============================================================================= | GFZ TIGA ANALYSIS STRATEGY SUMMARY | ============================================================================= | ANALYSIS CENTRE | Helmholtz Centre Potsdam | | | GFZ German Research Centre for Geosciences | | | Telegrafenberg | | | D-14473 Potsdam | | | Germany | | | | | | phone: +49(0)-331-288-0 | | | website: www.gfz-potsdam.de | |---------------------------------------------------------------------------| | Contact people | Sergei Rudenko | | | e-mail: rudenko@gfz-potsdam.de | | | phone: +49(0)-8153-28-1578 | | | Gerd Gendt | | | e-mail: gend@gfz-potsdam.de | | | phone: +49(0)-331-288-1114 | | | Michael Daehnn | | | e-mail: daen@gfz-potsdam.de | | | phone: +49(0)-331-288-1170 | |---------------------------------------------------------------------------| | Software used | EPOS.P.V2 developed at GFZ | |---------------------------------------------------------------------------| | GNSS system(s) | GPS | |---------------------------------------------------------------------------| | Final products | GTZwwww7.snx weekly SINEX file | | generated for | | | GPS Week 'wwww' | | | day of Week 'n' | | | (n=0,1,...,6) | | | | | |---------------------------------------------------------------------------| | Preparation date | January 7, 2009 | |---------------------------------------------------------------------------| | Modification dates| - | |---------------------------------------------------------------------------| | Effective date | January 21, 2008 (version 1 reprocessing campaign) | | for data analysis | | ============================================================================= ============================================================================= | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Preprocessing | Rapid: TurboEdit (Blewitt,1990) based on undifferenced | | | observations | | | | | | Final: PPP-cleaning of phase data using rapid products | |---------------------------------------------------------------------------| | Basic Observable | carrier phases and pseudo-ranges | | |--------------------------------------------------------| | | elevation angle cutoff: 7 degrees | | | sampling rate: 5 minutes | | | weighting: elev.dep. weighting with unit weight | | | until 30 deg, 1/2sin(e) below | | | deweighting: - | | | smoothing: - | | | code biases: - C1 & P2' corrected to P1 & P2 using | | | cc2noncc tool depending on receiver type | | | (IGS mail #3737, 13 Feb 2002) | | | phase biases: - correction of receiver clock msec- | | | jumps (Zhang et al. 2007) | |---------------------------------------------------------------------------| | Modeled | undifferenced observables, corrected for 1st order | | observables | effect by forming ionosphere-free linear combination | |---------------------------------------------------------------------------| |*Satellite antenna| SV-specific z-offsets & block-specific x- & y-offsets | | -center of mass | (from manufacturers) from file igs05_wwww.atx based on | | offsets | GFZ/TUM analyses using fixed ITRF2005 coordinates | | | (see IGS Mail #5189, 17 Aug 2005) | |---------------------------------------------------------------------------| |*Satellite phase | block-specific nadir angle-dependent absolute PCVs | | corrections | from IGS antenna model igs05_wwww.atx; no azimuth- | | | dependent corrections applied | | | (see IGS Mail #5189, 17 Aug 2005) | |---------------------------------------------------------------------------| |*Satellite clock | 2nd order relativistic correction for non-zero orbit | | corrections | ellipticity (-2*R*V/c) applied (see GPS interface | | | specification IS-GPS200-D) and gravitational bending | | | (based on IERS 2003, Ch. 11, Eq. 17) | |---------------------------------------------------------------------------| | GPS Attitude | GPS satellite yaw attitude model: applied based on | | model | nominal yaw rates (Bar-Sever, 1996) | |---------------------------------------------------------------------------| |*RHC phase | phase wind-up applied (Wu et al., 1993) | | rotation corr. | | |---------------------------------------------------------------------------| |*Ground antenna | absolute IGS antenna model igs05_wwww.atx | | phase center | (see IGSMail #5149, 12 May 2005) | | offsets and | | | corrections | | |---------------------------------------------------------------------------| |*Antenna radome | calibration applied if given in file igs05_wwww.atx; | | calibrations | otherwise radome effect neglected and instead standard | | | antenna model (radome => NONE) is used | |---------------------------------------------------------------------------| |*Marker -> antenna| dN, dE, dU eccentricities from site logs applied to | | ARP