============================================================================= | | | | | INTERNATIONAL GNSS SERVICE | | | | USNO Rapid-Product Analysis Strategy Summary | | | | | ============================================================================= | Analysis Center | U.S. Naval Observatory | | | Earth Orientation Dept. | | | 3450 Massachusetts Avenue, NW | | | Washington, DC 20392-5420 | | | USA | | | Phone: see below | | | Fax: 202-762-1563 | |---------------------------------------------------------------------------| | Contact People | Christine Hackman: hackman.christine@usno.navy.mil | | | Sharyl Byram: sharyl.byram@usno.navy.mil | | | Victor Slabinski: slabinski.victor@usno.navy.mil | | | Jeffrey Tracey: jeffrey.tracey@usno.navy.mil | | | | | | Telephone numbers: | | | | | | Hackman: 202-762-1428 | | | Byram: 202-550-6407 | | | Slabinski: 202-762-0365 | | | Tracey: 202-762-0403 | |---------------------------------------------------------------------------| | Software Used | Bernese GPS Software Version 5 | |---------------------------------------------------------------------------| | IGS Products | Contributions to IGS Rapid combination beginning | | Generated for | 03 April 1997: | | GPS Week 'wwww' | usnwwwwn.sp3 GPS ephemeris/clock files in daily files | | Day of Week 'n' | at 15-min intervals in sp3 format, | | (n=0,1,...,6) | including accuracy codes computed from | | | the formal orbit errors of the solution | | | usnwwwwn.erp EOP (pole, pole rates and LODR estimates;| | | a priori UT1-UTC) in daily files | | | usnwwwwn.clk Satellite and receiver clock estimates | | | at 5-min intervals in RINEX format | |---------------------------------------------------------------------------| | Preparation Date | 15 Mar. 2010 | |---------------------------------------------------------------------------| | Effective Date | 14 Apr. 1999 | | for Data Analysis | | ============================================================================= ============================================================================= | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Preprocessing | Phase preprocessing in a baseline by baseline mode | | | using triple-differences. In most cases, cycle slips | | | are fixed looking simultaneously at different linear | | | combinations of L1 and L2. If a cycle slip cannot be | | | fixed reliably, bad data points are removed or new | | | ambiguities are set up. In addition, a data screening | | | step on the basis of weighted postfit residuals is | | | performed. Outliers are removed. | |---------------------------------------------------------------------------| | Basic Observable | GPS carrier phase and code | | |--------------------------------------------------------| | | Elevation angle cutoff : 3 degrees | | | Sampling rate : 3 minutes | | | Weighting : a priori uncertainty of 1 mm | | | for L1 carrier-phase | | | measurements; | | | elevation-dependent weighting| | | function [1/cos(z)**2] | | | applied | |---------------------------------------------------------------------------| | Modeled | Double differences, ionosphere-free linear combination | | observable | | |---------------------------------------------------------------------------| | RHC phase | Phase polarization effects applied (Wu et al., 1993) | | rotation corr. | | |---------------------------------------------------------------------------| | Ground antenna | IGS05 PCV model applied starting 6 Jan. 2009; IGS01 | | phase center | model applied prior to that. | | calibrations | | |---------------------------------------------------------------------------| | Troposphere | A priori model : Standard values p, T, RH; | | | Saastamoinen zenith delay; dry | | | Niell mapping function; apriori | | | azimuthal gradients set to zero. | | |--------------------------------------------------------| | | Met data input : No met measurements used. | | |--------------------------------------------------------| | | Estimation : Zenith delay corrections are | | | estimated in piecewise-constant | | | 2-hour intervals. | | | N-S and E-W horizontal delay | | | parameters are solved for every | | | 24 hours. | | |--------------------------------------------------------| | | Constraints : Both zenith and gradient parameters | | | are treated as completely | | | unconstrained. | | |--------------------------------------------------------| | | Mapping function: wet Niell | |---------------------------------------------------------------------------| | Ionosphere | Not modeled (first-order effect eliminated by forming | | | the ionosphere-free linear combination of L1 and L2). | |---------------------------------------------------------------------------| | Plate motions | IGS05 station velocities | |---------------------------------------------------------------------------| | Tidal | Solid earth tidal displacement: complete model from | | displacements | IERS Conventions 2003 | | | | | | Permanent tidal term : applied in tide model, | | | NOT included in site | | | coordinates | | |--------------------------------------------------------| | | Pole tide : applied (IERS, 2003) | | |--------------------------------------------------------| | | Ocean tidal loading: FES2004.BLQ | |---------------------------------------------------------------------------| | Atmospheric load.