RINEX: 1 hour @ 30-second epoch = 125KB

User Friendly CORS

Why do we need OPUS?• Recognize most positioning done with GPS• Want to provide fast, accurate, consistent,

reliable access to NSRS• CORS data alone does not ensure consistency• OPUS

– NGS computers– NGS software– Standard parameterization– Standard coordinates/velocities– Your machine talks to our machine

What is OPUS?• OPUS is an acronym for:

– Online Positioning User Service (OPUS)

• It started as a service for Static GPS users and has grown from there to serve other users.

• Designed to work with minimal data input from user and be as fully automated as possible.

• Only a Web Browser and Email needed to use.• Fast, easy, consistent access to NSRS.

Many Flavors of OPUS Planned

• OPUS-S (static)» $$$ receiver, hours of data

• OPUS-RS (rapid static)» $$$ receiver, minutes of data

• OPUS-DB (database)» $$$ receiver, hours of data, share results

• OPUS-Projects – Beta» Multiple $$$ receivers, share results

• OPUS-GIS – not released ??» ¢¢ receiver, minutes of data

• OPUS-Leveling – LOCUS

OPUS has been popular

• L1/L2 GPS data >>> www.ngs.noaa.gov/OPUS

• Processed automatically on NGS computers

• OPUS-S (2-48 hrs): ties to 3 CORS or

• OPUS-RS (15 min–2 hrs): ties to 9 CORS

• Solution via email - in minutes

• Fast, easy, consistent access to NSRS

Online Positioning User Service (OPUS)

How does OPUS work?

• Each OPUS ‘flavor’ is a bit different

• Let’s start with OPUS-S

• Then, we’ll highlight the differences in – OPUS-RS – OPUS-DB– OPUS-Projects

OPUS-S

• OPUS-Static, (formerly just called OPUS and sometimes now called OPUS-CLASSIC)

• Basic Steps– Submit GPS data to OPUS Web site– Processed automatically on NGS computers

• Ties to 3 CORS stations

– Solution via email - in minutes– Fast, easy, consistent access to NSRS

How Does OPUS Compute Position?

• NGS-PAGES software used• L3-fixed solution w/ tropo adjusted• 3 “best” CORS selected• 3 separate baselines computed• 3 separate positions averaged• Position differences also include

any errors in CORS coordinates

How Does OPUS select CORS1. Estimate remote station position

2. Compute distance to every available CORS

3. Selected CORS assigned 0.0 distance

4. Sort CORS by increasing distance

5. Select the 5 closest CORS

6. Look at 1st 3 CORS with TEQC program

● covers remote data span

● > 80% data available

● low multipath

● replace with 4th (then 5th)

7. Start single baseline solutions on 1st 3 CORS

● check solution quality

● if bad solution, replace CORS with 4th (then 5th)

OPUS Guidelines

• Email address for results• Data file with 2 hrs to 48 hrs of GPS L1/L2

data – Static GPS observations only– 30-second epochs processed– not approved for less than 2 hrs of data, but you

can try

• Antenna type/phase model • Antenna height from mark-to-ARP vertical

OPUS Website (all flavors)http://www.ngs.noaa.gov/OPUS/

OPUS Inputs

• Email – pamela.fromhertz@noaa.gov• GPS file - .dat or Rinex (.obs)

– you may zip several files together – IF they all have same antenna type and antenna height. – Antennas need not be same serial numbers

Allowable Data Formats

• RINEX Receiver Independent Exchange—uncompressed

• Manufacturer’s native / raw (binary)—Uncompressed--as long as UNAVCO’s TEQC program can process it

• Compressed archive of multiple files. Archive must contain RINEX “site123h.04o” or Hatanaka “site123h.04d”

• Compressed individual files.“Site123h.zip”must contain “site123h.06o” or “site123h.06d”

OPUS Inputs

• Antenna Type – TRM41249.00 (choose from list)• Antenna Ht – vertical measure from mark to ARP

Antenna Height• True vertical distance• measured in meters

Why Do I Need the Antenna Type?

L1/L2 phase centers are around here

Antenna Reference Point (ARP)

antenna offsets relate ARP w/ phase centers & are passed to processing software

if no antenna type selected, offsets are set to 0 & phase center becomes the referenceincorrect or missing antenna type

large vertical errors

Antenna Phase Center

Variation............

