============================================================================= INTERNATIONAL GPS SERVICE FOR GEODYNAMICS SOPAC Processing Strategy Summary ============================================================================= Analysis Center | Scripps Orbit and Permanent Array Center (SOPAC), | Institute of Geophysics and Planetary Physics (IGPP), | Scripps Institution of Oceanography (SIO), | University of California, San Diego (UCSD) | | 9500 Gilman Dr., San Diego, CA 92093-0225, USA | Phone: ++ 1 619 534 0229 | Fax: ++ 1 619 534 9873 ----------------------------------------------------------------------------- Contact Person(s) | Yehuda Bock e-mail: ybock@ucsd.edu | phone : ++ 1 858 534 5292 | Peng Fang e-mail: pfang@ucsd.edu | phone : ++ 1 858 534 2445 | Paul Jamason e-mail: pjamason@ucsd.edu | phone : ++ 1 858 822-4472 | Linette Prawirodirdjo e-mail: linette@ucsd.edu | phone : ++ 1 858 822-0557 ----------------------------------------------------------------------------- Software Used | GAMIT v. 10.20, GLOBK v. 5.08, developed at MIT/SIO ----------------------------------------------------------------------------- Final Products | siowwwwn.sp3 GPS ephemeris: 24 hour span, based on generated for | weekly combined solutions. GPS week 'wwww' | siowwww7.erp ERP (pole/UT1-UTC) based on weekly solution day of week 'n' | siowwww7.sum Summary of weekly solution combining both (n=0,1,...,6) | IGS global and regional solutions. | siowwww7.sum Summary of weekly solution combining both | IGS global and regional solutions. | siowwww7.snx Site position in SINEX format, based on | weekly combined solution | siowwwwn.tro Daily files of 1-h troposphere delay | estimates in SINEX format (based | on 1-day solutions). Rapid Products | sirwwwwn.sp3 Daily orbits for current-1 day. ~16 hour | delay. | sirwwwwn.erp Daily EOP for current-1 day. ~16 hour | delay. Predictions | siuwwwwn_hh.sp3 48 hour in session and 24 hour predicted | ~1 hour delay | siuwwwwn_hh.erp Subdaily (3 hour interval) EOP for the 24 | hour in session 48 hour prediction. | Note: the above ultra rapid products are | a subset of SIO hourly products ----------------------------------------------------------------------------- Preparation Date | Oct 25, 2005 ----------------------------------------------------------------------------- Modification Dates| January 11, 2004 (Change of Satellite antenna offsets; | Global Ambiquity resolution since | after 12-14-2003) ----------------------------------------------------------------------------- Effective Date for| April 4, 2005 Data Analysis | ============================================================================= ----------------------------------------------------------------------------- | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Observable | Doubly differenced, ionosphere-free combination of L1 | | | and L2 carrier phases. Pseudoranges are used only | | | to obtain receiver clock offsets and in ambiguity | | | resolution. | |---------------------------------------------------------------------------| | Data weighting | Sigma on doubly difference LC phase: Site and elevation| | | dependent based on iterated analysis. Satellite | | | dependent noise added if phase RMS to satellite if | | | RMS 10% greater than average RMS | | | Cleaning at 30-second rate. | | | Sampling rate: 2 minutes | | | Elevation angle cutoff : 10 degrees | |---------------------------------------------------------------------------| | Data Editing | Cycles slips detected and fixed (autcln Ver 3.18). | | | Unresolved cycle slips estimated in solution. Postfit | | | editing using 4 times RMS deletion. | |---------------------------------------------------------------------------| | RHC phase | Phase polarization effects applied (Wu et al, 1993) | | rotation corr. | | |---------------------------------------------------------------------------| | Ground antenna | Elevation-dependent phase center corrections are | | phase center | applied according to the model IGS_01. The corrections | | calibrations | are given relative to the Dorne Margolin T antenna. | |---------------------------------------------------------------------------| | Troposphere | A priori zenith delay: nominal constant; 2-hour piece-| | | wise linear function estimated, 1 NS and EW gradient | | | per day. | | |--------------------------------------------------------| | | Met data input: none | | |--------------------------------------------------------| | | Mapping functions: (Niell, 1996) | |---------------------------------------------------------------------------| | Ionosphere | Not modeled (ionosphere eliminated by forming the | | | ionosphere-free linear combination of L1 and L2). | |---------------------------------------------------------------------------| | Plate motions | ITRF2000 velocities | |---------------------------------------------------------------------------| | Tidal | Solid earth tidal displacement: | | displacements | constant Love number tides | | | frequency dependent radial tide (K1) | | |--------------------------------------------------------| | | Pole tide: Applied to Mean IERS pole position | | |--------------------------------------------------------| | | Ocean loading: Applied (Scherneck Model) | |---------------------------------------------------------------------------| | Atmospheric | Not applied | | loading | | |---------------------------------------------------------------------------| | Earth orientation| IERS Bulletin A plus diurnal and semidiurnal variations| | | in x,y, and UT1 models (EOP) R. Ray [1995], IERS | | | Tech. Note 21 [1996] | |---------------------------------------------------------------------------| | Satellite center | Block I x,y,z: 0.2100, 0.0000, 0.8540 m | | of mass |--------------------------------------------------------| | correction | Block II/IIA x,y,z: 0.2790, 0.0000, 1.2300 m | | |--------------------------------------------------------| | | Block IIR x,y,z: 0.0000, 0.0000, 0.0000 m | |---------------------------------------------------------------------------| | Satellite phase | Not applied | | center calibrat | | ----------------------------------------------------------------------------- | Relativity | Relativistic corrections applied | | corrections | | ----------------------------------------------------------------------------- | GPS attitude | Yaw computed using model of Bar-Sever (1996), using | | model | nominal rates or estimates supplied by JPL | ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | EGM96 degree and order 9 | | |--------------------------------------------------------| | | GM = 398600.4415 km**3/sec**2 | | |--------------------------------------------------------| | | AE = 6378.1363 km | |---------------------------------------------------------------------------| | Third-body | Sun and Moon as point masses | | |--------------------------------------------------------| | | Ephemeris: CfA PEP NBODY 740 | | |--------------------------------------------------------| | | GMsun = 132712440000 km**3/sec**2 | | |--------------------------------------------------------| | | GMmoon = 4902.7989 km**3/sec**2 | |---------------------------------------------------------------------------| | Solar radiation | A priori: nominal block-dependent constant direct | | pressure | acceleration; corrections to direct, y-axis, | | | and B-axis constant and once-per-rev terms | | | estimated (see below) (Beutler et al., 1994; | | | Springer et al. 1998) | | |--------------------------------------------------------| | | Earth shadow model: umbra and penumbra | | |--------------------------------------------------------| | | Earth's albedo: not applied | | |--------------------------------------------------------| | | Satellite attitude model not applied | |---------------------------------------------------------------------------| | Tidal forces | Solid earth tides: frequency independent Love | | | number K2= 0.300 | | |--------------------------------------------------------| | | Ocean tides: None | |---------------------------------------------------------------------------| | Relativity | Applied (IERS 1996, Chapter 11, Eqn.1) | |---------------------------------------------------------------------------| | Numerical | Adams-Moulton fixed-step, 11-pt predictor-corrector | | Integration | with Nordsieck variable-step starting procedure | | | (see Ash, 1972 and references therein) | | |--------------------------------------------------------| | | Integration step-size: 75 s; tabular interval: 900 s | | |--------------------------------------------------------| | | Arc length: 24 hours | ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | ESTIMATED PARAMETERS (A PRIORI VALUES & SIGMAS) | |---------------------------------------------------------------------------| | Adjustment | Weighted least squares plus Kalman filter | |---------------------------------------------------------------------------| | Station | Four Networks of 40 stations per network. 3-4 common | | coordinates | sites between networks. Weak constraints applied to | | | site coordinates. About 20 sites are specified for | | | for each network, based on clock type, the remaining | | | sites are dynamically selected to fill out global | | | networks. | |---------------------------------------------------------------------------| | Satellite clocks | Initial values from linar fits to Broadcast emphemeris.