Subject: [IGSMAIL-3708]: NRCan Updated Analysis Information Table
From: Pierre Tetreault <[email-masked]>
To: [email-masked] (IGSMailbox)
Date: Wed, 23 Jan 2002 18:43:06 GMT

******************************************************************************
IGS Electronic Mail      23 Jan 10:43:09 PST 2002      Message Number 3708
******************************************************************************

Author: NRCan / P. Tetreault

Dear colleagues,

Please find attached a copy of the updated NRCan (EMR) analysis center analysis
information table recently submitted to the IGS Central Bureau
(ftp://igscb.jpl.nasa.gov/igscb/center/analysis).

Pierre Tetreault
Geodetic Survey Division
Natural Resources Canada

=============================================================================

                         INTERNATIONAL GPS SERVICE 

                   EMR (NRCan) Processing Strategy Summary

=============================================================================
ANALYSIS CENTRE   |  EMR, Geodetic Survey Division, Natural Resources Canada
                  |  (NRCan), (Formerly EMR Canada)
                  |  615 Booth Street, Ottawa, Canada, K1A 0E9
----------------------------------------------------------------------------
CONTACT PERSON(S) |  Caroline Huot(1)    e-mail: [email-masked]
		  |                      phone: 613-996-4914
                  |  Brian Donahue(1)    e-mail: [email-masked]
		  |                      phone: 613-947-4246
                  |  Pierre Tetreault(1) e-mail: [email-masked]
		  |                      phone: 613-992-2218
                  |  Yves Mireault(2)    e-mail: [email-masked]
		  |                      phone: 613-947-7937
		  |
		  |  (1) for final and rapid products 
		  |  (2) for ultra-rapid products 
----------------------------------------------------------------------------
SOFTWARE USED     |  GIPSY/OASISII Version 2.6, developed by JPL (final/rapid)
                  |  Bernese Version 4.2, developed by U of Berne, (ultra-rapid)
-----------------------------------------------------------------------------
FINAL PRODUCTS    | emrwwww0-6.sp3 GPS ephemeris/clock files in 7 daily files
GENERATED FOR     |                at 15 min intervals in sp3 format,
GPS WEEK 'wwww'   |                including orb. acc. codes (2* formal sigmas
                  |                assigned nominally) adjusted as needed
                  |                when indicated by orbit corrections
                  | emrwwww7.erp   ERP (pole & rates, UT1-UTC, LOD) solutions
                  | emrwwww0-6.clk Satellite and receiver clock estimates   
                  |                at 5-min intervals in RINEX format       
		  | emrwwww0-6.tro Ground site troposphere estimates
                  | emrwwww7.sum   Processing summary. Includes sat./station
                  |                daily statistics (phase/pseudorange rms),
                  |                daily station clock solutions.
                  | emrwwww7.snx   weekly combination of loose station/EOP
                  |                daily solutions in SINEX format
                  |
RAPID PRODUCTS    | emrwwww0-6.sp3 same as above only generated within a 17h
GENERATED DAILY   | emrwwww0-6.erp delay and contributed only to the IGS
                  |                Rapid (IGR) combinations (delay <=17h)
                  | emrwwww0-6.clk Satellite and receiver clock estimates   
                  |                at 5-min intervals in RINEX format       
                  |   
ULTRA-RAPID       | emuwwww0-6_hh.sp3 GPS ephemeris files for 24-hr observed 
PRODUCTS          |                   and 24-hr predicted spans twice daily    
GENERATED         |                   where the middle epoch is 00:00 UTC and  
TWICE-DAILY       |                   12:00 UTC, tabulated at 15-min intervals 
                  |                   in sp3 format, and including estimated   
                  |                   accuracy codes                           
                  | emuwwww0-6_hh.erp ERP (pole, UT1-UTC estimates)
                  |                   for 24-hr observed and 
                  |                   24-hr predicted spans twice daily where  
                  |                   the middle epoch is 00:00 UTC and        
                  |                   12:00 UTC.  Contributed only to the IGS 
                  |                   ULTRA-Rapid (IGR) combinations
-----------------------------------------------------------------------------
PREPARATION DATE  |  January 21, 2002
----------------------------------------------------------------------------
EFFECTIVE DATE FOR|  November 4, 2001 - EMR final solutions
DATA ANALYSIS     |  December 2, 2001 - EMR rapid solutions
=============================================================================

*****************************************************************************
*****************************************************************************
Note:  All the information to follow applies only to the rapid and final EMR
       products. More information on ultra-rapid products will be added at 
       some future date.
*****************************************************************************
*****************************************************************************

