============================================================================= | ULR ANALYSIS STRATEGY SUMMARY | | (template version 2.0, 07 Aug. 2006) | ============================================================================= | Analysis Center | French Consortium of | | | University of La Rochelle, UMR 6250 LIENSs | | | and IGN's geodetic research laboratory LAREG | | | | | | Université de La Rochelle | | | Bat. ILE | | | 2 rue Olympe de Gouges | | | 17000 LA ROCHELLE | |---------------------------------------------------------------------------| | Contact people | Guy Woppelmann | | | e-mail: gwoppelm@univ-lr.fr | | | Marie-Noelle Bouin | | | e-mail: Marie-Noelle.Bouin@meteo.fr | | | Alvaro Santamaria Gomez | | | e-mail: asantamaria@fomento.es | |---------------------------------------------------------------------------| | Software used | GAMIT v. 10.21 for GPS observations processing | | | CATREF for station coordinate solutions combination | | | and alignment to ITRF2005 | |---------------------------------------------------------------------------| | GNSS system(s) | GPS | |---------------------------------------------------------------------------| | Final products | ulrWWWW7.snx weekly SINEX file | | generated for | | | GPS Week 'WWWW' | | | day of Week 'n' | | | (n=0,1,...,6) | | |---------------------------------------------------------------------------| | Preparation date | 2008-07-15 (original updated version) | |---------------------------------------------------------------------------| | Modification dates| | |---------------------------------------------------------------------------| | Effective date | 1997-01-01/2006-11-18 (GPSW 886/1401) | | for data analysis | | ============================================================================= ============================================================================= | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Preprocessing | Five sub-networks including up to 50 stations manually | | | selected with worlwide distribution. | | | Small RINEX files (less than 6 hours of observations) | | | are discarded. | |---------------------------------------------------------------------------| | Basic observable | Double-differenced carrier phase with ionosphere-free | | | combination of L1 and L2 carriers (LC or L3). Code | | | pseudoranges are used to obtain receiver clock offsets | | | and in the ambiguity resolution with the | | | Melbourne-Wuebbena widelane method. Non-redundant | | | baselines are estimated. | | |--------------------------------------------------------| | | Elevation angle cutoff: 10 degrees | | | Sampling rate: 30 seconds for cleaning | | | 5 minutes for parameter estimation | | | Weighting: at first inversion phases are weighted by | | | elevation angle, then the scatter of the | | | phase residuals are estimated by station and| | | are used in the second inversion where | | | phases are weighted by elevation angle and | | | by station. Phases are not satellite- | | | dependent weighted. | | | Code biases: C1 & P2' corrected to P1 & P2 using | | | receiver type dependent monthly tables from | | | http://www.qiub.unibe.ch/ionosphere/p1c1.dcb| |---------------------------------------------------------------------------| | Modeled | Double-differenced carrier phase with ionosphere-free | | observables | linear combination applied. | |---------------------------------------------------------------------------| |*Satellite antenna| SV-specific z-offsets & block-specific x- & y-offsets | | -center of mass | (from manufacturers) from file igs_test05.atx based on | | offsets | GFZ/TUM analyses using fixed IGb00 coordinates (see | | | IGSMail #5149, 12 May 2005). | |---------------------------------------------------------------------------| |*Satellite antenna| Block-specific nadir angle-dependent "absolute" PCVs | | phase center | applied from file igs_test05.atx; no azimuth-dependent | | corrections | corrections applied (see IGSMail #5149, 12 May 2005 | |---------------------------------------------------------------------------| |*Satellite clock | 2nd order relativistic correction for non-zero | | corrections | orbit ellipticity (-2*R*V/c) applied | |---------------------------------------------------------------------------| | GPS attitude | GPS satellite yaw attitude model: applied (Bar-Server, | | model | 1995) based on nominal yaw rates. | |---------------------------------------------------------------------------| |*RHC phase | Phase wind-up applied according to Wu et al. (1993) | | rotation corr. | | |---------------------------------------------------------------------------| |*Ground antenna | "Absolute" elevation- & azimuth-dependent (when | | phase center | available) PCVs & L1/L2 offsets from ARP applied from | | offsets & | file igs_test05.atx | | corrections | (see IGSMail #5149, 12 May 2005). | |---------------------------------------------------------------------------| |*Antenna radome | Calibration applied if given in file igs_test05.atx; | | calibrations | otherwise radome effect neglected (radome => NONE) | |---------------------------------------------------------------------------| |*Marker -> antenna| dN,dE,dU eccentricities from site logs applied to | | ARP eccentricity | compute station marker coordinates | |---------------------------------------------------------------------------| | Troposphere | Met data input: Standard temperature and | | a priori model | height dependent pressure data | | |--------------------------------------------------------| | (parameter | Zenith delay: Saastamoinen (1972) "dry" + "wet" using | | estimation is | synthesized input met data | | below) |--------------------------------------------------------| | | Mapping function: GMF (Boehm et al., 2006) dry & wet | | |--------------------------------------------------------| | | Horiz. grad. model: no a priori gradient model is used | |---------------------------------------------------------------------------| |*Ionosphere | 1st order effect: accounted for by using the ionosphere| | | free linear combination (LC or L3) | | |--------------------------------------------------------| | | 2nd order effect: no corrections applied | | |--------------------------------------------------------| | | Other effects: no other corrections applied | |---------------------------------------------------------------------------| |*Tidal |*Solid Earth tide: IERS 2003 (dehanttideinel.f routine, | | displacements | based on Chap. 7.1.2) | | |--------------------------------------------------------| | |*Permanent tide: zero-frequency contribution left in | | (IERS Conventions| tide model, NOT in site coordinates | | 2003, Ch. 4, eqn |--------------------------------------------------------| | 11 contributions)|*Solid Earth pole tide: IERS 2003; mean pole removed | | | by linear trend (Ch. 7, eqn 23a & 23b) | | |--------------------------------------------------------| | |*Oceanic pole tide: no model is applied | | |--------------------------------------------------------| | |*Ocean tide loading: IERS Conventions 2003 (updated | | | Ch. 7, 2006) using site-dependent | | | amplitudes & phases for 11 main tidal | | | constituents from the Scherneck & Bos | | | web-based Ocean Tide Loading provider | | | using the CSR4.0 ocean tide model; | | | CMC corrections applied to SP3 orbits. | | |--------------------------------------------------------| | |*Ocean tide geocenter: site-dependent coeffs corrected | | | for center of mass motion of whole | | | Earth; CMC corrections also applied | | | to SP3 orbits. | | |--------------------------------------------------------| | | Atmosphere tides: not applied | |---------------------------------------------------------------------------| |*Non-tidal | Atmospheric pressure: not applied | | loadings |--------------------------------------------------------| | | Ocean bottom pressure: not applied | | |--------------------------------------------------------| | | Surface hydrology: not applied | | |--------------------------------------------------------| | | Other effects: none applied | |---------------------------------------------------------------------------| |*Earth orientation| Ocean tidal: diurnal/semidiurnal variations in x,y, & | | variations | UT1 applied according to IERS 2003. | | |--------------------------------------------------------| | (near 12 & 24 hr | Atmosphere tidal: S1, S2, S3 tides not applied | | only; longer |--------------------------------------------------------| | period tidal | High-frequency nutation: prograde diurnal polar motion | | corrections | corrections applied using IERS routine | | should not be | (IERS 2003, Table 5.1) | | applied) |--------------------------------------------------------| | | | [NOTE: effects are included in observation model as well as in the | | transformation of orbits from inertial to terrestrial frame] | ============================================================================= ============================================================================= | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Time argument | GPS time as given by observation epochs, which is | | | offset by only a fixed constant (approx.) from TT/TDT | |---------------------------------------------------------------------------| | Inertial | Geocentric; mean equator and equinox of 2000 Jan 1.5 | | frame | (J2000.0) | |---------------------------------------------------------------------------| | Terrestrial | ITRF2005 applying the Minimal Constraint Approach on | | | the 7 transformation parameters between ITRF2005 datum | | | (comprising up to 91 IGS05 stations) and the station | | | coordinate solutions. CATREF (Altamimi et al. 2007) | |---------------------------------------------------------------------------| | Tracking | Tracking network is global: up to 225 stations, among | | network | which 160 are CGPS@TG and 91 are IGS05 stations. | | | Stations are distributed into 5 subnetworks with up to | | | 50 globally distributed stations each. | | | Subnetworks are combined (and aligned to ITRF2005) to | | | form daily solutions by applying the above mentionned | | | approach with up to 20 globally distributed IGS05 RF | | | stations in the ITRF2005 