SV 14SV 2

Antenna

Type A

Antenna

Type B

Different

Phase Patterns

SV elevation and varying phase patterns affect signal interpretation differently

OPUS Inputs

• Antenna Type – TRM41249.00 (choose from list)• Antenna Ht – vertical measure from mark to ARP• Options – Next 3 slides

OPUS Inputs (OPTIONS 1 & 2)

specifySPCS

specifyCORS

OPUS Inputs (OPTIONS 3, 4, & 5)

Specify GEOID model:AutoGEOID09GEOID03

Choose OUTPUT type

Choose XML or not

OPUS Inputs (OPTIONS 6, 7, & 8)

OPUS-Projects Keyword

Set USER Profile

Choose PUBLISH and Submit

OPUS Positions

• NGS PAGES processing software

• Ionospheric-free solution

• Tropospheric scale height adjusted

• Fixed ambiguities

• Average of 3 unique CORS ties

• ITRF & NAD83

coordinates/errors

CORS A

CORS B

CORS C

Average

OPUS Report

OPUS Report – check results• > 90% observations used• > 50% ambiguities fixed• < 3 cm overall RMS

• < 5 cm peak-to-peak errors

• check antenna info

• check ephemeris type

…and which CORS were used? … resubmit later for better CORS scenario & ephemeris

How Does OPUS Compute Errors?

1 σ standard deviation

peak-to-peak error more conservative ~ 2 σ

peak-to-peak distances

WHAT IS A GOOD SOLUTION?

• No hard rules - only guidelines• Make sure antenna type and antenna height are correct• Review statistics• should use 90% or more of your observations• at least 50% of the ambiguities should be fixed• overall RMS should seldom exceed 3.0 cm• peak to peak should seldom exceed 5.0 cm

• Precise (Final)• 14 days latency• 1 cm accuracy• updated weekly

• Rapid• 1 day latency• 2 cm accuracy• updated daily

• UltraRapid• 24 hrs observed / 24 hrs predicted• 5 cm / 10 cm accuracy• updated 4 times/day

NGS/IGS PRECISE ORBITS

OPUS Extended Output• HTDP-transform CORS ITRF coordinates from

published epoch to session midpoint

• Remote station ITRF solution from each CORS

• G-files – vector components, standard deviations, & correlations for each vector

• post-fit RMS & # observations per satellite/vector

• solution covariance matrix-relates errors in each coordinate to every other coordinate

• network accuracies - H & V

• summary of NAD83 derivation

• SPC feet values, if available for user’s state

Articles

• Accuracy of OPUS solutions for 1- to 4-h

observing sessions, NGS et. al., 2005

• Geodetic Connections – OPUS Rapid State, D. Martin, The American Surveyor, 2007

• Accuracy assessment of the National Geodetic Survey’s OPUS-RS utility, NGS et al., 2009

• Rover Station Positional Accuracies from OPUS as a Function of Reference Station Spacing and Rover Station Occupation Time, NGS et al,. 2009

R5 Pilot Data

R5 Pilot Data• Static Data

– S 422– U 422– X 423

• RTK data, CDOT control– MP192.10– MP192.28– MP192.45– MP192.55– MP192.62

How much does it matter if you use the correct antenna?

Station X 423 Lat W Long Ellipsoidal HTNGS DataSheet 39.40503 46.58116 2327.094TRM14532.00 39.40504 46.57941 2327.075TRM_R8_GNSS 39.40523 46.57984 2327.106

Differences DataSheet - TRM14532 -1E-05 0.00175 0.019DatasSheet - TRM_R8_GNSS -0.0002 0.00132 -0.012

OBS Used # Fixed AMB Overall RMSTRM14532.00 98% 89% 0.15TRM_R8_GNSS 98% 98% 0.13

Units all in meters

How much does it matter if you use the correct antenna?

Station X 423 Lat W Long Ellipsoidal HTNGS DataSheet 39.40503 46.58116 2327.094TRM14532.00 39.40504 46.57941 2327.075TRM_R8_GNSS 39.40523 46.57984 2327.106TRM_R8_GNSS Day 101 39.40577 46.58123 2327.106

Differences DataSheet - TRM14532 -1E-05 0.00175 0.019DatasSheet - TRM_R8_GNSS -0.0002 0.00132 -0.012DataSheet - TRM_R8_GNSS Day 101 -0.00074 -7E-05 -0.012

OBS Used # Fixed AMB Overall RMSTRM14532.00 98% 89% 0.15TRM_R8_GNSS 98% 98% 0.13Day 101 98% 95% 0.12

Units all in meters

How much does it matter if you use the correct antenna?or which CORS?

Station X 423 Lat W Long Ellipsoidal HTNGS DataSheet 39.40503 46.58116 2327.094TRM14532.00 39.40504 46.57941 2327.075TRM_R8_GNSS 39.40523 46.57984 2327.106TRM_R8_GNSS Day 101 39.40577 46.58123 2327.106TRM_R8_GNSS 3 Different CORS 39.40518 46.58099 2327.116P037, AZCN, CNC1 P037, MC02, P028 39.40516 46.58114 2327.108POB5, MYT2, ZAB2 39.405 46.58022 2327.115

Differences DataSheet - TRM14532 -1E-05 0.00175 0.019DatasSheet - TRM_R8_GNSS -0.0002 0.00132 -0.012DatasSheet - TRM_R8_GNSS Day 101 -0.00074 -7E-05 -0.012TRM_R8_GNSS 3 Different CORS -0.00015 0.00017 -0.022P037, MC02, P028 -0.00013 2E-05 -0.014POB5, MYT2, ZAB2 3E-05 0.00094 -0.021