eccentricity | compute station marker coordinates | |---------------------------------------------------------------------------| | Troposphere | met data input : empirical model Global Pressure and | | a priori model | Temperature (GPT) according to Boehm et al. 2007; | | | relative humidity set to 60 % for all sites | | |--------------------------------------------------------| | | zenith delay: Saastamoinen 'dry' and 'wet' | | |--------------------------------------------------------| | | mapping function: Global Mapping Functions (GMF) | | | (Boehm et al., 2006) | | |--------------------------------------------------------| | | horiz. grad. model: not applied | |---------------------------------------------------------------------------| |*Ionosphere | 1st order effect: ionospheric effects accounted for by | | | dual frequency observations (L3, P3) | | |--------------------------------------------------------| | | 2nd order effect: not applied | | |--------------------------------------------------------| | | other effects: not applied | |---------------------------------------------------------------------------| |*Tidal | solid earth tide: using routine dehanttideinel.f | | | (based on IERS 2003, Ch. 7.1.2) | | |--------------------------------------------------------| | | permanent tidal term: applied in tide model, | | | NOT included in site coordinates | | |--------------------------------------------------------| | | solid Earth pole tide: IERS 2003, Ch. 7, Eq. 23a & 23b | | |--------------------------------------------------------| | | oceanic pole tide: not applied | | |--------------------------------------------------------| | | ocean tide loading: consistent with IERS 2003 (Ch. 7), | | | FES2004 model provided by the Bos & Scherneck | | | website (http://www.oso.chalmers.se/~loading/); | | | site displacement computed using hardisp.f from | | | D. Agnew | | | (http://tai.bipm.org/iers/convupdt/convupdt_c7.html) | | |--------------------------------------------------------| | | ocean tide geocenter: coefficients corrected for center| | | of mass motion of whole Earth | | |--------------------------------------------------------| | | atmosphere tides: not applied | |---------------------------------------------------------------------------| | Non-tidal | atmospheric pressure: not applied | | loadings |--------------------------------------------------------| | | ocean bottom pressure: not applied | | |--------------------------------------------------------| | | surface hydrology: not applied | | |--------------------------------------------------------| | | other effects: not applied | |---------------------------------------------------------------------------| |*Earth orientation| ocean tidal: diurnal/semidiurnal variations in x,y & | | variations | UT1 applied according to IERS 2003 | | |--------------------------------------------------------| | | atmosphere tidal: not applied | | |--------------------------------------------------------| | | high-frequency nutation: subdiurnal nutation terms | | | with periods less than two days (IERS 2003, Tab 5.1) | | | using IERS routine PMsdnut.f | ============================================================================= ============================================================================= | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Time argument | GPS time as given by observation epochs | |---------------------------------------------------------------------------| | Inertial | geocentric; mean equator and equinox of 2000 Jan 1.5 | | | (J2000.0) | |---------------------------------------------------------------------------| | Terrestrial | Initial station coordinates are from ITRF2005, if | | | available, for the rest stations are GFZ estimated. | | | Initial station velocities are from ITRF2005, if | | | available, for the rest stations are computed using | | | NNR-NUVEL1A model (IERS 2003, Ch. 4.2.3) |---------------------------------------------------------------------------| | Tracking | Tracking network is global: up to 403 stations, among | | network | which 187 are CGPS@TG (TIGA) and 216 are IGS stations. | | | Stations are split into 2 subnetworks with up to | | | 217 globally distributed stations each. Subnetworks | | | are combined to form daily solutions using up to 30 | | | globally distributed IGS05 RF stations in the ITRF2005 | | | datum. Daily solutions are combined into three day | | | solutions by applying orbit continuity constraint | | | (Beutler et al. 1996). The weekly SINEX solution is | | | generated by combining 3-day solutions. | |---------------------------------------------------------------------------| | Interconnection | precession: IAU 2000A Precession-Nutation Model | | |--------------------------------------------------------| | | nutation: IAU 2000A Precession-Nutation Model | | |--------------------------------------------------------| | | a priori EOPs: solved polar motion x,y and LOD | ============================================================================= ============================================================================= | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | EIGEN-GL04S1 degree and order 12 and temporal | | (static) | variations of C20, C30 and C40 | | | (C21, S21 modeled acc. to polar motion ) | |---------------------------------------------------------------------------| | | GM = 398600.4415 km**3/sec**2 (IERS 2003, Ch. 6, | | | p. 57, based on the EGM96 model for Terrestrial Time) | | |--------------------------------------------------------| | | AE = 6378.137 1/f = 298.257 | |---------------------------------------------------------------------------| |*Tidal variations | solid earth tides: IERS 2003, Chapter 6.1 | | in geopotential |--------------------------------------------------------| | | ocean tides: IERS 2003, Chapter 6.4 | | |--------------------------------------------------------| | | solid Earth pole tide: IERS 2003, Chapter 6.2 | | |--------------------------------------------------------| | | oceanic pole tide: not applied | |---------------------------------------------------------------------------| | Third-body | Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, | | | Uranus, Neptune, Pluto (regarded as point masses) | | |--------------------------------------------------------| | | Ephemeris: JPL Planetary Ephemeris DE405 | | |--------------------------------------------------------| | | GM_Sun = 132712442076.0 km**3/sec**2 | | | (IERS 2003, Table 1.1) | | | | | | According to IERS Convention 2003, Table 3.1, based on | | | JPL Planetary Ephemeris DE405: | | | | | | Sun-Earth mass ratio = 332946.045 | | | Sun-Mercury mass ratio = 6023600.0 | | | Sun-Venus mass ratio = 408523.71 | | | Sun-Mars mass ratio = 3098708.0 | | | Sun-Jupiter mass ratio = 1047.3486 | | | Sun-Saturn mass ratio = 3497.898 | | | Sun-Uranus mass ratio = 22902.98 | | | Sun-Neptune mass ratio = 19412.24 | | | Sun-Pluto mass ratio = 135200000.0 | | | Earth-Moon mass ratio = 81.30056 (IERS 2003, Table 3.2)| |---------------------------------------------------------------------------| | Solar radiation | a priori: GPSM_XYZ.1 model, Bar-Sever, March 1998 | | pressure model | | | |--------------------------------------------------------| | | Earth shadow model: penumbra | | |--------------------------------------------------------| | | Earth albedo: not applied | | |--------------------------------------------------------| | | Moon shadow: model based on Huang (1985) | | |--------------------------------------------------------| | | satellite attitude: model of Bar-Sever (1996) applied | | | based on nominal yaw rates | |---------------------------------------------------------------------------| |*Relativistic | dynamical correction: Schwarzschild and Lense-Thirring | | effects | solution | | |--------------------------------------------------------| | | gravitational time delay: IERS 2003, Ch. 11, Eq. 17 | |---------------------------------------------------------------------------| | Numerical | method: single step integrator from Everhart | | integration | integration with direct integration of second-order | | of orbit | equations | | |--------------------------------------------------------| | | integration step: variable, automatically controlled | | |--------------------------------------------------------| | | starter procedure: none | | |--------------------------------------------------------| | | arc length: 24 h | |---------------------------------------------------------------------------| | Numerical | method: multistep step integrator Stoermer-Cowell | | integration | with direct integration of second-order equations | | of variation |--------------------------------------------------------| | equations | integration step: fixed | | |--------------------------------------------------------| | | starter procedure: Cowell-Kulikov | | |--------------------------------------------------------| | | arc length: 24 h | ============================================================================= ============================================================================= | ESTIMATED PARAMETERS (APRIORI VALUES AND CONSTRAINTS) | |---------------------------------------------------------------------------| | Adjustment | least-square adjustment according to Ge et al. (2006) | |---------------------------------------------------------------------------| |*Station | Free network strategy (constraints to a priori values | | coordinates | are between 1 m. and 1000 m., no