|============================================================================ | | | | | NGL/UNR GPS Data Analysis Strategy and Products Summary | | | | Current Label: GipsyX-2.3/IGS20 of 2024-08-25 | | | | Please cite: Blewitt et al. (2018) -- see References below | |===========================================================================| |ANALYSIS CENTER | Nevada Geodetic Laboratory | | | University of Nevada, Reno | | | 1664. N. Virginia St | | | MS 178 | | | Reno, NV 89557 | | | United States | | | Data Archives: | | | http://geodesy.unr.edu/ | |---------------------------------------------------------------------------| |CONTACT PERSONS | Dr. Geoffrey Blewitt | | | E-mail: gblewitt (at) unr.edu | | | | | | Dr. Bill Hammond | | | E-mail: whammond (at) unr.edu | | | | | | Dr. Corné Kreemer | | | E-mail: kreemer (at) unr.edu | |---------------------------------------------------------------------------| |SOFTWARE USED | Developed at JPL: GipsyX-2.3 | | | Developed at UNR: pppZap, pppTrop, wet2vapor, pppKenv| | | pppQA, pppCluster, ppp2Products, tenv3Plate, midas | | | Developed at UNAVCO: teqc Version 2018Oct15 | |---------------------------------------------------------------------------| |NGL SITE TIME SERIES| http://geodesy.unr.edu/gps_timeseries/ | | SSSS = site ID | txyz/IGS20/SSSS.txyz2 final daily x,y,z | | | tenv3/IGS20/SSSS.tenv final daily e,n,v | | PP = plate ID | tenv3/plates/PP/SSSS.PP.tenv final plate e,n,v | | YYYY = year | kenv/SSSS/SSSS.YYYY.kenv.zip final 5-min e,n,v | | | qa/SSSS.qa.gz final QA time series| | | trop/SSSS/SSSS.YYYY.trop.zip final tropo SINEX | | | rapids/tenv3/FID/SSSS.FID.tenv3 rapid daily e,n,v | | | rapids_5min/kenv/by_sta/SSSS.kenv.tar | | | rapid 5-min e,n,v | | | txyz2 -> tenv3 transformation given by Blewitt(2024) | |---------------------------------------------------------------------------| |NGL SITE VELOCITIES | http://geodesy.unr.edu/velocities/ | | | midas.IGS20.txt IGS20 | | PP = plate ID | midas.PP.txt Plate-fixed | |---------------------------------------------------------------------------| |FORMAT README FILES | http://geodesy.unr.edu/ | | | gps_timeseries/README.tenv3.txt | | | gps_timeseries/README.txyz2.txt | | | gps_timeseries/README.kenv.txt | | | gps_timeseries/QA.pdf | | | README_trop.txt | | | velocities/midas.readme.txt | |---------------------------------------------------------------------------| |PRODUCTS USED | Final, NNR daily IGS20 products from JPL archive: | | | https://sideshow.jpl.nasa.gov/pub/ | | | JPL_GNSS_Products/Final/ | | | Including: | | | GPS satellite orbit position/velocity estimates | | | GPS satellite clock estimates | | | GPS satellite attitude parameters | | | WLPB estimates (widelane & phase biases) | | | Daily transformation parameters from NNR to IGS20 | | | Time-pole parameter estimates | | | GPS satellite eclipse shadow times | | | Name of IGS antenna calibration files | | | IONEX data from JPL for higher order ion calibrations| | | https://sideshow.jpl.nasa.gov/pub/iono_daily/ | | | IONEX_final/ | | | VMF1 gridded ECMWF tropo parameters from TU Vienna | | | http://vmf.geo.tuwien.ac.at/trop_products/GRID/ | | | 2.5x2/VMF1/STD_OP/ | | | Auxiliary data updated periodically from JPL: | | | https://sideshow.jpl.nasa.gov/pub/gipsy_products/ | | | gipsy_params/ | | | IGS ANTEX antenna calibration file | | | JPL DE421 planetary ephemeris | | | CODE CA-P DCB (differential code biases) | | | GPS receiver type codes | | | GPS constellation configuration history | | | IERS/BIH leap seconds history | | | IERS earth orientation parameters | | | NOAA IGRF12 Earth magnetic field model | | | Auxiliary data updated from IGS Central Bureau: | | | https://igscb.jpl.nasa.gov/igscb/station/general/ | | | igs_with_former.snx | | | IGS station receiver/antenna configuration history| | | Auxiliary data custom generated by JPL: | | | GOT4.8ac ocean tidal loading coefficients at sites | | | Auxiliary data from Chalmers University, Sweden: | | | http://holt.oso.chalmers.se/loading/ | | | GOT4.8 ocean tidal loading coefficients at sites | | | Custom data (from NGL/UNR) | | | http://geodesy.unr.edu/NGLStationPages/steps.txt | | | Step discontinuity database | | | http://geodesy.unr.edu/NGLStationPages/llh.out | | | Approximate latitude, longitude, height at sites | | | Internal: antenna+radome and receiver type aliases | |---------------------------------------------------------------------------| |GPS DATA USED: | RINEX files from various archives, including: | | | UNAVCO https://gage-data.earthscope.org | | | CDDIS ftps://gdc.cddis.eosdis.nasa.gov | | | CORS https://noaa-cors-pds.s3.amazonaws.com | | | SIO ftp://garner.ucsd.edu | | | EUREF https://igs.bkg.bund.de/root_ftp/EUREF | | | GEONET https://data.geonet.org.nz | | | RGP ftp://rgpdata.ign.fr | | | AUSTRALIA sftp://sftp.data.gnss.ga.gov.au | | | GSI ftp://terras.gsi.go.jp | | | SONEL ftp://ftp.sonel.org | | | ...and many more | |---------------------------------------------------------------------------| |PREPARATION