-----------------------------------------------------------------------------
|                     MEASUREMENT MODELS                                    |
|---------------------------------------------------------------------------|
| Preprocessing    | single station type, using L1-L2 phase and pseudorange |
|                  | data, editing most cycle slips, computes smoothed      |
|                  | pseudoranges at requested intervals (5min),            |
|                  | introduces and initializes real phase ambiguities      |
|---------------------------------------------------------------------------|
| Basic observable | carrier phase and smoothed pseudo-range                |
|                  |--------------------------------------------------------|
|                  | elevation angle cutoff : 15 degrees                    |
|                  | sampling rate          : 5 minutes                     |
|                  | weighting              : exponential, station          |
|                  |                                         specific.      |
|                  |                        : nominally 1cm carrier phase   |
|                  |                                    1m  pseudorange     |
|                  | Rejection criteria     : 5 (aposteriori) sigmas        |
|---------------------------------------------------------------------------|
| Modelled         | undifferenced, corrected for ionosphere (L3, P3),      |
| observable       | P2'=C1+(P2-P1) pseudoranges converted to be consistent |
|                  | with non-cross-correlation P2 pseudoranges.            |
|---------------------------------------------------------------------------|
| RHC Polar. phase | applied (Wu et al., 1993)                              |
| rotation corr.   |                                                        |
|---------------------------------------------------------------------------|
| Ground antenna   | not applied                                            |
| phase centre cal.|                                                        |
|---------------------------------------------------------------------------|
| Troposphere      | A priori zenith : constants  "dry" + "wet"  specific   |
|                  |                   for each station                     |
|                  |--------------------------------------------------------|
|                  | Mapping function: Niell                                |
|                  |                                                        |
|                  |--------------------------------------------------------|
|                  | Met. data input : None                                 |
|                  |--------------------------------------------------------|
|                  | Estimation      : total zenith, horizontal delay       |
|                  |                   gradients: modeled as random         |
|                  |                   walk process (~0.3cm/sqrt(h))        |
|---------------------------------------------------------------------------|
| Ionosphere       | not modelled (ionospheric effects accounted for by     |
|                  | dual frequency observations, see above)                |
|---------------------------------------------------------------------------|
| Plate motions    | IGS00 station velocities fixed                         |
|---------------------------------------------------------------------------|
| Tidal            | Solid earth tidal displacement:  Williams model        |
| displacement     |                                                        |
|                  |--------------------------------------------------------|
|                  | Pole tide                     :  applied               |
|                  |--------------------------------------------------------|
|                  | Ocean loading                 :  Scherneck model [1991]|   
|---------------------------------------------------------------------------|
| Atmospheric load.| not applied                                            |
|---------------------------------------------------------------------------|
| Earth Orientation| Tidal UT1 (>5day) : modelled                           |
| models (EOP)     | ~24h & ~12h EOP   : applied (1996 IERS Standards)      |
|                  | Due to an oversight, the subdaily effects were not     |
|                  | included in the transformation of the orbits from the  |
|                  | inertial to Earth-fixed frames until 1 July 2001.      |
|---------------------------------------------------------------------------|
| Satellite center | Block II/IIA x,y & z : (0.279 m , 0 , 1.023 m)         |
| of mass          |--------------------------------------------------------|
| correction       | Block IIR x,y & z : (0 , 0 , 0)                        |
|---------------------------------------------------------------------------|
| Satellite phase  | not applied                                            |
| centre calibrat. |                                                        |
|---------------------------------------------------------------------------|
| Relativity       | Periodic, -2(R.V/c) : applied                          |
| corrections      | Grav. bending       : applied (IERS '92, p.134, eqn 37)|
|                  | Dynamical           : not applied (IERS '92,p.123,eqn1)|
|---------------------------------------------------------------------------|
| GPS Attitude     | GPS satellite attitude model (IGSMAIL#591) : kinematic |
| model            | measurement corrections based on apriori yaw rates     |
|                  | (made available by JPL)                                |
-----------------------------------------------------------------------------

