Subject: [IGSMAIL-0655] EMR IGS Pocessing Summary
From: NRCan/GSDivision
Date: Thu, 30 Jun 1994 12:15:34 PDT

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IGS Electronic Mail      Thu Jun 30 12:15:34 PDT 1994      Message Number 0655
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Author: NRCan/GSDivision
Subject: EMR IGS Pocessing Summary

Dear Colleagues,

The following AC questionnaire summarizing the EMR IGS daily processing
strategies has been submitted to IGS CB.
                           Regards,
				     J. Kouba
--------------------------------------------------------------------------

             INTERNATIONAL GPS SERVICE FOR GEODYNAMICS

        	     Analysis Centre Questionnaire

=============================================================================
ANALYSIS CENTRE   |  EMR, Geodetic Survey Division, Natural Resources Canada 
		  |  (NRCan), (Formerly EMR Canada)
                  |  615 Booth Street, Ottawa, Canada, K1A 0E9
-----------------------------------------------------------------------------
CONTACT PERSON(S) |  Pierre Tetreault ([email-masked]), ph.(613) 9922218
                  |  Jan    Kouba     ([email-masked]) , ph.(613) 9922678
----------------------------------------------------------------------------- 
SOFTWARE USED     |  GIPSY/OASIS II (April 92 version), developed by JPL
-----------------------------------------------------------------------------
IGS PRODUCTS      | EMR0www0-6.sp3 GPS ephemeris/clock files in 7 daily files
GENERATED FOR     |                at 15 min intervals in sp3 format,
GPS WEEK 'www'    |                including accuracy codes, which are assigned 
                  |                25 cm nominally, and adjusted upward when
                  |                indicated by orbit corrections
                  | EMR0www7.erp   ERP (pole, UT1-UTC, LOD) solutions
                  | EMR0www7.sum   Processing summary. Includes sat./station
                  |                daily statistics.
-----------------------------------------------------------------------------
PREPARATION DATE  |  June 30, 1994
=============================================================================

----------------------------------------------------------------------------- 
|                     MEASUREMENT MODELS                                    |
|---------------------------------------------------------------------------|
| Preprocessing    | single station type, using L1-L2 phase and pseudorange |
|                  | data, editing most cycle slips, computes smoothed      |
|                  | pseudoranges at requested intervals (7.5min),          | 
|                  | introduces and initilizes real phase ambiguities       | 
|---------------------------------------------------------------------------| 
| Basic observable | carrier phase and smoothed pseudo-range                |
|                  |--------------------------------------------------------|
|                  | elevation angle cutoff : 15 degrees                    |
|                  | sampling rate          : 7.5 minutes                   |
|                  | weighting              : exponentional, station/satell.|
|                  |                          specific.                     |
|                  | Rejection criteria     : 5 (aposteriori) sigmas        |
|---------------------------------------------------------------------------| 
| Modelled         | undifferenced, corrected for ionosphere (L3, P3),      |
| observable       | CA pseudoranges corrected for CA-P1 biases whenever    |
|                  | applicable                                             | 
|---------------------------------------------------------------------------| 
| RHC Polar. phase | not applied                                            |
| rotation corr.   |                                                        |
|---------------------------------------------------------------------------|
| Ground antenna   | not applied                                            |
| phase centre cal.|                                                        |
|---------------------------------------------------------------------------|
| Troposphere      | Zenith delay: treated as a random walk process         |
|                  |--------------------------------------------------------| 
|                  | Mapping function: Lanyi mapping function               |
|---------------------------------------------------------------------------| 
| Ionosphere       | not modelled (ionospheric effects accounted for by     |
|                  | dual frequency observations, see above)                |
|---------------------------------------------------------------------------| 
| Plate motions    | ITRF 92 station velocities fixed  (see IGSMAIL#421)    |
|---------------------------------------------------------------------------| 
| Tidal            | Solid earth tidal displacement: Williams model         | 
| displacements    |--------------------------------------------------------| 
|                  | Pole tide: not applied                                 |
|                  |--------------------------------------------------------| 
|                  | Ocean loading: Pagiatakis (1982) model                 |
|---------------------------------------------------------------------------|
| Atmospheric load.| not applied                                            |
|---------------------------------------------------------------------------| 
| Satellite center | Block I x,y & z: (0.210, 0, 0.854m)                    |
| of mass          |--------------------------------------------------------|
| correction       | Block II/IIA x,y & z :(0.279, 0, 0.952m)               |
|---------------------------------------------------------------------------| 
| Satellite phase  | not applied                                            |
| centre calibrat. |                                                        |
----------------------------------------------------------------------------