DATE | 2024-10-27 for NGL's GipsyX-2.3/IGS20 products | |---------------------------------------------------------------------------| |MODIFICATION DATES | 2019-12-17 initial creation | |---------------------------------------------------------------------------| |EFFECTIVE DATE FOR | 2024-10-27 updated website http://geodesy.unr.edu | |DATA ANALYSIS | NGL GipsyX-2.3/IGS20 products using JPL IGS20products| ============================================================================= ============================================================================= | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Preprocessing | RINEX header must be interpretable | | | - approximate XYZ replaced with NGL database values | | | - alias table interprets antenna type as IGS standard| | | - algorithm attempts to fix formatting errors | | | - require antenna type has IGS ANTEX calibrations | | | - non-calibrated radome set to "NONE" (IGS standard) | | | Require minimum file size, typically ~18 hr/day | | | Apply CA-P1 biases | | | Fix non-compliant time-tags for older receiver types | | | Remove non-GPS GNSS data (e.g., GLONASS) | | | Remove L2C and C2 data | | | Cycle slip detection and correction using TurboEdit | | | Delete phase connected arcs < 20 minutes | | | Carrier Phase: Decimated to 5 minutes | | | Pseudorange: Carrier-aided smoothing to 5 minutes | |---------------------------------------------------------------------------| | Basic Observable | Undifferenced ionosphere-free carrier phase, LC | | | Undifferenced ionosphere-free pseudorange, PC | | |--------------------------------------------------------| | | Elevation angle cutoff: 7 degrees | | | Sampling rate: 5 minutes | | | Data weight, LC: 0.01 m | | | Data weight, PC: 1 m | | | Elevation weighting: Sigma^2=1/sin(e) | |---------------------------------------------------------------------------| | Modeled | Undifferenced LC and PC combinations | | observable | CA-P1 biases from CODE applied | |---------------------------------------------------------------------------| | RHC phase | Applied | | rotation corr. | | |---------------------------------------------------------------------------| | Marker -> antenna| dN, dE, dU eccentricities from IGS SNX or RINEX header | | ARP eccentricity | applied to compute station marker coordinates | |---------------------------------------------------------------------------| | Ground antenna | PCV model from igs14_wwww.atx applied | | phase center cal.| Receiver antenna and radome types from RINEX header | |---------------------------------------------------------------------------| | Troposphere | A priori model: Wet and Dry interpolated from VMF1 grid| | | Nominal gradients are zero | | | Mapping Function: Vienna Mapping Function VMF1 | | | Estimation: Zenith delay and gradients as random walk | | | every 5 minutes | | | Integrated water vapor: from wet zenith delay using | | | Bevis et al. (1994) refractivity coeffs, SI units:| | | k1=0.776, k2=0.704, k3=3739.0, Rv = 461.5 and | | | k2'=k2-k1*m where ratio m = 18.0152/28.9644 and | | | using VMF1 interpolated mean atmospheric temperature | |---------------------------------------------------------------------------| | Ionosphere | 1st order effect: Removed by LC and PC combinations | | | 2nd order effect: Modeled using IONEX data with IGRF12 | |---------------------------------------------------------------------------| | Plate motions | Not applied to apriori positions | | | Reference velocities for plate-fixed time series use | | | rotation pole vectors from Kreemer et al. (2014) | |---------------------------------------------------------------------------| | Tidal | Solid earth tide: IERS 2010 Conventions | | |--------------------------------------------------------| | | Permanent tide: Not removed from model | | |--------------------------------------------------------| | | Pole tide: IERS 2010 Conventions | | |--------------------------------------------------------| | | Ocean Tide Loading: | | | Diurnal, Semidiurnal, MF, and MM Model: FES2004 | | | Semiannual: Self-consistent equilibrium model | | | hardisp.f from IERS2010 | | | | | | Surface deformations computed with respect to | | | instantaneous center of mass | | |--------------------------------------------------------| | | Ocean Pole Tide Loading: Applied | |---------------------------------------------------------------------------| | Non-tidal | Atmospheric Pressure: Not applied | | loading |--------------------------------------------------------| | | Ocean Bottom Pressure: Not applied | | |--------------------------------------------------------| | | Surface Hydrology: Not applied | | |--------------------------------------------------------| | | Other Effects: None applied | |---------------------------------------------------------------------------| | Earth Orientation| IERS 2010 Conventions for diurnal, semidiurnal, and | | Parameter (EOP) | long period tidal effects on polar motion and UT1 | | Model | | |---------------------------------------------------------------------------| | Satellite center | Phase centers offsets from igs20_wwww.pcm applied | | of mass | | | correction | | |---------------------------------------------------------------------------| | Satellite antenna| PCV model w.r.t. phase center from igs20_www.atx | | phase variations | applied | |---------------------------------------------------------------------------| | Relativistic | Periodic Clock Corrections, (-2*R*V/c): Applied | | corrections | Shapiro Delay: Applied | ----------------------------------------------------------------------------- | GPS Attitude | GYM95 nominal yaw rate model from Bar-Sever (1996) and | | model | yaw rates estimated for Block II satellites | ============================================================================= ============================================================================= | ORBIT MODELS (JPL ORBIT PRODUCTS) | |---------------------------------------------------------------------------| | Orbit Arc | 30 hours | |---------------------------------------------------------------------------| | Geopotential | EGM2008 12x12 | | | C20, C30, C40, C21, S21 from IERS2010 standards | | |--------------------------------------------------------| | | GM = 398600.4415 km**3/sec**2 | | |--------------------------------------------------------| | | AE = 6378.1363 km | |---------------------------------------------------------------------------| | Third-body | Sun, Moon, and All Planets | | |--------------------------------------------------------| | | Ephemeris: JPL DE421 | |---------------------------------------------------------------------------| | Solar radiation | Block II/IIA/IIF/IIR/III: JPL empirical model, GSPM-13 | | pressure | Bar-Sever and Kuang, (2004) | | | Sibois et al, 2014 | | |--------------------------------------------------------| | | Estimate GPS "Y-Bias" and solar radiation pressure(SRP)| | | coefficient as constant with no a-priori constraint. | | | Make small time-varying (stochastic) adjustments to SRP| | | coefficients in spacecraft body-fixed X and Z | | | directions (1% process noise sigma with 1 hr 11 sec | | | updates and 4-hour correlation time.) Estimate tightly | | | constrained time-varying empirical acceleration in | | | spacecraft Y direction (0.01 nm/s^2 process noise | | | sigma with 1 hr 11 sec updates and 4-hour correlation | | | time.) | | |--------------------------------------------------------| | | Earth shadow model: conic model with oblate Earth, | | | umbra and penumbra | | |--------------------------------------------------------| | | Earth albedo: applied (Knocke, 1989) | | |--------------------------------------------------------| | | Attitude Model: GYM95 yaw model from Bar-Sever (1996) | |---------------------------------------------------------------------------| | Tidal forces | Solid earth tides: IERS 2010 Conventions | | |--------------------------------------------------------| | | Ocean tides: GOT4.8ac to degree and order 30 | | | with convolution formalism of Desai and | | | and Yuan (2006) | | |--------------------------------------------------------| | | Solid Earth Pole tide: IERS 2010 conventions | | |--------------------------------------------------------| | | Ocean Pole tide: IERS 2010 conventions | |---------------------------------------------------------------------------| | Relativity | Applied | | | Acceleration due to point mass of Earth | | | Acceleration due to geodesic precession | | | Acceleration due to Lense-Thirring precession | |---------------------------------------------------------------------------| | Numerical | Variable high order Adams predictor-corrector | | Integration | with direct integration of second-order equations | | |--------------------------------------------------------| | | Integration step: variable | | |--------------------------------------------------------| | | Starter procedure: RKF | | |--------------------------------------------------------| | | Arc length: 30 hours centered at 12:00 of each day | ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | ESTIMATED PARAMETERS (APRIORI VALUES & SIGMAS) | |---------------------------------------------------------------------------| | Adjustment | Stochastic Kalman filter/smoother implemented as | | | square root information filter with smoother | |---------------------------------------------------------------------------| | Station | Daily PPP estimates for all sites | | coordinates | Apply daily transformation into IGS20 | |---------------------------------------------------------------------------| | Satellite clock | Fixed to JPL clock products, which are given every | | | 5 minutes relative to reference clock | |---------------------------------------------------------------------------| | Receiver clock | Estimate every 5 minutes relative to satellite