============================================================================= INTERNATIONAL GPS SERVICE GOP Analysis Strategy Summary ============================================================================= Analysis centre | Geodetic Observatory Pecny | Research Institute of Geodesy, Topography and Cartography | Ondrejov 244 | CZ 251 65 | Czech Republic | Phone: +420 323 649 235 | Fax: +420 323 649 236 | Data archive: ftp://ftp.pecny.cz/LDC | WWW homepage: http://www.pecny.cz/gop | | Cooperation of: | RIGTC-GOP and the Czech Technical University in Prague ----------------------------------------------------------------------------- Contact Person(s) | Jan Dousa | E-mail: dousa@fsv.cvut.cz | Phone: +420 323 649 235 (Geodetic Observatory Pecny) | Leos Mervart | E-mail: mervart@fsv.cvut.cz | Phone: +420 224 354 805 (Czech Technical University) ----------------------------------------------------------------------------- Software Used | Bernese GPS Software V5.0(+modif), developed at AIUB ----------------------------------------------------------------------------- Ultra-Rapid | GOUwwwwd_hh.sp3 GPS ephemeris & clock files for 24 hours product generated | fitted and 24 hours predicted GPS every 3 hours | satellite positions tabulated at 15 min | intervals. (Clocks are not estimated!) (gps week='wwww' | GOUwwwwd_hh.erp ERP (X,Y pole, UT1-UTC estimates) files day of week='d' | for 24 hours fitted and 24 hours hour='hh') | predicted information reported in | the middle epoch of respected 24h span. ----------------------------------------------------------------------------- Preparation Date | 30-Jan-2004 ----------------------------------------------------------------------------- Modification Dates| 05-Dec-2007 ----------------------------------------------------------------------------- Effective Date for| 13-Sep-2006 Data Analysis | ============================================================================= ----------------------------------------------------------------------------- | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Preprocessing | Hourly RINEX files concatenated by TEQC to 6h batches | | | and screened for small incomplete data, high multipath | | | or large number of cycle-slips. | | | Code biases corrected to P1/P2 using cc2noncc. | | | Cycle slip detection based on triple-difference sol. | | | Cycle slips mostly fixed or a new ambiguity is set up | | | if not for too small data pieces, which are removed. | | | Data are also screened using weighted postfit residuals| | | from ionosphere-free linear combination and outliers | | | are removed. | | | Preprocessing is done only for 6-hour data batches | | | in two iterative steps after improving the orbits. | |---------------------------------------------------------------------------| | Basic observable | Carrier phase and code. | | | Code is used only for receiver clock synchronization, | | | ionosphere estimates and widelane ambiguity resolution.| | |--------------------------------------------------------| | | Elevation angle cut-off : 7 degrees | | | Elevation dep. weighting: 1/cos(zenith)**2 | | | Sampling rate : 30sec/5min(final estimation) | |---------------------------------------------------------------------------| | Modeled observ. | Double differences, ionosphere-free linear combination.| |---------------------------------------------------------------------------| | Satellite antenna| SV-specific Z-offsets & block-specific x- & y-offsets | | center of mass | from file in igs05_1365.atx based on GFZ/TUM analyses | | offsets | using fixed ITRF2000 coordinates. | | | [refer to IGS Mail #5189, 17 Aug, 2005] | |---------------------------------------------------------------------------| | Satellite antenna| Block-specific nadir-angle dependent "absolute" PCVs | | phase center | applied from file igs05_1365.atx; no azimuth-dependent | | corrections | corrections applied. | | | [refer to IGS Mail #5189, 17 Aug, 2005] | |---------------------------------------------------------------------------| | Satellite clock | Periodic, -2(R*V/c): applied | | corrections | | |---------------------------------------------------------------------------| | Gps attitude | Not applied | | model | | |---------------------------------------------------------------------------| | RHC phase | Phase polarization effects applied (Wu et al., 1993) | | rotation corr. | | |---------------------------------------------------------------------------| | Ground antenna | "Absolute" elevation- & azimuth-dependent PCVs (when | | phase center | available) and L1/L2 offsets from ARP applied from the | | offsets and | latest igs05_.atx file. | | corrections | [refer to IGS Mail #5189, 17 Aug, 2005] | |---------------------------------------------------------------------------| | Antenna radome | Calibrations applied if given in igs05_.atx file,| | callibration | otherwise radome effect neglected (radome: NONE) | |---------------------------------------------------------------------------| | Marker -> ARP | dN,dE,dU eccentricities from site logs applied to | | eccentricity | compute stations coordinates. | |---------------------------------------------------------------------------| | Troposphere | A priori model : Hydrostatic component | | | (Saastamoinen, 1973). | | |--------------------------------------------------------| | | Met data input : none | | |--------------------------------------------------------| | | Mapping function: Dry Niell mapping functions | | | (Niell, 1996) | | |--------------------------------------------------------| | | Gradient model : not applied | |---------------------------------------------------------------------------| | Ionosphere | 1st order ionosphere effect eliminated by forming the | | | ionosphere-free linear combination of L1 and L2. | | | 2nd and the higher ionosphere effects not corrected. | |---------------------------------------------------------------------------| | Tidal | Solid Earth tide: IERS 2003 (since Jun 15,2006) | | displacements | IERS 1996 before (McCarthy, 1996) | | |--------------------------------------------------------| | | Permanent tides: zero-frequency applied in tide model | | | not in site coordinates | | |--------------------------------------------------------| | | Solid Earth pole tide: IERS 1996 with constant pole | | | offsets: xp=0.033, yp=0.331 as. | | |--------------------------------------------------------| | | Ocean tide loading: IERS 2003, site-dependent ampl&pha | | | (Bos & Scherneck) | | | FES2004 model (since Jun 15, 2006) | | | NEU site displacements computed | | | computed using hardisp.f(D. Agnew) | | |--------------------------------------------------------| | | Ocean tide geocenter: coefficients corrected for center| | | of mass motion of the whole Earth| | | CMC correct. applied to SP3orbits| | |--------------------------------------------------------| | | Atmosphere tides: not applied | |---------------------------------------------------------------------------| | Non-tidal loading| Atmospheric preassure: not applied | | |--------------------------------------------------------| | | Ocean bottom preassure: not applied | | |--------------------------------------------------------| | | Surface hydrology: not applied | | |--------------------------------------------------------| | | Other effects: not applied | |---------------------------------------------------------------------------| | Earth orientation| Ocean tidal: IERS 2003 | | models (EOP) |--------------------------------------------------------| | | Atmosphere tidal: not applied | | |--------------------------------------------------------| | | High-frequency nutation: not applied | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | REFERENCE FRAMES | ----------------------------------------------------------------------------- | Time argument | TDT | |---------------------------------------------------------------------------| | Inertial frame | Geocentric; mean equator and equinox of 2000 Jan 1 | | | at 12:00 (J2000.0) | |---------------------------------------------------------------------------| | Terrestrial | IGS05 reference frame realized from the subset of | | frame | station coordinates and velocities given in the IGS | | | internal realization aligned to ITRF2005.The stations | | | are selected from the consistency check applying the | | | NNR+NNT constraints w.r.t. IGS05 coordinates (2/2/4cm).| | | Only stations uploading hourly RINEX files are applied.| |---------------------------------------------------------------------------| | Tracking network | Use of IGS stations globally distributed selected with | | | respect to more further criterions: | | | 1. hourly & RT data (with long-term low latency) | | | 2. reference frame | | | 3. all data collection (including unhealthy satellites)| | | 4. long-term quality indicator from teqc | |---------------------------------------------------------------------------| | Interconnection | Precession: IAU 1976 | | |--------------------------------------------------------| | | Nutation: IAU 2000 | | |--------------------------------------------------------| | | A priori EOPs: IERS Rapid Service/Prediction Center | ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | JGM3 model up to degree and order 12 (+C21+S21) | | |--------------------------------------------------------| | | GM = 398600.4415 km**3/sec**2 | | |--------------------------------------------------------| | | AE = 6378.1363 km | |---------------------------------------------------------------------------| | Third-body | Sun and Moon as point masses | | |--------------------------------------------------------| | | Ephemeris: JPL DE200 | | |--------------------------------------------------------| | | GMsun = 132712500000 km**3/sec**2 | | |--------------------------------------------------------| | | GMmoon = 4902.7890 km**3/sec**2 | |---------------------------------------------------------------------------| | Tidal forces | Solid Earth tides: frequency independent Love's | | | number K2= 0.300 | | |--------------------------------------------------------| | | Solid Earth pole tides: | | |--------------------------------------------------------| | | Ocean tides: UT CSR model (IERS 1996) | | |--------------------------------------------------------| | | Oceanic pole tides: not applied | |---------------------------------------------------------------------------| | Solar radiation | Direct radiation: CODE model 98-01 (Springer, 1998) | | pressure |--------------------------------------------------------| | | Estimated RPR parameters (Beutler 1994): | | | constants in D-, Y- and X-direction | | | amd eriodic terms in X-direction | | |--------------------------------------------------------| | | Earth shadow model: cylindric shadow | | |--------------------------------------------------------| | | Moon shadow model: umbra and penumbra | | |--------------------------------------------------------| | | Earth albedo: not applied | | |--------------------------------------------------------| | | Reflection radiation: not applied | | |--------------------------------------------------------| | | Satellite attitude model: not applied | |---------------------------------------------------------------------------| | Numerical | Integration algorithms developed at AIUB (Beutler 1990)| | Integration | Representation of the orbit by a polynomial of degree | | | 10 for 1 hour | | |--------------------------------------------------------| | | Integration step: 1 hour | | |--------------------------------------------------------| | | Starter procedure: no special starter procedure needed | | |--------------------------------------------------------| | | Arc length : 24-72 hours (in most cases 72 hours) | ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | ESTIMATED PARAMETERS (APRIORI VALUES & SIGMAS) | |---------------------------------------------------------------------------| | Adjustment | Weighted least-squares algorithm. Helmert blocking | | | applied to combined subnetworks and 6h-solutions. | |---------------------------------------------------------------------------| | Station | All coordinates estimated in the IGS05 realization of | | coordinates | the ITRF2005. The datum is realized through the set of | | | stations selected by checking the consistency of the | | | NNR+NNT constrained solution w.r.t. IGS05 coordinates. | | | The coordinates of the selected stations are tightly | | | constrained (1mm) to their a priori IGS05 values. | |---------------------------------------------------------------------------| | Data span | 6-hour batches for the preprocessing steps and normal | | | equation saving. Final orbit arc and EOPs are estimated| | | from 72 hours using normal equation stacking procedure.| |---------------------------------------------------------------------------| | Satellite clocks | Satellite clocks not estimated, but eliminated by | | | forming double-differences. Broadcast clocks in SP3. | |---------------------------------------------------------------------------| | Receiver clock | Receiver clocks are synchronized during preprocessing | | bias | using the pseudorange measurements. Receiver clocks | | | are not estimated, but eliminated in double-differences| |---------------------------------------------------------------------------| | Orbital | 6 Keplerian elements plus 5 solar radiation parameters | | parameters | (Beutler 1994) at start of arc. | | | A priori orbits are based on merged broadcast and IGS | | | ultra-rapid orbits predictions and two-way iterative | | | procedure is applied for the orbits. | | | Estimated RPR parameters are: constants in D-, Y- and | | | X-direction; periodic in X-direction. Whenever problem | | | in long-arc (3-day) combination, correspoding orbit | | | arc is splitted. | |---------------------------------------------------------------------------| | Troposphere | zenith delay: Continuous piece-wise linear troposphere | | | zenith delay parameters are estimated | | | for each station with intervals of 2 | | | hours. Weak a priori constraints of | | | 5m are applied. | | |--------------------------------------------------------| | | mapping fuction: Wet Niell mapping function | | | (Niell,1996) | | |--------------------------------------------------------| | | gradients: not estimated | |---------------------------------------------------------------------------| | Ionospheric corr.| Not estimated (ionosphere-free based analysis) | |---------------------------------------------------------------------------| | Ambiguity | Resolved in 6-hour batches using wide- & narrow-lane | | | SIGMA strategy. For wide-lane ambiguities, code is used| | | if good quality observations are available. | |---------------------------------------------------------------------------| | Earth Orient. | X- and Y-pole coordinates, and UT1-UTC represented | | Parameters (EOP) | with continuous piece-wise linear function using 24 h | | | time resolution. The UT1-UTC is fixed to the a priori | | | value at the beginning of the first day. | | | No other constraints are applied. | |---------------------------------------------------------------------------| | Other parameters | center of mass coorinates: not estimated | | |--------------------------------------------------------| | | satellite attitude: not estimated | | |--------------------------------------------------------| | | satellite phase center offsets: not estimated | | |--------------------------------------------------------| | | satellite phase center variation: not estimated | |---------------------------------------------------------------------------| REFERENCES: Beutler, G. (1990), Numerische Integration gewoehnlicher Differential- gleichungssysteme: Prinzipien und Algorithmen. Mitteilungen der Satelliten-Beobachtungsstation Zimmerwald, No. 23, Druckerei der Universitaet Bern, 1990. Beutler, G., E. Brockmann, W. Gurtner, U. Hugentobler, L. Mervart, and M. Rothacher (1994), 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, April 1994. Bos, M.S., H.-G. Scherneck, website at www.oso.chalmers.se/~loading/. IERS Conventions 2003 (2004), D.D. McCarthy & G. Petit (eds), IERS Technical Note 32, Frankfurt am Main: Verlag des Bundesamts fuer Kartographie und Geodaesie. Niell, A.E. (1996), Global Mapping Functions for the Atmosphere Delay at Radio Wavelengths, Journal of Geophysical Research, 101(B2), 3227-3246. Saastamoinen, J. (1972), 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. Springer, T.A., G. Beutler, M. Rothacher (1999), A new Solar Radiation Pressure Model for the GPS Satellites, Adv. Space Res., 23, No. 4, pp. 673-679. Wu, J.T., S.C. Wu, G.A. Hajj, W.I. Bertiger, S.M. Lichten (1993), Effects of antenna orientation on GPS carrier phase. Manuscripta Geodaetica 18, 1993, pp. 91-98.