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Introduction to JPL's GNSS Time Series

Edited Time Series, Velocity Field, and Web SiteM. Heflin

Point PositionsA. Moore

Orbits and ClocksD. Murphy, S. Desai, W. Bertiger, B. Haines, D. Kuang, A. Sibthorpe,

A. Sibois, P. Ries, D. Hemberger, A. Dietrich

The research described herein was performed at the Jet Propulsion Laboratory of the California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Government sponsorship acknowledged. Copyright 2019 © California Institute of Technology.

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GNSS Time Series - Four Basic Steps

Step 1 – Orbits and ClocksGet data from roughly eighty global GNSS receiversCompute precise GNSS orbits and clocks in NNR GNSS reference frameCompute transformation parameters from NNR GNSS frame to IGS14

Step 2 - Point PositionsCompute point positions for thousands of global GNSS receivers in NNR GNSS reference frameResolve phase ambiguitiesApply transformation parameters to obtain positions in IGS14

Step 3 – Time SeriesSearch for breaksRemove outliersEstimate positions, velocities, breaks, and seasonal parameters

Step 4 – Web SiteCreate tables and plots which are posted on the web siteCreate edited time series and residuals which can be downloaded

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Step 1 – Orbits and Clocks

Input DataDaily rinex files from roughly eighty global GNSS receivers

Fit ParametersSatellite initial conditions, non-gravitational forces, and clocks.Receiver positions and clocks except for one reference clockReceiver tropospheric zenith delays and gradientsPolar motion, polar motion rate, and UT rateTransformation parameters from NNR GNSS frame to IGS14Resolved phase ambiguities

ModelsGravity from Earth, Sun, Moon, and other planetsDE421 planetary ephemerisGSPM10 satellite solar pressure modelGYM95 satellite yaw modelIAU06 model for precession and nutationIERS2010 tidesFES2004 ocean loadingIGS satellite and receiver antenna phase center modelsGPT2w tropospheric mapping functions and nominals2nd order ionospheric corrections applied7 degree elevation angle cutoff

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Step 2 - Point Positions

Input DataDaily rinex files for thousands of global GNSS receiversSatellite orbits from step 1Satellite clocks from step 1Phase ambiguities from step 1Transformation parameters from step 1

Fit ParametersReceiver tropospheric zenith delay and gradientsReceiver positionReceiver clocksResolved phase ambiguities

Reference FrameNNR orbits and clocks are used for point positioningTransformation parameters from step 1 are applied to obtain position estimates in IGS14

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Step 3 - Time Series

Input dataDaily GNSS point positions

Fit ParametersReceiver positionsReceiver velocitiesReceiver breaksReceiver seasonals

BreaksCHI^2 is computed with and without each break candidate and those with F > 150 are acceptedF = [(Chi^2(without) – Chi^2(with))/Chi^(with)] * [(ndata – pwith)/(pwith-pwithout)]ndata is the number of position observations being fitpwith is the number of parameters with the break includedpwithout is the number of parameters without the break included

OutliersPoints with formal errors > 5 mm in any component

Error ScalingParameter errors multiplied by 20 to make them consistent with one sigma data decimation results

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Step 4 - Web Site

Web Launch dateNovember 29, 1994

ImplementationHTMLKMLJavascript

InterfaceGoogle mapList of sites

TablesPositionsVelocitiesBreaksSeasonalsMethods

DownloadTime seriesResiduals

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Formats and Plots

Time Series and Residual FormatColumn 1: Decimal_YR Columns 2-4: East(m) North(m) Vert(m) Columns 5-7: E_sig(m) N_sig(m) V_sig(m) Columns 8-10: E_N_cor E_V_cor N_V_corColumn 11: Time in Seconds past J2000Columns 12-17: Time in YEAR MM DD HR MN SS

ObservationsBlack points with error bars

FitRed points

BreaksGreen bars

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Download Instructions

Download edited time series for a single siteClick “Time Series” on web siteRight click site of interestChoose “Download Linked File”

Download residual time series for a single siteClick “Residuals” on web siteRight click site of interestChoose “Download Linked File”

Download all edited time serieswget -r -nd -np -R "index.html*" -A "*.series" "https://sideshow.jpl.nasa.gov/pub/JPL_GNSS_Timeseries/repro2018a/post/point" .

Download all residual time serieswget -r -nd -np -R "index.html*" -A "*.resid" "https://sideshow.jpl.nasa.gov/pub/JPL_GNSS_Timeseries/repro2018a/post/resid" .