OBS Used # Fixed AMB Overall RMSTRM14532.00 98% 89% 0.15TRM_R8_GNSS 98% 98% 0.13Day 101 98% 95% 0.12TRM_R8_GNSS 3 Different CORS 98% 92% 0.16P037, MC02, P028 98% 93% 0.16POB5, MYT2, ZAB2 98% 94% 0.17

Units all in meters

OPUS-RS (Rapid Static)

• 15-minute sessions minimum, 4 hr maximum• ties to 3 – 9 CORS (< 250km)• uses RSGPS vs. PAGES software• P1/P2 code & L1/L2 phase observations• resolves all ambiguities with LAMBDA• similar to Real-Time Network computations• RSGPS solution modes:

– network: solves ambiguities, tropo, iono– rover: tropo and ion interpolated to rover

• ~10,000 lines of code

OPUS-RS geographical coverage (15 minute session)

Don’t use

OPUS-RS

outside areas

Insufficient

CORS exist.

OPUS-RS geographical coverage (60 minute session)

Don’t use

OPUS-RS

outside areas

Insufficient

CORS exist.

OPUS-RS Output

“#Fixed Ambiguities” replaced by “Quality Indicator”• average of W-ratio (separation between candidate sets of

ambiguities) of last 3 epochs• reported as network mode / rover mode• look for values > 3 for confidence in solution

NGS OPUS-RS SOLUTION REPORT USER: william.stone@noaa.gov DATE: October 29, 2007 RINEX FILE: 1207287x.07o TIME: 14:39:04 UTC

SOFTWARE: rsgps 1.09 RS11.prl 1.12 START: 2007/10/14 23:27:15 EPHEMERIS: igr14490.eph [rapid] STOP: 2007/10/15 00:00:15 NAV FILE: brdc2870.07n OBS USED: 1962 / 2082 : 94% ANT NAME: ASH701975.01A QUALITY IND. 34.21/ 37.91ARP HEIGHT: 0.0 NORMALIZED RMS: 0.307

REF FRAME: NAD_83(CORS96)(EPOCH:2002.0000) ITRF00 (EPOCH:2007.78627) LAT: 36 2 52.79767 0.008(m) 36 2 52.81498 0.008(m) E LON: 252 2 18.45532 0.013(m) 252 2 18.41156 0.013(m) W LON: 107 57 41.54468 0.013(m) 107 57 41.58844 0.013(m) EL HGT: 1974.304(m) 0.005(m) 1973.396(m) 0.005(m) ORTHO HGT: 1995.280(m) 0.026(m) [Geoid03 NAVD88]

OPUS-RS Output

“Overall RMS” replaced by “Normalized RMS”• unitless quantity, “expected” = 1• aka standard deviation of unit weight• if > 1, noisy data somewhere• typically <1, meaning noise less than expected

OPUS-RS Output

Peak-to-Peak replaced by Est. Standard Deviations• approximately 95% confidence• derived from scatter of single baseline solutions • formal standard deviations (optimistic) available in

Extended Output

OPUS-RS Station Selection

OPUS-RS Interpolative Dilution of Precision (IDOP)

OPUS-RS accuracy is dictated by CORS geometry and distances

IDOP = local CORS geometry relative to rover location[min = 1/sqrt(#CORS)]

RMSD – CORS distances

* Forthcoming paper in “GPS Solutions” –Accuracy Assessment of the NGS’s OPUS-RS UtilityBy C. Schwarz, R. Snay, & T. Soler

Expected OPUS-RS Standard Error Values in E or N Dimension:

OPUS-RS Usage

Estimated Vertical Standard Errors – f(IDOP & RMSD)15-Minute OPUS-RS Sessions

Estimated Horizontal Standard Errors – divide by 3.6

OPUS - RS

FILE: x4232091_60.10o 000191272 6015 OPUS-RS will not attempt a solution because the submitted data was collected at a location that is more than 50 km outside of the area spanned by the set of CORS sites whose GPS data OPUS-RS would use in processing the submitted data.

These CORS sites are: r301 mc10 se01 mc05 gsc1 mc08 p031 mc07 mc02

Your station is 59.5 KM outside the polygon enclosing the reference stations

Keys to Processing OPUS data

• Record Model Number and serial numbers of antenna

• Use Fixed HT tripods• Use original file where you can (*.dat file)• Check solution

OPUS-DataBase (DB) Datasheet

OPUS-DB Uses:

• GPS on BMs

• PLSS / GCDB

• Data archive

• Data sharing

Next Steps

• Schedule Monthly Meetings• Continue looking at and comparing data• Target date to Update manuals

Thank You!

Pamela.fromhertz@noaa.gov

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