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Real-Time and Near Real-Time GPS Products and Services from Canada. Y. Mireault, P. Tétreault, F. Lahaye, P. Collins, M. Caissy Geodetic Survey Division, Natural Resources Canada (GSD/NRCan) http://www.geod.nrcan.gc.ca IGS Analysis Center Workshop 2008 June 2-6, 2008

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Real time and near real time gps products and services from canada l.jpg
Real-Time and Near Real-TimeGPS Products and Services from Canada

Y. Mireault, P. Tétreault, F. Lahaye, P. Collins, M. Caissy

Geodetic Survey Division, Natural Resources Canada (GSD/NRCan)

http://www.geod.nrcan.gc.ca

IGS Analysis Center Workshop 2008

June 2-6, 2008

Miami Beach, Florida, USA


Outline l.jpg
Outline

  • NRCan Ultra Rapid Products (EMU)

  • CSRS Precise Point Positioning Service (CSRS-PPP)

  • Canadian RT GPS Tracking Network

  • Canadian High Precision RT GPS Wide-Area Correction Service (GPS·C)

  • Final Notes


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1. NRCan Ultra Rapid Products (EMU)

1.1 Description

  • Orbits and clocks for RT/NRT usage

  • Covers 48h, i.e. 24h estimated and 24h predicted

  • Produced every hour

  • ~1h delay for orbits and ~1.5h delay for clocks

  • Submission to IGS every 6h

  • Predicted orbits used inGPS·C

  • Estimated orbits and 30-sec satellite clocks used in NRT PPP



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1.3 Precision*

  • (*) Orbit and Clock Median RMS when compared to IGS Rapid (IGR)

  • (a) Orbits and clocks are used in NRT PPP

  • (b) Orbits are used in GPS·C


2 csrs precise point positioning ppp l.jpg

A Web based global positioning service for single GNSS datasets (currently GPS only; GLONASS planned)

Initiated in the Fall of 2003 as next-day service (17h delay)

Delay reduced to 90min (May 2008) using NRCan Ultra Rapid orbits and 30sec clocks

Process static or kinematic (both with single or dual frequency data)

Use of IGS IONEX grids for single frequency processing

2. CSRS Precise Point Positioning (PPP)

2.1 Description


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2.2 CSRS-PPP Usage datasets (currently GPS only; GLONASS planned)


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1.4 datasets (currently GPS only; GLONASS planned)

EMU (30sec)

1.2

IGR (5min)

1

IGS 5min

IGS 30sec

0.8

Mean Differences (cm)

0.6

0.4

0.2

0

-0.2

Ellipsoidal height

Latitude

Longitude

-0.4

2.3 CSRS-PPP Static Positioning Corrections(wrt IGS05)

Statistics based on processing of 30 secs data from 24 hour files for ALGO DRAO RESO SASK STJO for GPS Week 1470


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EMU (30sec) datasets (currently GPS only; GLONASS planned)

25

IGR (5min)

IGS 5min

20

IGS 30sec

15

Mean position variations (cm)

10

5

0

Latitude

Longitude

Ellipsoidal height

2.4 CSRS-PPP Kinematic Positioning Variations (wrt IGS05)

Statistics based on processing of 30 secs data from 24 hour files for ALGO DRAO RESO SASK STJO for GPS Week 1470


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3. datasets (currently GPS only; GLONASS planned)Canadian RT GPS Tracking Network


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Pseudorange & Phase Processing from IGS-RT + RT-CACS Stations

P3 = r(Xsta,Xsat) + c · ( dtsta – dtsat ) + dtrop + e

L3 = r(Xsta,Xsat) + c · ( dtsta – dtsat ) + dtrop + lN + e

Xsat provided by EMU (1h cycle) || IGU (6hr cycle) predictions

dtsta, dtsat,dtrop,N estimated in real-time

Enhancement of the current code-based system

4.GPS·C: Canadian High Precision RT GPS Wide-Area Correction Service

4.1 Description (1/2)


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  • Modeled Effects Stations

    • Earth & ocean tides

    • Station & satellite absolute PCV

    • Relativity

    • ITRF station velocity

    • Phase wind-up

  • Parameters Estimated

    • Station and satellite clocks (white noise parameters wrt VRC)

    • Station troposphere ZPD (random-walk)

    • Constant (float) ambiguities

  • RT High Precision Correction Stream

    • Xsat-BRD @ 120sec (linear over 240sec)

    • dtsat-BRD @ 2sec

4.1 Description (2/2)



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4.3 GPS·C Development Stations

  • Status

    • Access to 50+ real-time stations globally

    • Finalizing stress-tests & application robustness improvements

    • IOC targeted for Fall 2008  Pilot Project / ESS activities

  • Further Refinements to the Phase-based Algorithm & Models

    • YAW model (Kouba, GPS Solutions (online))

    • Un-differenced integer ambiguity resolution with decoupled clocks

    • Define BRD-independent orbit messages

    • Define messages for troposphere-mapping grid, satellite DCB’s

    • Define messages required for PPP ambiguity resolution


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4.4 StationsDay-Boundary Clock Jumps / Decoupled Clocks


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5. Final Notes Stations

  • IGS Ultra Rapid Combination

    • Push it to a 3h cycle? Ultimate goal of 1h cycle?

    • Reduce delay from 3h to 2h?

    • Need more AC clock solutions to improve precision and accuracy!

  • Global RT GPS Tracking Network

    • Would provide faster data for Ultra Rapid orbits/clocks turnaround

  • Need for 30sec satellite clocks for Rapid and

    Ultra Rapid products (NRT users such as PPP)


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  • Information on decoupled clocks Stations

    • “Isolating and Estimating Undifferenced GPS Integer Ambiguities”,

      Paul Collins, GSD, NRCan

      • Presented at the Institute of Navigation, NTM 2008, San Diego,

        January 28-30 2008, session D3.

      • Look also for the corresponding paper in the ION TNM proceeding.



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Statistics based on processing of 5 min data from files

24 hour files for ALGO for GPS Week 1470


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6 files

EMU (30sec) Latitude

5

EMU (30sec) Longitude

4

EMU (30sec) Ellip. Height

3

IGS 30sec Latitude

IGS 30sec Longitude

2

IGS 30sec Ellip. Height

1

Mean corrections (cm)

0

0

2

4

6

8

10

12

14

16

18

20

22

24

-1

-2

-3

-4

-5

2.5 CSRS-PPP Static Positioning Corrections

(wrt IGS05)

Hours

Statistics based on processing of 30 secs data from 24 hour files for ALGO DRAO RESO SASK STJO for GPS Week 1470


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