----------------------------------------------------------------------------- 
|                           ORBIT MODELS                                    |
|---------------------------------------------------------------------------| 
| Geopotential     | GEM T3 + C21+S21 model up to degree and order 8        |
|                  |--------------------------------------------------------| 
|                  | GM=398600.4415  km**3/sec**2                           |
|                  |--------------------------------------------------------| 
|                  | AE = 6378.137 km                                       |
|---------------------------------------------------------------------------| 
| Third-body       | Sun, Moon and planets regarded as point masses         |
|                  |--------------------------------------------------------| 
|                  | ephemeris: JPL DE200                                   |
|                  |--------------------------------------------------------| 
|                  | GMsun = 132712439935.4842 km**3/sec**2                 |
|                  |--------------------------------------------------------| 
|                  | GMmoon = 4902.7991 km**3/sec**2                        |
|---------------------------------------------------------------------------| 
| Solar radiation  | direct radiation: ROCK4 and ROCK42T models for         |
| pressure         |                   Block I and II satellites, resp.     |
|                  | area, specularities and reflectivity used: see         |
|                  | Tables 1,2, (Fliegel and Gallini, 1992, JGR(97)B1,p562)|
|                  |                                                        |
|                  | satellite masses used: PRN 12    519.8kg               |
|                  |  PRN 01    880.0kg     PRN 21-22 883.9                 |
|                  |      02    878.2           23    972.9                 |
|                  |      14    887.4           24-31 880.0                 |
|                  |      15    885.9           04-06 972.9                 |
|                  |      16-19 883.2           07    883.9                 |
|                  |      20    887.4           09    972.9                 |
|                  |--------------------------------------------------------| 
|                  | x,z, scale and y- radiation biases: taken into account |
|                  |--------------------------------------------------------| 
|                  | Earth shadow model includes: penumbra and atmospheric  |
|                  | refraction/attenuation effects                         |
|                  |--------------------------------------------------------| 
|                  | reflection radiation: not applied                      |
|                  |--------------------------------------------------------|
|                  | new GPS satellite attitude model: not applied          |
|---------------------------------------------------------------------------| 
| Tidal forces     | solid earth tides: frequency independent Love's        |
|                  | number K2= 0.300                                       |
|                  |--------------------------------------------------------| 
|                  | Ocean tides: UT CSR model from Schwiderski             |
|---------------------------------------------------------------------------| 
| Relativity       | applied (only periodic term)                           |
|---------------------------------------------------------------------------| 
| Numerical        | variable (high) order Adams predictor-corrector        | 
| integration      | with direct integration of second-order equations      |
|                  |--------------------------------------------------------|
|                  | integration step : variable (typically < 1000s)        |
|                  |--------------------------------------------------------| 
|                  | starter procedure: Runge-Kutta                         |
|                  |--------------------------------------------------------| 
|                  | arc length       : 24 hours                            |
----------------------------------------------------------------------------- 

----------------------------------------------------------------------------- 
|                    ESTIMATED PARAMETERS (APRIORI VALUES & SIGMAS)         |
|---------------------------------------------------------------------------| 
| Adjustment       | square-root information filter (SRIF) [Bierman, 1977]  |
|---------------------------------------------------------------------------| 
| Station          | 13 stations constrained to the ITRF92 positions (using |
| coordinates      | ITF92 sigmas) as given in IGSMAIL#430, the remaining   |
|                  | stations estimated (50m apriori sigmas). The ITRF92    |
|                  | velocities are used for daily coordinates updates.     |
|                  |--------------------------------------------------------|
|                  | In POSTPROCESSING and station combination,             |
|                  | Apriori station constraints are rigorously removed     |
|                  | for input into combined station solutions (adding      |
|                  | the reduced normal matrices)                           | 
|---------------------------------------------------------------------------| 
| Satellite clock  | modelled as white noise process and solved for at each |
| bias             | epoch. ( 1ms appriori sigmas, apriori values from      |
|                  | broadcast message). Thus each epoch solution is        |
|                  | independent and based on both phase and pseudorange    |
|                  | observations. WARNING: no L1-L2 satellite calibration  |
|                  | applied, so the satellite clocks include the L1-L2     |
|                  | calibration delays                                     |
|---------------------------------------------------------------------------| 
| Receiver clock   | a white noise process (with large 1 s apriori sigmas,  |
| bias             | apriori values from preprocessing). One Hydrogen Maser |
|                  | clock fixed and used as a time reference, usually ALGO.|
|                  | Thus each epoch solution is                            |
|                  | independent and based on both phase and pseudorange    |
|                  | observations. WARNING: no P1-P2 receiver  calibration  |
|                  | applied, so the receiver clocks include the P2-P1 cal. |
|                  | delays, whenever applicable (i.e. Rogues SNR8-800)     |
|---------------------------------------------------------------------------| 
| Orbital          | initial position and velocity, solar radiaton pressure |
| parameters       | scales in x, z and y-bias considered                   | 
|                  | constant through the orbital arc. Orbit states modelled|
|                  | as a random walk process between adjacent 24h orbit    |
|                  | arcs.Apriori orbits, extrapolated from previous arc are|
|                  | assigned the following stochastic sigmas               |
|                  | (for convenience Keplerian elements are used, then     |
|                  | transformed into the x,y,z frame of reference used for |
|                  | processing):                                           |
|                  | semi-major axis a  - .20m/sqrt(day)                    |
|                  | eccentricity    e  - .25m/sqrt(day)                    |
|                  | inclin., node i,RA - .12m/sqrt(day)                    |
|                  | perigee, M.A  p,MA - .33m/sqrt(day)                    |
|                  | velocities DX,DY,DZ- .0005m/s/sqrt(day)                |
|                  | x, z scales        - .05            (white noise)      |
|                  | y bias             - .5d-09 m/s**2  ( "     "   )      |
|---------------------------------------------------------------------------| 
| Troposphere      | estimated as a random walk (within a 24h)  with about  |
|                  | 0.01m/sqrt(hr) sigma. All stations are assigned        |
|                  | the same apriori values of 2.0m  with 0.4m apriori     |
|                  | sigmas to initiate the random walk process.            |
|---------------------------------------------------------------------------| 
| Ionospheric      | not estimated, L1 & L2 used for the 1st order          |
| correction       | corrections                                            |
|---------------------------------------------------------------------------| 
| Ambiguitiies     | real ,estimated as needed (from preprocessing), with   |
|                  | apriori values from pseudorange observation preprocess.|
|                  | apriori sigmas 3.0D08m                                 |
|---------------------------------------------------------------------------| 
| ERP              | x & y pole, UT1-UTC and LOD. Current IERS Bulletin A,  |
|                  | (updated every two weeks only) and used as apriori.    |
|                  | Constant during a 24h period, solutions refer to       |
|                  | 12:00h UT.                                             |
|		   | Apriori sigmas used:                                   |
|                  | x,y pole x, y  - 100mas;  UT1-UTC - 6.8ms              |
|                  | LOD            - 86000 ms/day.                         |
|                  |                                                        |
|                  | Note: In POSTPROCESSING the ERP and/or station apriori |
|                  | sigmas can be rigorously removed or changed            | 
|---------------------------------------------------------------------------|
| Other            | C1-P1 Pseudorange biases periodically checked and      |
| parameters       | updated as necessary from postfit pseudorange residuals|
----------------------------------------------------------------------------- 

