============================================================================= | IGS ANALYSIS STRATEGY SUMMARY | ============================================================================= | Analysis Center | Natural Resources Canada (EMR: Ultra Rapid - EMU) | | | 615 Booth Street | | | Ottawa, Ontario, Canada | | | K1A 0E9 | | | | | | Phone: 613 947 7937 | | | Fax: 613 995 3215 | | | Web: http://www.geod.nrcan.gc.ca | |---------------------------------------------------------------------------| | Contact people | Yves Mireault | | | E-mail: ymireaul@NRCan.gc.ca | | | Phone: 613 947 7937 | |---------------------------------------------------------------------------| | Software Used | For EMR Ultra Rapid products: EMU | | | Bernese GPS Software V5.0 developed at AIUB | | | (+ in-house modifications) | |---------------------------------------------------------------------------| | IGS Ultra Rapid | emuwwwwd_hh.sp3 48-hour GPS ephemeris and clock file | | product generated | from which the first 24 hours are | | every hour. | based on real data and the last | | | 24 hours are predictions. | | gps_week = 'wwww' | Satellite orbits and clocks are | | day_of_week ='d' | tabulated every 15 minutes. | | hour_of_day ='hh' | emuwwwwd_hh.erp 48-hour ERP file (i.e. x/y pole, | | | x/y pole rates, LOD and UT1-UTC) from | | | which the first 24 hours are based | | | on real data and the last 24 hours are| | | predictions. | | | ERP epochs are given at the middle | | | epoch of each 24-hour span. | | | igu_emrwwwwd_hh.sum List of all stations used. | | | emuwwwwd_hh.clk GPS satellite clock corrections | | | for the estimated 24-hour segment in | | | clock RINEX format. | | | Both 5-min and 30-sec clock rates are | | | estimated and made available | | | internally in 2 different files. | | | emuwwwwd_hh.tro Hourly troposphere delay estimates | | | in troposphere SINEX format. | | | Available internally-- Not needed by | | | IGS anymore! | | | | | | Note: Only the files (sp3,erp,sum) ending at hh=00,06,| | | 12,18 are sent to the IGS ACC for the IGU | | | combination which occurs only at the above | | | specific times. | |---------------------------------------------------------------------------| | Preparation date | 2008-08-25 | |---------------------------------------------------------------------------| | Modification dates| YYYY-MM-DD: ... [summary of changes] | |---------------------------------------------------------------------------| | Effective date | 2005-05-16 | | for data analysis | | ============================================================================= ============================================================================= | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Preprocessing | Orbits: | | | Last 3h,4h or 5h hourly RINEX files are gathered. | | | Code biases corrected to P1/P2 using cc2noncc | | | (when needed). | | | Code data screened using zero difference pseudo-ranges.| | | Phase preprocessing in a baseline/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. | | | | | | Clocks: | | | Last 24h hourly RINEX files are gathered. | | | Code biases corrected to P1/P2 using cc2noncc. | | | (when needed). | | | Simultaneous code and phase RINEX observations from | | | both frequencies to each satellite are used to | | | detect/fix cycle slips and remove outliers. | | | Code observations are smoothed using the phase meas. | | | In addition, a data screening step on the basis of | | | weighted postfit residuals is performed. Outliers | | | are removed. | |---------------------------------------------------------------------------| | Basic observable | Carrier phase; code only used for receiver clock | | | synchronization and the Melbourne-Wubbena ambiguity | | | resolution. | |--------------------------------------------------------| | | Elevation angle cutoff: 5 degrees | | | Sampling rate: 30 seconds (preprocessing) | | | 3/5 minutes (orbits/clocks) | | | | | | Weighting: WHTPHA 1.E+0 | | | ------ = ----- | | | WHTCOD 1.E-4 | | | | | | Elevation dep. weighting: 1/cos(zenith)**2 | | | Smoothing: Code obs. smoothed using the phase meas. | | | (for clock estimation). | | | Code biases: Code biases corrected to P1/P2 using | | | cc2noncc (depending on receiver type). | |---------------------------------------------------------------------------| | Modeled | Orbits: Double differences, ionosphere-free linear | | observable | combination. | | | Clocks: Zero differences, ionosphere-free linear | | | combination. | |---------------------------------------------------------------------------| |*Satellite antenna| SV-specific z-offsets & block-specific x- & y-offsets | | -center of mass | (from manufacturers) from latest igs05_wwww.atx file | | offsets | based on GFZ/TUM analyses using fixed ITRF2000 coords | | | [refer to IGS Mail #5189, 17 Aug 2005] | |---------------------------------------------------------------------------| |*Satellite antenna| Block-specific nadir angle-dependent "absolute" PCVs | | phase center | applied from the latest igs05_wwww.atx file; | | corrections | no azimuth-dependent 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. | |---------------------------------------------------------------------------| | GPS attitude | Not applied | | model | | |---------------------------------------------------------------------------| |*RHC phase | Phase polarization effects applied (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 & | the latest igs05_wwww.atx file | | corrections | [refer to IGS Mail #5189, 17 Aug 