clocks | |---------------------------------------------------------------------------| | Orbital | Fixed to JPL ECEF orbit products interpolated to 5 min | |---------------------------------------------------------------------------| | GPS Attitude | Fixed to JPL products: yaw rates when in eclipse | |---------------------------------------------------------------------------| | Troposphere | Zenith delay: random walk 1.0d-7 km/sqrt(sec) | | | Horizontal delay gradients: random walk 1.0e-8 | | | km/sqrt(sec), as recommended by Young et al. (2024) | | |--------------------------------------------------------| | | Mapping function: VMF1 | |---------------------------------------------------------------------------| | Ionosphere | 1st order effects removed by LC and PC combinations | | | and 2nd order effects modeled | |---------------------------------------------------------------------------| | Ambiguity | Resolve ambiguities using WLPB products from JPL | |---------------------------------------------------------------------------| | Earth Orientation| Fix to JPL products: polar motion, polar motion rate, | | Parameters | and LOD, where UT1 is integrated from estimated LOD | ============================================================================= ============================================================================= | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Inertial | J2000 Geocentric | |---------------------------------------------------------------------------| | Terrestrial | Daily transformed coordinates into IGS20 and | | | relevant plate-fixed frames using plate rotation model | | | of Kreemer et al. (2014) | |---------------------------------------------------------------------------| | Interconnection | Precession: IAU 2006 Precession Theory | | |--------------------------------------------------------| | | Nutation: IAU 2006 Nutation Theory | | |--------------------------------------------------------| | | A priori EOPS: EOPC04 updated daily, with | | | polar motion and length of day estimated daily | ============================================================================= ============================================================================= | REFERENCES | |---------------------------------------------------------------------------| | Bar-Sever, Y. E. (1996), "A new model for GPS yaw attitude", Journal of | | Geodesy, 70:714-723 | | | | Bar-Sever, Y. E., and D. Kuang (2004), New empirically-derived solar | | radiation pressure model for GPS satellites, IPN Progress Reports | | 42-159, JPL. Available online: | | http://ipnpr.jpl.nasa.gov/progress_report/42-160/title.htm | | | | Bassiri, S., and G. A. Hajj, (1993), Higher-order ionospheric effects on | | the global positioning systems observables and means of modeling them, | | Manuscripta Geodtica, 18, 280-289, 1993 | | | | Bevis M., S. Businger, S. Chiswell, T.A. Herring, R.A. Anthes, C. Rocken, | | and R.H. Ware (1994), GPS meteorology: Mapping zenith wet delays onto | | precipitable water. Journal of Applied Meteorology, Vol. 33, p.378-386 | | | | Blewitt, G., (2024), An improved equation of latitude and a global system | | of graticule distance coordinates. Journal of Geodesy, 98(6) | | https://doi.org/10.1007/s00190-023-01815-0 | | | | Blewitt, G., (1990), An automatic editing algorithm for GPS data. | | Geophysical Research Letters, Vol. 17, No. 3, p. 199-202 | | | | Blewitt, G., W.C. Hammond, and C. Kreemer (2018), Harnessing the GPS data | | explosion for interdisciplinary science. Eos, Vol. 99, | | https://doi.org/10.1029/2018EO104623 | | | | IERS Conventions 2003, D.D. McCarthy & G. Petit (editors), IERS Technical | | Note 32, Frankfurt am Main: Verlag des Bundesamts fuer Kartographie und | | Geodaesie, 2004. | | | | Kedar, S., G. Hajj, B. Wilson, and M. Heflin (2003), The effect of the | | second order GPS ionospheric correction on receiver positions, Geophys. | | Res. Lett., 30(16), 1829, doi:10.1029/2003GL017639 | | | | Kreemer, C., G. Blewitt, and E. Klein (2014), A geodetic plate motion and | | Global Strain Rate Model. Geochemistry, Geophysics, Geosystems, Vol.15 | | pp. 3849-3889, doi:10.1002/2014GC005407 | | | | Moyer, T.D., (2000) Formulation of observed and computed values of deep | | space network data types for navigation, Deep Space Communications and | | Navigation Series, Jet Propulsion Laboratory, California Institute of | | Technology, Pasadena, CA, Chapter 4, pp, 19-28. | | | | Sibois, A., C. Selle, S. Desai, A. Sibthorpe, and J. Weiss, GSPM13: An | | updated empirical model for solar radiation pressure forces acting on | | GPS satellites, IGS Workshop 2014, Pasadena, CA, 2014. | | | | Young, Z.M., G. Blewitt, C. Kreemer (2024). Improved GPS tropospheric path| | delay estimation using variable random walk process noise. | | Journal of Geodesy, 98(89), https://doi.org/10.1007/s00190-024-01898-3 | =============================================================================