-----------------------------------------------------------------------------
|                           ORBIT MODELS                                    |
|---------------------------------------------------------------------------|
| Geopotential     | JGM3 degree and order 12                               |
|                  |             (C21, S21 modeled acc. to polar motion )   |
|                  |--------------------------------------------------------|
|                  | GM=398600.4415  km**3/sec**2                           |
|                  |--------------------------------------------------------|
|                  | AE = 6378.137 km                                       |
|---------------------------------------------------------------------------|
| Third-body       | Sun and Moon regarded as point masses                  |
|                  |--------------------------------------------------------|
|                  | ephemeris: JPL DE405S                                  |
|                  |--------------------------------------------------------|
|                  | GMsun = 132712439935.4842 km**3/sec**2                 |
|                  |--------------------------------------------------------|
|                  | GMmoon = 4902.7991 km**3/sec**2                        |
|---------------------------------------------------------------------------|
| Solar radiation  | direct radiation:  GSPM_EPS model of Bar-Sever (1997)  |
| pressure         |                                                        |
|                  |--------------------------------------------------------|
|                  | x,z, scale and y- radiation biases: taken into account |
|                  |--------------------------------------------------------|
|                  | Earth shadow model includes: penumbra and atmospheric  |
|                  | refraction/attenuation effects                         |
|                  | reflection radiation: not applied                      |
|---------------------------------------------------------------------------|
| Tidal forces     | solid earth tides: frequency independent Love's        |
|                  | number K2= 0.300                                       |
|                  |--------------------------------------------------------|
|                  | Ocean tides: UT CSR model from Schwiderski             |
|---------------------------------------------------------------------------|
| 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 (rapid) / 30 hours (final) |
-----------------------------------------------------------------------------

-----------------------------------------------------------------------------
|                    ESTIMATED PARAMETERS (APRIORI VALUES & SIGMAS)         |
|---------------------------------------------------------------------------|
| Adjustment       | square-root information filter (SRIF) [Bierman, 1977]  |
|---------------------------------------------------------------------------|
| Station          | 13 stations constrained to the ITRF94 positions (using |
| coordinates      | ITF94 sigmas) as given in the IERS TN #20: TROM, MADR  |
|                  | KOSG,WZTR,HART,FAIR,KOKB,YELL,ALGO,GOLD,SANT,TIDB,YAR1;|
|                  | other stations estimated (50m apriori sigmas). The     |
|                  | ITRF94 vel. are used for daily coordinates updates.    |
|                  |                                                        |
|                  | On 05 July 1998, ref. frame was updated to ITRF96      |
|                  | using ITRF96_IGS_RS47.SNX for apriori values.  A       |
|                  | fiducial-free approach (loose 10m constraints on a     |
|                  | subset of IGS 47 fiducial stations) was also adopted   |
|                  | at the same time for the final products.               |
|                  |                                                        |
|                  | On 01 August 1999, ref. frame was updated to ITRF97    |
|                  | using ITRF97_IGS_RS51.SNX for apriori values.          |
|                  |                                                        |
|                  | On 04 June 2000 the reference frame was changed to the |
|                  | the IGS internal realization of ITRF97 (IGS97) for     |
|                  | for apriori values.                                    |
|                  |                                                        |
|                  | On 02 Dec 2001 the reference frame was changed to the  |
|                  | IGS internal realization of ITRF2000 (IGS00) for       |
|                  | apriori values.                                        |
|                  |--------------------------------------------------------|
|                  | In POSTPROCESSING and station combination,             |
|                  | Apriori station constraints are rigorously removed     |
|                  | for input into combined station (SNX) solutions (adding|
|                  | the reduced normal matrices);including vel. & EOP      |
|---------------------------------------------------------------------------|
| Satellite clock  | modelled as white noise process and solved for at each |
| bias             | epoch. ( 1ms apriori 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.               |
|---------------------------------------------------------------------------|
| Orbital          | initial position and velocity are considered constant  |
| parameters       | through the orbital arc;  stochastic y-bias and solar  |
|                  | pressure scales (x,z), steady state sigma of 1% and    | 
|                  | correlation time of 4 hrs solved for hourly.           | 
|                  | Orbit states are 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) : .10m/sqrt(day)                    |
|                  | eccentricity   (e) : .12m/sqrt(day)                    |
|                  | inclin., node(i,RA): .06m/sqrt(day)                    |
|                  | perigee, M.A (p,MA): .16m/sqrt(day)                    |
|                  | velocity (DX,DY,DZ): .00005m/s/sqrt(day) non eclipsing |
|                  |                      .0001m/s/sqrt(day)  eclipsing     |
|---------------------------------------------------------------------------|
| Troposphere      | estimated as a random walk with about                  |
|                  | 0.03m/sqrt(hr) sigma. Each station is assigned         |
|                  | specific apriori values for dry/wet z. delay with 0.4m |
|                  | apriori sigmas to initiate the random walk process.    |
|---------------------------------------------------------------------------|
| Ionospheric      | not estimated, L1 & L2 used for the 1st order          |
| correction       | corrections                                            |
|---------------------------------------------------------------------------|
| Ambiguities      | real ,estimated as needed (from preprocessing), with   |
|                  | apriori values from pseudorange observation preprocess.|
|                  | apriori sigmas 3.0D08m                                 |
|                  |--------------------------------------------------------|
|                  | Average of fixed ambiquities (%):  0%                  |
|---------------------------------------------------------------------------|
| Earth Orient.    | PM x, y, UT1-UTC and LOD, PM x, y rates. Apriori values|
| Parameters (EOP) | obtained from a polynomial fit of the 3 preceding days,|
|                  | augmented by the IERS diurnal/semidiur EOP model. All  |
|                  | reported EOP solutions DO NOT include the diurnal/semi-|
|                  | diurnal EOP model, thus the EOP solutions correspond to|
|                  | 24h averages, i.e. valid from 0 to 24h of the current  |
|                  | day.                                                   |
|                  | Apriori sigmas used:                                   |
|                  | PM x, y        :   100 mas                             |
|                  | PM x, y rates  :     5 mas/day                         |
|                  | UT1-UTC        :     7 ms                              |
|                  | LOD            : 86400 ms/day.                         |
|                  | NOTE: In POSTPROCESSING the EOP and/or station apriori |
|                  | sigmas can be rigorously removed or changed            |
|                  | WARNING: UT1-UTC and LOD are estimated separately, thus|
|                  | are not related by integration.                        |
|                  | -------------------------------------------------------|
|                  | Reported EOP    | PM x, y, PM x,y rates, UT1-UTC, LOD  |
|                  | (valid 0-24h)   | compatible with SNX solutions        |
|                  |--------------------------------------------------------|
|                  | Diurnal/semidiur|  No (equivalent to a 24h average EOP)|
|                  | EOP model added |                                      |
|                  | to reported EOP |                                      |
|---------------------------------------------------------------------------|
| GPS satellite    | yaw rates (estimated/nominal): not estimated; nominal  |
| attitude model   |                                yaw rates (by JPL)      |
-----------------------------------------------------------------------------