datum. | | | Daily solutions are combined and aligned to ITRF2005 | | | using the same approach to form the weekly solutions | |---------------------------------------------------------------------------| | Interconnection | Precession: IAU 1976 Precession Theory | | (EOP parameter |--------------------------------------------------------| | estimation is | Nutation: IAU 1980 Nutation Theory | | below) |--------------------------------------------------------| | | A priori EOPs: UT1 and polar motion interpolated from | | | IERS Bulletin B. | ============================================================================= ============================================================================= | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | EGM96 degree and order 9; | | (static) | C21 & S21 modeled according to polar motion variations | | | (IERS 2003, Chap. 6) | | |--------------------------------------------------------| | | GM=398600.4415 km**3/sec**2 (for TT/TDT time argument) | | |--------------------------------------------------------| | | AE = 6378136.3 m | |---------------------------------------------------------------------------| | Tidal variations |*Solid Earth tides: C20,C21,S21,C22, and S22 as in IERS | | in geopotential | (1992); n=2 order-dependent Love numbers & frequency | | | dependent corrections for 6 (2,1) tides according to | | | R. Eanes communication (1995) | | |--------------------------------------------------------| | | Ocean tides: no model applied | | |--------------------------------------------------------| | |*Solid Earth pole tide: no model applied in orbit models| | |--------------------------------------------------------| | | Oceanic pole tide: no model applied | |---------------------------------------------------------------------------| | Third-body | Sun & Moon as point masses | | forces |--------------------------------------------------------| | | Ephemeris: Generated from the MIT PEP program | | |--------------------------------------------------------| | | GM_Sun 132712440000.0000 km**3/sec**2 | | | GM_Moon 4902.7989 km**3/sec**2 | |---------------------------------------------------------------------------| | Solar radiation | A priori: nominal block-dependent constant direct | | pressure model | acceleration; Berne 9-parameter SRP model | | | with direct, y-axis, B-axis scales and once- | | | per-revolution accelerations (sine & cosine | | | terms) along each of the three axes. | | (parameter |--------------------------------------------------------| | estimation is | Earth shadow model: umbra & penumbra included | | below) |--------------------------------------------------------| | | Earth albedo: not applied | | |--------------------------------------------------------| | | Moon shadow model: umbra & penumbra included | | |--------------------------------------------------------| | | Satellite attitude: model of Bar-Sever applied (see | | | IGSMail #0591, 9 May 1994); using | | | nominal yaw rates. | | |--------------------------------------------------------| | | Other forces: none applied | |---------------------------------------------------------------------------| |*Relativitic | Dynamical correction: not applied | | effects | (see IERS 2003, Ch. 10, eqn 1) | | |--------------------------------------------------------| | | Gravitational time delay: IERS 2003, Ch. 11, eqn 17 | | | applied | |---------------------------------------------------------------------------| | 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: 15 min. | | |--------------------------------------------------------| | | Starter procedure: Runge-Kutta Formulation; initial | | | conditions taken from prior orbit solution at 12:00 | | |--------------------------------------------------------| | | Arc length: 24 hours (00:00:00 - 23:59:30 GPS time) | ============================================================================= ============================================================================= | ESTIMATED PARAMETERS (& APRIORI VALUES & CONSTRAINTS) | |---------------------------------------------------------------------------| | Adjustment | Weighted least squares method to generate loosely | | | constrained solutions and covariance matrices that | | | are passed to CATREF Software for combination and | | | alignment to the ITRF2005. | |---------------------------------------------------------------------------| | Data span | 24 hours used for each daily analysis | | | (00:00:00 - 23:59:30 GPS time) | |---------------------------------------------------------------------------| |*Station | Free network strategy (constraints to a priori values | | coordinates | are between 1 m. and 100 m., no station is fixed). All | | | station coordinates are adjusted, relative to the a | | | priori values from ITRF2005.snx | |---------------------------------------------------------------------------| | Satellite clocks | Estimated using one-way phase data aligned with | | | pseudorange. | | |--------------------------------------------------------| | | No clk files are printed