============================================================================= | IGS ANALYSIS STRATEGY SUMMARY | ============================================================================= | Analysis Center | [center name] | | | [ACN = Analysis Center code] | | | [address] | | | [group phone number] | | | [group fax number] | |---------------------------------------------------------------------------| | Contact people | [name 1] [e-mail 1] [phone 1] | | | [name 2] [e-mail 2] [phone 2] | | | [name 3] [e-mail 3] [phone 3] | |---------------------------------------------------------------------------| | Software used | [name/version], [developer], [YYYY-MM-DD implemented] | |---------------------------------------------------------------------------| | IGS products | ACNwwwwn.sp3 daily orbit files | | generated for | ACNwwww7.erp weekly ERP file of daily values | | GPS Week 'wwww' | ACNwwwwn.clk daily station & SV clock files | | day of Week 'n' | ACNwwww7.sum weekly summary file | | (n=0,1,...,6) | ACNwwww7.snx weekly SINEX file | | | ACNwwwwn.tro daily tropo files (???) | | | ACNGDDD0.YYI daily ionosphere maps (???) | | | | | | [ACN = Analysis Center code] | | | [wwww = GPS week number] | | | [n = GPS day of week number] | | | [DDD = day of year] | | | [YY = year of century] | |---------------------------------------------------------------------------| | Preparation date | YYYY-MM-DD | |---------------------------------------------------------------------------| | Modification dates| YYYY-MM-DD: ... [summary of changes] | | | YYYY-MM-DD: ... [summary of changes] | |---------------------------------------------------------------------------| | Effective date | YYYY-MM-DD | | for data analysis | | ============================================================================= ============================================================================= | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Preprocessing | RINEX files pre-screened using TEQC metrics to reject | | | small/incomplete files (<85%), excessive phase slips | | | (>500), or high multipath (>1.2 m); | | | outliers edited & cycle slips detected/fixed; | | | 1 ms RINEX clock jumps fixed using clockprep; | | | code biases corrected to P1/P2 using cc2noncc; | | | ... [summarize any other preprocessing steps] | |---------------------------------------------------------------------------| | Basic observable | undifferenced carrier phases & pseudoranges | | | [or carrier phase only for double-differencing] | | |--------------------------------------------------------| | | elevation angle cutoff: 10 degrees | | | sampling rate: 5 minute (decimated) | | | weighting: (for raw obs *before* iono correction) | | | carrier phase= 1 cm sigma (nominally) | | | pseudorange= 1 m sigma (nominally) | | | sigmas increase with decreasing elevation | | | angle by factor (1/sin(elev)) | | | deweighting: ... [summarize algorithm, if any] | | | smoothing: ... [summarize procedure, if any] | | | code biases: C1 & P2' corrected to P1 & P2 using | | | cc2noncc tool depending on receiver type | |---------------------------------------------------------------------------| | Modeled | undifferenced, corrected for 1st order ionosphere | | observable | effect to LC & PC | |---------------------------------------------------------------------------| |*Satellite center | SV-specific z-offsets & block-specific x- & y-offsets | | of mass | (from manufacturer) from file igs_05.atx based on | | offsets | GFZ/TUM analyses using fixed ITRF2000 coordinates | | | [refer to IGS Mail #5189, 17 Aug 2005] | |---------------------------------------------------------------------------| |*Satellite phase | block-specific nadir-dependent "absolute" PCVs applied | | center | from file igs_05.atx; no azimuth-dependent corrections | | corrections | applied | | | [refer to IGS Mail #5189, 17 Aug 2005] | |---------------------------------------------------------------------------| |*Satellite clock | 2nd order relativistic correction for non-zero | | corrections | orbit ellipticity (-2*R*V/c) applied | | | [NOTE: other relativistic effects under Orbit Models] | |---------------------------------------------------------------------------| | GPS attitude | GPS satellite yaw attitude model: applied (Bar-Sever, | | model | 1995); yaw rates adjusted as described below | |---------------------------------------------------------------------------| |*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_05.atx | | corrections | [refer to IGS Mail #5189, 17 Aug 2005] | |---------------------------------------------------------------------------| |*Antenna radome | calibration applied if given in file igs_05.atx; | | calibration | otherwise radome effect neglected | |---------------------------------------------------------------------------| |*Marker -> antenna| dN,dE,dU eccentricities from site logs applied to | | ARP eccentricity | compute station coordinates | |---------------------------------------------------------------------------| | Troposphere | met data input: latitude, height, DOY climate model | | a priori model | from T. Herring (private comm.) | | |--------------------------------------------------------| | (parameter | zenith delay: Saastamoinen (1972) "dry" + "wet" | | estimation is |--------------------------------------------------------| | below) | mapping function: NMF for dry & wet parts (Niell, 1995)| |---------------------------------------------------------------------------| |*Ionosphere | 1st order effect: accounted for by dual-frequency | | | observations in linear combination | | |--------------------------------------------------------| | | 2nd order effect: no corrections applied | | |--------------------------------------------------------| | | other effects: no corrections applied | |---------------------------------------------------------------------------| |*Tidal |*solid Earth tide: IERS 2003 (dehanttideinel.f routine) | | displacements |--------------------------------------------------------| | |*permanent tide: zero-frequency contribution left in | | (IERS Conventions| tide model, NOT in site coordinates | | 2003, Ch. 4, eqn |--------------------------------------------------------| | 11) |*solid Earth pole tide: IERS 2003; mean pole removed | | | by linear trend (Ch. 7, eqn 23a & 23b) | | |--------------------------------------------------------| | | oceanic pole tide: not applied (no model available) | | | [IERS model under development] | | |--------------------------------------------------------| | |*ocean tide loading: consistent with IERS 2003 (Ch. 7), | | | site-dependent amps & phases from Bos | | | & Scherneck website for GOT00.2 tide | | | model; NEU site displacements computed | | | using hardisp.f from D. Agnew | | | [IERS model is not well specified] | | |--------------------------------------------------------| | |*ocean tide geocenter: coeffs corrected for center of | | | mass motion of whole Earth | | | [IERS Conventions are ambiguous] | | | [NOTE: geocenter motion should also be included in | | | translational of orbits from inertial to terrestrial | | | frame, but no model is available currently] | | |--------------------------------------------------------| | | atmosphere tides: corrections for S1 & S2 tidal | | | pressure loading not applied (no model | | | available) | | | [IERS model under development] | |---------------------------------------------------------------------------| | 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 (ortho_eop.f)| | |--------------------------------------------------------| | (near 12 & 24 hr | atmosphere tidal: S1, S2, S3 tides not applied | | only; longer | [no IERS model specified yet] | | period tidal |--------------------------------------------------------| | corrections | high-frequency nutation: prograde diurnal polar motion | | should not be | corrections (IERS 2003, Table 5.1) applied | | applied) | using IERS routine PMsdnut.for | | |--------------------------------------------------------| | [NOTE: effects should be 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 | | | (J2000.0) | |---------------------------------------------------------------------------| | Terrestrial | ITRF2000 reference frame realized through the set of up| | | to 99 stations coordinates and velocities given in the | | | IGS internal realization IGS03P33_RS106.snx | |---------------------------------------------------------------------------| | Tracking | use all available stations of the 99 IGb00 set, plus | | network | add others based mostly on geometry up to a total of | | | 150 stations; data are processed in double-difference | | | subnets and combined at the normal equation level; | | | a core net ensures interconnection of the subnets | |---------------------------------------------------------------------------| | Interconnection | precession: IAU 1976 Precession Theory | | |--------------------------------------------------------| | (EOP parameter | nutation: IAU 1980 Nutation Theory, with daily offset | | estimation is | corrections applied from IERS Bulletin A | | below) | | | | [NOTE: errors in 1980 model are sufficiently | | | large that observational corrections should | | | be applied; even with more recent nutation | | | models observational corrections are still | | | needed to account for time-varying FCN | | | effects, which are not predictable] | | |--------------------------------------------------------| | | a priori EOPs: polar motion & UT1 interpolated from | | | IERS Bulletin A, updated weekly, with the | | | restoration of subdaily EOP variations using | | | IERS models (see MODELS above) | ============================================================================= ============================================================================= | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | JGM-3 to degree & order 12; C21 & S21 modeled according| | (static) | to polar motion variations (IERS 2003, Ch. 6) | | |--------------------------------------------------------| | | GM=398600.4415 km**3/sec**2 (for TT/TDT time argument) | | |--------------------------------------------------------| | | AE = 6378136.6 m | |---------------------------------------------------------------------------| | Tidal variations |*solid Earth tides: procedure given in IERS Conventions | | in geopotential | 2003, Chapter 6.1, including anelastic effects and | | | step 2 frequency-dependent corrections to Love | | | number k(2,1) | | |--------------------------------------------------------| | | ocean tides: procedure given in IERS Conventions 2003, | | | Chapter 6.4 applied | | |--------------------------------------------------------| | |*solid Earth pole tide: IERS 2003, Chapter 6.2 | | |--------------------------------------------------------| | | oceanic pole tide: new model of S. Desai applied for | | | C21 and S21 terms only | | | [see IERS Conventions updates] | |---------------------------------------------------------------------------| | Third-body | Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn | | forces | (regarded as point masses) | | |--------------------------------------------------------| | | ephemeris: JPL DE405 | | |--------------------------------------------------------| | | GM_Sun 132712442076.0000 km**3/sec**2 | | | Moon-Earth mass ratio 0.0123000383 | | | Sun-Mercury mass ratio 6023600. | | | Sun-Venus mass ratio 408523.71 | | | Sun-Mars mass ratio 3098708. | | | Sun-Jupiter mass ratio 1047.3486 | | | Sun-Saturn mass ratio 3497.898 | |---------------------------------------------------------------------------| | Solar radiation | a priori: GSPM_EPS model of Bar-Sever (private comm.) | | pressure model | parameterized for variations in direct & | | | orthogonal forces | | (parameter |--------------------------------------------------------| | estimation