-----------------------------------------------------------------------------
|                       REFERENCE FRAMES                                    |
|---------------------------------------------------------------------------|
| Inertial         | Geocentric; mean equator and equinox of 2000 Jan 1.5   |
|                  | (J2000.0)                                              |
|---------------------------------------------------------------------------|
| Terrestrial      | ITRF2000 reference frame realized through the set of   |
|                  | up to 38 stations coordinates and velocities as given  |
|                  | the IGS00  (the IGS realization of ITRF2000) and 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)                         |
|                  |--------------------------------------------------------|
|                  |Nominal scale   | SI = [1 + (0.7ppb)] * EMR             |
|                  |to SI (ITRF)    | due to use of TT(TAI) time            |
|                  |(IAU '91/'94)   |                                       |
|                  |--------------------------------------------------------|
|                  |ITRF (SP3)orbits| in GPS time; diur/semidiur EOP model  |
|                  |                | (IERS 96 ) included                   |
|---------------------------------------------------------------------------|
| Interconnection  | Precession: IAU 1976 Precession Theory                 |
|                  |--------------------------------------------------------|
|                  | Nutation  : IAU 1980 Nutation Theory + CP corr.(Bull.A)|
|                  |--------------------------------------------------------|
|                  | Relationship between UT1 and GMST: Aoki et al. (1982)  |
|                  |--------------------------------------------------------|
|                  | EOP: solved  PM x,y, PM x,y rates, UT1, LOD, augmented |
|                  | with diurnal/semidiurnal EOP. The Celestial Pole (CP)  |
|                  | from the current IERS Bull A are used)                 |
|                  |--------------------------------------------------------|
|                  | Tidal variations in UT1: periods > 5.8days  modelled   |
|                  |                    and included (UT1-UTC) solutions    |
-----------------------------------------------------------------------------

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.

IERS (1992) Standards, IERS Technical Note 13, Observatoire de Paris,
(edited by McCarthy, D.)

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.

Wu J.,T. et al., (1993). "Effects of Antenna Orientation on GPS Phase,
Manuscripta Geodetica (1993)", 18, pp. 91-98.
--

Geodetic Survey of Canada
Ottawa, Ontario, Canada
Internet: [email-masked]