2005] | |---------------------------------------------------------------------------| |*Antenna radome | Calibrations applied if given in the igs05_wwww.atx | | calibration | file, otherwise radome effect neglected (radome: NONE) | |---------------------------------------------------------------------------| |*Marker -> antenna| dN,dE,dU eccentricities from site logs applied to | | ARP eccentricity | compute station coordinates | |---------------------------------------------------------------------------| | Troposphere | Met data input: Standard atmosphere, Berg (1948) | | a priori model |--------------------------------------------------------| | | Zenith delay: Saastamoinen-based hydrostatic | | | component mapped with the dry-Niell | | | mapping function | | |--------------------------------------------------------| | | Mapping function: Dry Niell mapping functions | | | (Niell, 1996) | | |--------------------------------------------------------| | | Gradient model : Not applied | |---------------------------------------------------------------------------| |*Ionosphere | 1st order effect: Eliminated by forming the | | | ionosphere-free linear combination | | | of L1 and L2. | | |--------------------------------------------------------| | | 2nd order effect: No corrections applied | | |--------------------------------------------------------| | | Other effects: No corrections applied | |---------------------------------------------------------------------------| |*Tidal | Solid Earth tide: IERS 2003 | | displacements |--------------------------------------------------------| | | Permanent tides: applied in tide model, NOT included | | | in site coordinates | | |--------------------------------------------------------| | | Solid Earth pole tide: applied (IERS, 2003). | | | nominal mean m1= 0.033 arcsec | | | m2= 0.331 arcsec | | |--------------------------------------------------------| | | Oceanic pole tide: Not applied | | |--------------------------------------------------------| | | Ocean tide loading: FES2004 | | |--------------------------------------------------------| | | Ocean tide geocenter: coefficients corrected for center| | | of mass motion (CMC) of the whole| | | Earth; CMC corrections also | | | applied to SP3 orbits | | |--------------------------------------------------------| | | Atmosphere tides: corrections for S1 & S2 tidal | | | pressure loading not applied | | | (no model available yet) | | | [IERS model under development] | |---------------------------------------------------------------------------| | Non-tidal | Atmospheric pressure: Not applied | | loadings |--------------------------------------------------------| | | Ocean bottom pressure: Not applied | | |--------------------------------------------------------| | | Surface hydrology: Not applied | | |--------------------------------------------------------| | | Other effects: Not applied | |---------------------------------------------------------------------------| |*Earth orientation| Ocean tidal: IERS 2003 | | variations |--------------------------------------------------------| | | 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. | |---------------------------------------------------------------------------| | Tracking | About 45 hourly stations dynamically selected at the | | network | time of processing. Stations are processed in 1 global | | | network. Stations are chosen according to: | | | - timely hourly data availability (last few hours) | | | - among the 132 IGS05 Reference frame stations | | | - good quality data | |---------------------------------------------------------------------------| | Interconnection |*Precession: IAU 2000 Precession Theory | | |--------------------------------------------------------| | |*Nutation: IAU 2000 Nutation Theory | | |--------------------------------------------------------| | | A priori EOPs: IERS Bulletin A | ============================================================================= ============================================================================= | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | JGM3 model up to degree and order 12 (+C21+S21) | | |--------------------------------------------------------| | | GM = 398600.4415 km**3/sec**2 | | |--------------------------------------------------------| | | AE = 6378.1363 km | |---------------------------------------------------------------------------| |*Tidal variations | Solid Earth tides: frequency independent Love's | | in geopotential | number K2= 0.300 | | |--------------------------------------------------------| | | Ocean tides: UT CSR 3.0 model | | |--------------------------------------------------------| | | Solid Earth pole tide: IERS 2003 | | |--------------------------------------------------------| | | Oceanic pole tide: Not applied | |---------------------------------------------------------------------------| | Third-body | Sun, Moon, Venus, Mars, Jupiter | | forces | (regarded as point masses) | | |--------------------------------------------------------| | | ephemeris: JPL DE400 | | |--------------------------------------------------------| | | GM sun = 132712500000 km**3/sec**2 | | | GM moon = 4902.7890 km**3/sec**2 | | | | | | Moon-Earth mass ratio | | | Sun-Mercury mass ratio | | | Sun-Venus mass ratio | | | Sun-Mars mass ratio | | | Sun-Jupiter mass ratio | | | Sun-Saturn mass ratio | |---------------------------------------------------------------------------| | Solar radiation | A priori: CODE model C980101 (Springer et al., 1999) | | pressure model |--------------------------------------------------------| | | Earth