is | Earth shadow model: umbra & penumbra included | | below) |--------------------------------------------------------| | | Earth albedo: not applied | | |--------------------------------------------------------| | | Moon shadow: not applied | | |--------------------------------------------------------| | | satellite attitude: model of Bar-Sever (1995) applied; | | | yaw rates estimated as described below | |---------------------------------------------------------------------------| |*Relativitic | dynamical correction: IERS 2003, Ch. 10, eqn 1 | | effects | (except Lense-Thirring & geodesic precession | | | terms neglected) | | |--------------------------------------------------------| | | gravitational time delay: IERS 2003, Ch. 11, eqn 17 | |---------------------------------------------------------------------------| | Numerical | variable (high) order Adams predictor-corrector | | integration | with direct integration of second-order equations | | |--------------------------------------------------------| | | integration step: variable | | |--------------------------------------------------------| | | starter procedure: RKF | | |--------------------------------------------------------| | | arc length: 3+24 hours | ============================================================================= ============================================================================= | ESTIMATED PARAMETERS (& APRIORI VALUES & CONSTRAINTS) | |---------------------------------------------------------------------------| | Adjustment | weighted least squares implemented as a Kalman filter | | method | | | | [or weighted least squares and Helmert blocking used | | | to process subnetworks separately and then combine] | |---------------------------------------------------------------------------| | Station | all station coordinates are adjusted, relative to the | | coordinates | a priori values from IGS03P33_RS106.snx; a no-net- | | | rotation condition is applied wrt the IGb00 frame | | | using up to 99 reference frame stations; | | | apriori sigmas are 1 m for each component | |---------------------------------------------------------------------------| | Satellite clock | solved for at each epoch as white noise process with a | | | a steady state sigma of 1 sec | |---------------------------------------------------------------------------| | Receiver clock | solved for at each epoch as white noise process with a | | | a steady state sigma of 1 sec; one station clock fixed | | | & used as a timescale reference, usually USNO | |---------------------------------------------------------------------------| | Orbits | deterministic positions and velocities, y-bias, solar | | | radiation pressure scale in direct direction; | | | stochastic accelerations in SV x,y,z directions with | | | steady state sigma of 0.125e-12 km/s/s and correlation | | | time of 4 hrs solved for every 30 min, nominally; | | | stochastic sigma increased for SV with poor fits based | | | on prior preliminary solution or prior history; | | | apriori values are based on solution for previous day | |---------------------------------------------------------------------------| | Satellite | deterministic yaw bias with yaw rates estimated as | | attitude | white noise for satellites which are eclipsing with | | | a steady state sigma of 0.01 deg/sec, solved for every | | | 6 hours | |---------------------------------------------------------------------------| | Troposphere | zenith delay: estimated for each observation as a | | | random walk with process noise of | | | 1.0 cm/sqrt(hr) | | | [or if segmented model used give model | | | form and segment interval] | | |--------------------------------------------------------| | | mapping function: partial is NMF wet (Niell, 1995) | | |--------------------------------------------------------| | | zenith delay epochs: reported for each observation | | | epoch | | | [if segmented model used, give epochs of | | | tabulated values] | | |--------------------------------------------------------| | | gradients: 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 | | correction | | |---------------------------------------------------------------------------| | Ambiguity | phase cycle ambiguities adjusted except when they can | | | be resolved confidently (<2 cm uncertainty), in which | | | case they are fixed | |---------------------------------------------------------------------------| |*Earth orientation| daily x & y pole offsets, pole-rates, and LOD at noon | | parameters (EOP) | epochs; rates constrained to 32.2 mas/day; | | | UT1 not estimated | |---------------------------------------------------------------------------| | Other | ... [explain] | | parameters | | ============================================================================= ============================================================================= | REFERENCES | |---------------------------------------------------------------------------| | | | Bar-Sever, New GPS attitude model, IGS Mail #591, 1995, | | http://igscb.jpl.nasa.gov/mail/igsmail/1994/msg00166.html | | | | Bos, M.S., & H.-G. Scherneck, website at www.oso.chalmers.se/~loading/ | | | | IERS Conventions 2003, D.D. McCarthy & G. Petit (editors), IERS Technical | | Note 32, Frankfurt am Main: Verlag des Bundesamts fuer Kartographie und | | Geodaesie, 2004. | | | | Niell, A.E., Global mapping functions for the atmosphere delay at radio | | wavelengths, J. Geophys. Res., 101(B2), 3227-3246, 1993. | | | | 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, and S.M. Lichten, Effects of | | antenna orientation on GPS carrier phase, Manuscripta Geodaetica,18, | | 91-98, 1993. | | | ============================================================================= |* = strong consistency with IERS/IGS conventions is especially important | | for these items | =============================================================================