out. | |---------------------------------------------------------------------------| | Receiver clocks | Estimated during clock estimation. | |---------------------------------------------------------------------------| | Orbits | Geocentric position and velocity, solar radiation | | | pressure scales and once-per-revolution perturbation | | | terms. Radiation pressure scaling factors and | | | perturbation terms are estimated for each of the | | | orthogonal directions: satellites - sun, body centered | | | Y, and orthogonal third directions estimated as | | | constant offsets for each one-day arc; plus once-per- | | | rev sine/cosine terms are estimated with apriori values| | | from the prior day. The constraints are 0.01 ppm or 20 | | | cm for initial conditions and 0.01% for the direct | | | radiation-presssure, y-bias, third axis coefficients | | | and the once-per-rev parameters. | | |--------------------------------------------------------| | | Orbits estimated per global sub-network are not | | | combined. No sp3 files are printed out. | |---------------------------------------------------------------------------| | Satellite | No attitude parameters are adjusted | | attitude | | |---------------------------------------------------------------------------| | Troposphere | Zenith delay: residual delays are adjusted for each | | | station assuming mostly dominated by | | | "wet" component and parameterized by a | | | piecewise linear, continuous model with | | | 2 hour intervals. | | |--------------------------------------------------------| | | Mapping function: GMF (Boehm et al., 2006) wet function| | | used to estimate zenith delay residuals. | | |--------------------------------------------------------| | | Zenith delay epochs: each even-integer hour | | |--------------------------------------------------------| | | Gradients: one N-S & one E-W gradient parameter for | | | each day and each station, with continuous | | | linear variation during the day; 0.03 m. at | | | 10 degree elevation 1 sigma constraint is | | | applied at all stations. Mapping function | | | from Chen and Herring (1997) is used. | |---------------------------------------------------------------------------| | Ionospheric | Not estimated | | correction | | |---------------------------------------------------------------------------| | Ambiguity | Real-valued double-differenced phase cycle ambiguities | | | adjusted except when they can be resolved confidently | | | in which case they are fixed using the Melboune- | | | Wuebbena widelane to resolve L1-L2 cycles and then | | | estimation to resolve L1 and L2 cycles. | |---------------------------------------------------------------------------| |*Earth orientation| Daily x & y pole offsets, pole-rates, UT1 and LOD. | | parameters (EOP) | x and y pole estimated as piece-wise, linear offsets. | | | A priori vaules from IERS Bulletin B. Constraints are | | | 0.001 arcsec (~3 cm) for Wobble, 0.0005 arcsec/day | | | (~1.5 cm/day) for Wobble rate, 0.00001 sec for UT1 and | | | 0.0001 sec/day for LOD. | |---------------------------------------------------------------------------| | Other | None | | parameters | | ============================================================================= ============================================================================= | REFERENCES | |---------------------------------------------------------------------------| | Altamimi, Z., X. Collilieux, J. Legrand, B. Garayt & C. Boucher, ITRF2005:| | A new release of the International Terrestrial Reference Frame based on | | time series of station positions and Earth Orientation Parameters. | | J. Geophys. Res. 112(B9), 2007. | | | | Ash, M.E., Deter,ination of Earth satellite orbits, Tech. Note 1972-5, | | Lincoln Laboratory, MIT, 19 April 1972. | | | | Bar-Sever, Y.E., New GPS attitude model, IGS Mail #591, 1995, | | http://igscb.jpl.nasa.gov/mail/igsmail/1994/msg00166.html | | | | Boehm, J., A.E. Niell, P. Tregoning, & H. Schuh, Global Mapping Function | | (GMF): A new empirical mapping function based on numerical weather | | model data, Geophys. Res. Lett., 33, L07304, doi: 10.1029/2005GL025545, | | 2006. | | | | Boehm, J., R. Heinkelmann, & H. Schuh, Short Note: A global model of | | pressure and temperature for geodetic applications, J. Geod., | | doi:10.1007/s00190-007-0135-3, 2007. | | | | Chen, G. and T.A. Herring, Effects of atmospheric azimuthal asymmetry of | | the analysis of space geodetic data, J. Geophys. Res., 102, 20, 489-20, | | 502, 1997. | | | | IERS Conventions 2003, D.D. McCarthy & G. Petit (editors), IERS Technical | | Note 32, Frankfurt am Main: Verlag des Bundesamts fuer Kartographie und | | Geodaesie, 2004. (see also updates at website) | | | | Saastamoinen, J., Atmospheric correction for the troposphere and | | stratosphere in radio ranging of satellites, in The Use of Artificial | | Satellites for Geodesy, Geophys. Monogr. Ser. 15 (S.W. Henriksen et al.,| | eds.), AGU, Washington, D.C., pp.247-251, 1972. | | | | 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, | | 91-98, 1993. | =============================================================================