| | bias | Values estimated during data cleaning. Final clocks | | | generated using final orbits and weekly site | | | coordinates. | |---------------------------------------------------------------------------| | Receiver clock | Time estimated from pseudoranges. Final clocks | | bias | generated using final orbits and weekly site | | | coordinates. | |---------------------------------------------------------------------------| | Orbital | Initial Position and Velocity (IC) plus 9 radiation- | | parameters | pressure terms: constant and sin/cos once-per-rev terms| | | for a direct,y-axis, and b-axis acceleration. ICs | | | estimated each day. Radiation parameters treated as | | | random walk with process noise based on independent | | | daily estimates. | |---------------------------------------------------------------------------| | Troposphere | Peice-wise linear function in zenith delay estimated | | | once per 2-hr for each station constrained by a | | | random-walk process to 20mm/sqrt(hr); one N-S and one | | | E-W gradient parameter per day for each station, | | | constrained to 10 mm at 10 deg elevation angle | |---------------------------------------------------------------------------| | Ionospheric | Not estimated (first-order effect eliminated by linear | | correction | combination of L1 and L2 phase) | |---------------------------------------------------------------------------| | Ambiguity | Resolution attempted for all baselines but resolving | | | Melbourne-Webena Widelines for L2-L1 using pseudo- | | | ranges, and then L1 from geodetic solution using iono- | | | spheric free observable. | |---------------------------------------------------------------------------| | Earth Orient. | Pole X/Y and their rates, and UT1 rate estimated once | | Parameters (EOP) | per day. | |---------------------------------------------------------------------------| | GPS attitude | Not estimated | | model | | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Inertial | Geocentric; mean equator and equinox of 2000 Jan 1 | | | at 12:00 (J2000.0) | |---------------------------------------------------------------------------| | Terrestrial | ITRF2000, No constrained sites coordinates. Frame | | | realized be rotation and translation on to as many of | | | 99 IGb00 reference sites analyzed (Dong et al., 1998) | |---------------------------------------------------------------------------| | Interconnection | Precession: IAU 1976 | | |--------------------------------------------------------| | | Nutation: IAU 1980 | ----------------------------------------------------------------------------- REFERENCES: Ash, M. E., Determination of Earth satellite orbits, Tech. Note 1972-5, Lincoln Laboratory, MIT, 19 April 1972. Bar-Sever, Y. E., A new module for GPS yaw attitude, in Proc. IGS Workshop: Special Topics and New Directions, edit. G. Gendt and G. Dick, pp. 128-140, GeoForschungsZentrum, Potsdam, 1996. Beutler, G. (1990). Numerische Integration gewoehnlicher Differential-gleichungssysteme: Prinzipien und Algoithmen. Mitteilungen der Satelliten-Beobachtungsstation Zimmerwald, No. 23, Druckerei der Universitat Bern, 1990. Beutler, G., E. Brockmann, W. Gurtner, U. Hugentobler, L. Mervart, and M. Rothacher, Extended Orbit Modeling Techniques at the CODE Processing Center of the International GPS Service for Geodynamics (IGS): Theory and Initial Results, Manuscripta Geodaetica, 19, 367-386, 1994. Dong, D., and Y. Bock, Global Positioning System network analysis with phase ambiguity resolution applied to crustal deformation studies in California, Journal of Geophysical Research, 94, 3949-3966, 1989. Feigl, K. L., and 14 others, Space geodetic measurement of crustal deformation in central and southern California, 1984-1992, Journal of Geophysical Research, 98, 21,667-21,712, 1993. Herring, T. A., GLOBK: Global Kalman filter VLBI and GPS analysis program Version 4.17, Internal Memorandum, Massachusetts Institute of Technology, Cambridge, 1998. Herring, T. A., and D. Dong, Measurement of diurnal and semi-diurnal rotational variation and tidal parameters of the Earth, Journal of Geophysical Research, 99, 18,051, 1994. King, R. W., and Y. Bock, Documentation of the GAMIT GPS Analysis Software version 9.72, Mass. Inst. of Technol., Cambridge, 1998. McCarthy, D. D. (ed.) (1992). IERS Standards (1992). IERS Technical Note 13, Observatoire de Paris, July 1992. McCarthy, D. D. (ed.) (1996). IERS Conventions (1996). IERS Technical Note 21, Observatoire de Paris, July 1996. Niell, A. E., Global mapping functions for the atmospheric delay, J. Geophys. Res., 101, 3227-3246, 1996. Schaffrin, B., and Y. Bock, A unified scheme for processing GPS phase observations, Bulletin Geodesique, 62, 142-160, 1988. Springer, T. A., G. Beutler, and M. Rothacher, A new solar radiation pressure model for the GPS satellites, IGS Analysis Center Workshop, Darmstadt, 9-11 February 1998. Wu, J. T., S. C. Wu, G. A. Hajj, W. I. Bertiger, S. M. Lichten, Effects of antenna orientation on GPS carrier phase. Manuscripta Geodaetica 18, 1993, 91-98, 1993.