shadow model: cylindric shadow | | |--------------------------------------------------------| | | Earth albedo: Not applied | | |--------------------------------------------------------| | | Moon shadow: Umbra and penumbra | | |--------------------------------------------------------| | | Satellite attitude: Not applied | |---------------------------------------------------------------------------| |*Relativistic | Periodic, -2(R*V/c): applied | | effects |--------------------------------------------------------| | | Dynamical correction: applied (IERS 2003) | | |--------------------------------------------------------| | | Gravitational time delay: IERS 2003, Ch. 11, eqn 17 | |---------------------------------------------------------------------------| | Numerical | Method: Integration algorithms developed at AIUB | | Integration | (Beutler 1990). 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 : 30-72 hours | ============================================================================= ============================================================================= | ESTIMATED PARAMETERS (APRIORI VALUES AND CONSTRAINTS) | |---------------------------------------------------------------------------| | Adjustment | Weighted least-squares algorithm. Helmert blocking | | | applied to combine the 3h-solutions. | |---------------------------------------------------------------------------| | Station | All coordinates are estimated in the IGS05 realization | | coordinates | of the ITRF2005. The datum is realized by tightly | | | constraining (i.e. 0.1mm) the processed Reference Frame| | | stations to their current coordinate values. | |---------------------------------------------------------------------------| | Satellite clocks | A priori: broadcast clocks | | | | | | Estimation: Zero-difference data analysis | | | Satellite and receiver clock corrections are computed | | | on the basis of the double-difference orbit and ERP. | | | The generation of high-rate clock results is performed | | | in the following 2 steps: | | | 1. Least-squares adjustment with a sampling of 5 min | | | using phase and code observations. | | | 2. Interpolation from 5 min to 30 sec using phase. | |---------------------------------------------------------------------------| | Receiver clocks | A priori: receiver clocks are synchronized during | | bias | preprocessing using the pseudorange meas. | | | Estimation: see 'Satellite clocks' above | |---------------------------------------------------------------------------| | Orbital | 6 Keplerian elements plus 9 solar radiation parameters | | parameters | (Beutler 1994) at start of arc. | | | - Constant term in D-, Y- and X-directions | | | - Periodic terms in D-, Y- and X-directions | | | | | | A priori orbits are taken from (1)our last Ultra Rapid | | | orbit prediction, (2)the last IGS Ultra Rapid orbit | | | prediction or (3)the current broadcast orbit. | | | Whenever problem in long-arc occurs, the correspoding | | | orbit arc is splitted. | |---------------------------------------------------------------------------| | Satellite | Not estimated. | | attitude | | |---------------------------------------------------------------------------| | Troposphere | Zenith delay: Continuous piece-wise linear troposphere | | | zenith delay parameters are estimated | | | for each station with intervals of 1 | | | hour. Absolute/relative constraints of | | | 5m/3.5mm are applied. | | |--------------------------------------------------------| | | Mapping function: Dry Niell | | |--------------------------------------------------------| | | Zenith delay epochs: 00:00, 01:00, ..., 22:00, 23:00 | | |--------------------------------------------------------| | | Gradients: not estimated | | |--------------------------------------------------------| | | Mapping function: Dry Niell | |---------------------------------------------------------------------------| | Ionospheric | Not estimated (ionosphere-free based analysis) | | corrections | | |---------------------------------------------------------------------------| | Ambiguity | Ambiguities are resolved in a baseline-by-baseline | | | or network mode in 6-hour batches: | | | 1. Wide-lane : SIGMA strategy using the Melbourne- | | | Wubbena linear combination | | | 2. Narrow-lane: SIGMA strategy using the L3 ionosphere| | | free linear combination | |---------------------------------------------------------------------------| |*Earth Orient. | X- and Y-pole coordinates, and UT1-UTC represented | | Parameters (EOP) | with continuous piece-wise linear function using | | | 30-32h time resolution. The UT1-UTC value at the | | | beginning of the 30-32h arc is fixed using to the | | | current Bulletin A value. | | | 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 | |---------------------------------------------------------------------------| | Berg, H., Allgemeine Meteorologie, Duemmlers Verlag, Bonn, 1948. | | | | 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. | | | | Niell, A.E. (1996), Global Mapping Functions for the Atmosphere Delay at | | Radio Wavelengths, Journal of Geophysical Research, 101(B2), 3227-3246. | | | | 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. | | | | | ============================================================================= ============================================================================= |* = strong consistency with IERS/IGS conventions is especially important | | for these items | =============================================================================