----------------------------------------------------------------------------- 
|                       REFERENCE FRAMES                                    |
|---------------------------------------------------------------------------| 
| Inertial         | Geocentric; mean equator and equinox of 2000 Jan 1.5   |
|                  | (J2000.0)                                              |
|---------------------------------------------------------------------------| 
| Terrestrial      | ITRF92 reference frame realized through the set of 13  |
|                  | station coordinates and velocities as given in IGSMAIL#|
|                  | 430 as well as the antenna offsets for the above       |
|                  | stations as given in /igscb/station/tie/localtie.tab   |
|                  | which is available from IGS CB (sideshow.jpl.nasa.gov) |
|---------------------------------------------------------------------------| 
| Interconnection  | Precession: IAU 1976 Precession Theory                 | 
|                  |--------------------------------------------------------|
|                  | Nutation  : IAU 1980 Nutation Theory                   |
|                  |--------------------------------------------------------| 
|                  | Relationship between UT1 and GMST: Aoki et al. (1982)  |
|                  |--------------------------------------------------------| 
|                  | ERP interpolated from IERS Bulletin A (updated every   |
|                  | two weeks. No celestial pole corrections)              |
|                  |--------------------------------------------------------| 
|                  | Tidal variations in UT1: applied (periods > 5.8days )  |
----------------------------------------------------------------------------- 

References:
Aoki, S., Guinot, B., Kaplan, G.H., Kinoshita, H., McCarthy, D.D.,
Seidelman, P.K. (1982). "The New Definition of Universal Time", Astron. 
Astrophys., 105, pp. 359-361.

Bierman, G.J. (1977). "Factorization methods for discrete sequential
estimation, Academic Press, San Diego, Calif.

 Lichten, S. and J. S. Border (1987). "Strategies for High-Precision 
Global Positioning System Orbit Determination."  Journal of Geophysical 
Research, Vol. 92, NO. B12, pp. 12751-12762.

Lichten, S. M. (1990). "Estimation and Filtering for high-precision GPS 
positioning applications."   Manuscripta Geodeatica, Vol. 15, 
pp. 159-176.

Tralli, D. M. and S. M. Lichten (1990). "Stochastic estimation of 
tropospheric path delays in global positioning system geodetic measurements."
 Bulletin  Geodesique, Vol. 64, No. 2. pp. 127-159.

Sovers and Border (1990). Observation model and parameter partials for the
JPL geodetic modeling software "GPSOMC". JPL Publication 87-21, Rev. 2, 
JPL, Pasadena, CA, USA.

Pagiatakis, S.D.(1982). Ocean loading, body tides and polar motion effects on
very long baseline interferometry. UNB Technical rep. No. 2, Dept. of 
Surv. Engineering, Univ. of New Brunswick, Fredericton, N.B.

Kouba,J., P. Tetreault, R. Ferland and F. Lahaye (1993). IGS data processing
at the EMR Master Control System Centre, Proceedings of the 1993 IGS Workshop,
held at Univ. of Berne, Switzerland, March 1993, pp.123-132.

[Mailed From: Jan Kouba <[email-masked]>]