| Not applied | |---------------------------------------------------------------------------| | Earth orientation| Tidal UT1 (> 5 days): modeled | | models (EOP) | Subdaily ERPs : IERS2000 model | | | | | | Nutation + | | | Precession : IAU2000 model | |---------------------------------------------------------------------------| | Satellite center | IGS05 PCV model applied. | | of mass | | | correction | | |---------------------------------------------------------------------------| | Satellite phase | IGS05 PCV model applied. | | center calibrat. | | |---------------------------------------------------------------------------| | GPS Attitude | Not applied. | ============================================================================= ============================================================================= | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | JGM3 model up to degree and order 12 (+C21+S21) | | |--------------------------------------------------------| | | GM = 398600.4415 km**3/sec**2 | | |--------------------------------------------------------| | | AE = 6378.137 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 | |---------------------------------------------------------------------------| | Solar radiation | Direct radiation: CODE RPR model coefficients | | pressure | (updated 2007) | | |--------------------------------------------------------| | | Estimated RPR parameters : | | | Constants in D-, Y- and X-direction | | | Periodic terms in X-direction | | |--------------------------------------------------------| | | Earth shadow model includes: cylindric shadow | | |--------------------------------------------------------| | | Moon shadow model includes: umbra and penumbra | | |--------------------------------------------------------| | | Reflection radiation: not included | | |--------------------------------------------------------| | | New GPS satellite attitude model: not applied | |---------------------------------------------------------------------------| | Tidal forces | Solid earth tides: TIDE2000 (IERS 2000) | | |--------------------------------------------------------| | | Ocean tides: OT CSR30 model, plus TEG-2B | |---------------------------------------------------------------------------| | Relativity | Applied (IERS 2003) | |---------------------------------------------------------------------------| | Numerical | Integration algorithms developed at AIUB by Gerhard | | Integration | Beutler. 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 hours. | ============================================================================= ============================================================================= | ESTIMATED PARAMETERS (APRIORI VALUES & SIGMAS) | |---------------------------------------------------------------------------| | Adjustment | Weighted least-squares algorithms | |---------------------------------------------------------------------------| | Station | Starting with GPS week 1400, the IGS realization of | | coordinates | ITRF2005 (IGS05) is used, but IGS05 PCV values not | | | applied until 6 Jan 2009. Between Nov 2006 and Jan | | | 2009, IGS01 PCV values used instead. | |---------------------------------------------------------------------------| | Satellite and | Zero-difference data analysis for GPS clock estimation:| | receiver clock | | | | Satellite clock corrections are computed | | | on the basis of the double-difference orbit, ERP, | | | coordinate, and troposphere solutions. The generation | | | of clock results is performed via least-squares | | | adjustment with a sampling rate of 5 min | | | using phase and code observations. | |---------------------------------------------------------------------------| | Orbital | 6 Keplerian elements plus constant D- (direct solar | | parameters | radiation pressure) and Y- (y-bias) terms | | | at start of arc; no a priori sigmas used. | | | | | | IGS ultra-rapid orbits are used as a priori solutions. | |---------------------------------------------------------------------------| | Troposphere | Zenith delay parameters and pairs of horizontal delay | | | gradient parameters are estimated for each station in | | | intervals of 2 hours and 24 hours. No a priori | | | constraints are applied. Piece-wise, linear | | | parameterization. | |---------------------------------------------------------------------------| | Ionospheric | Not estimated in ionosphere-free analyses | | correction | | |---------------------------------------------------------------------------| | Ambiguity | Ambiguities are resolved in a baseline-by-baseline | | | mode using the SIGMA approach, first with L5 (widelane)| | | then with L3 (narrowlane). | |---------------------------------------------------------------------------| | Earth Orient. | X- and Y-pole coordinates, and UT1-UTC are represented | | Parameters (EOP) | each with piece-wise linear polynomials which are | | | continuous in time. UT1-UTC is fixed to the a priori | | | value at the beginning of the first day. | ============================================================================= ============================================================================= | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Inertial | Geocentric; mean equator and equinox of 2000 Jan 1 | | | at 12:00 (J2000.0) | |---------------------------------------------------------------------------| | Terrestrial | IGS05 station coordinates and velocities | |---------------------------------------------------------------------------| | Interconnection | Precession: IAU 2000 Precession Theory | | |--------------------------------------------------------| | | Nutation: IAU 2000 Nutation Theory | | |--------------------------------------------------------| | | Tidal variations in UT1: periods > 5.8 days modeled | | | but not removed (UT1-UTC sol.)| =============================================================================