station is fixed). | | | X,Y,Z station coordinates of all stations are adjusted,| | | relative to a priori values from ITRF2005 | |---------------------------------------------------------------------------| | Satellite clock | solved for at each epoch (white noise process) | | | | |---------------------------------------------------------------------------| | Receiver clock | solved for at each epoch (white noise process); | | | one clock fixed and used as a time reference | |---------------------------------------------------------------------------| | Orbits | initial position and velocity, solar radiation pressure| | | scale, y-bias, sine/cosine terms and stochastic | | | impulses (at noon) are estimated for all satellites | |---------------------------------------------------------------------------| | Satellite | yaw rate is estimated for BLOCK II/IIA satellites | | attitude | after shadow crossing | |---------------------------------------------------------------------------| | Troposphere | zenith delay: zenith delay parameters for each station | | | with 1 hour intervals | | |--------------------------------------------------------| | | mapping function: wet Global Mapping Functions (GMF) | | | (Boehm et al., 2006) | | |--------------------------------------------------------| | | zenith delay epochs: each integer hour | | |--------------------------------------------------------| | | gradients: north and east horizontal delay are | | | estimated for each station in daily intervals | |---------------------------------------------------------------------------| | Ionospheric | not estimated | | corrections | | |---------------------------------------------------------------------------| | Ambiguities | ambiguities are fixed according to Ge et al.(2005) | |---------------------------------------------------------------------------| |*Earth orientation| daily x & y pole and pole rate and daily LOD, by weekly| | parameters (EOP) | solution UT1 fixed for 1st day and estimated for the | | | remaining days | |---------------------------------------------------------------------------| | Other parameters | GPS satellite phase center offsets estimated daily | ============================================================================= ============================================================================= | REFERENCES | |---------------------------------------------------------------------------| | Bar-Sever, Y. E. (1996), "A new model for GPS yaw attitude", Journal of | | Geodesy, 70:714-723 | | | | Beutler, G., E. Brockmann, U. Hugentobler, L. Mervart, M. Rothacher, | | R. Weber, "Combining n Consecutive One-Day-Arcs into n-Days-Arc, | | Journal of Geodesy, Vol. 70, pp. 287-299, 1996 | | | | Boehm, J., A.E. Niell, P. Tregoning, H. Schuh (2006), "Global Mapping | | Functions (GMF): A new empirical mapping function based on numerical | | weather model data", Geophysical Research Letters, Vol. 33, L07304, | | DOI:10.1029/2005GL025545. | | | | Boehm, J., R. Heinkelmann and H. Schuh (2007), "Short Note: A global | | model of pressure and temperature for geodetic applications", Journal | | of Geodesy, DOI: 10.1007/s00190-007-0135-3 | | | | Blewitt, G., (1990), An automatic editing algorithm for GPS data. | | Geophysical Research Letters, Vol. 17, No. 3, p. 199-202 | | | | Ge, M., G. Gendt, G.Dick and F.P. Zhang (2005), "Improving carrier-phase | | ambiguity resolution in global GPS", Journal of Geodesy, Volume 80, | | Number 4, July 2006, DOI: 10.1007/s00190-005-0447-0 | | | | Ge, M., G. Gendt, G.Dick, F.P. Zhang and M. Rothacher (2006), "A new data | | processing strategy for huge GNSS global networks", Journal of Geodesy, | | Volume 79, number 1-3, June 2005, DOI: 10.1007/s00190-006-0044-x | | | | Huang, C. (1985), "Estimating Earth Orientation Parameters using SLR data | | of LAGEOS satellite - study on effect of force models", Dissertation, | | Shanghai Astronomical Observatory, Chinese Academy of Sciences | | | | IERS Conventions (2003), McCarthy, D. and Petit, G. (IERS Technical Note | | 32), Frankfurt am Main: Verlag des Bundesamts fuer Karthographie und | | Geodaesie, 2004, 127 pp. | | | | Wu J.,T., S.C. Wu, G.A. Hajj, W.I. Bertiger, and S.M. Lichten (1993). | | "Effects of Antenna Orientation on GPS Phase", Manuscripta Geodetica, | | 18, pp. 91-98. | | | | Zhang F.P., G. Gendt, M. Ge (2007), "GPS Data Processing at GFZ for | | Monitoring the Vertical Motion of Global Tide Gauge Benchmarks", | | Scientific Technical Report STR07/02, GFZ, Potsdam | | | ============================================================================= |* = strong consistency with IERS/IGS conventions is especially important | | for these items | =============================================================================