[IGSMAIL-3635]: GPS Time Series Data Set

[Michael B Heflin]

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IGS Electronic Mail      05 Dec 10:58:19 PST 2001      Message Number 3635
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Author:  M B Heflin

An updated GPS time series data set is now available at URL:

http://sideshow.jpl.nasa.gov/mbh/series.html

Recent improvements include:
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1.  Time series for 653 GPS sites:  IGS, SCIGN, CORS, NBAR, and PANGA networks
2.  Time span 10.8 years:  91JAN22 through 01NOV03
3.  Station-days of GPS data:  605208
4.  Consistent reference frame for all results:  ITRF2000
5.  Reprocessed most days between 91JAN22 and 95APR05
6.  Web page upgraded to XHTML
7.  New position and velocity estimates
8.  Geocenter and scale time series
9.  Polar motion and length of day time series
10. Updated maps
11. Numerical results available via anonymous ftp

What scientific questions can this data set address?
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Global plate motion
Post-glacial rebound
Interseismic deformation in Southern California - compression in LA
Earthquake displacements - Landers, Northridge, Hector Mine, Arequipa
Seasonal loading variations - ground water, ocean, atmosphere
Angular momentum exchange - solid Earth, oceans, and atmosphere

How good are the various GPS estimates?
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IGS comparisons
Orbits                                      3  cm
Clocks                                    0.1  nsec
Polar Motion                         0.05-0.1  mas
Polar Motion Rate                     0.1-0.2  mas/day
Length of Day                       0.02-0.04  msec/day
Tropospheric Delay                        2-4  mm

Daily repeatability
Point Position NEV             3.7, 5.3, 10.1  mm
Recent Geocenter XYZ            1.0, 1.0, 1.5  cm 
Recent Scale                              0.3  ppb

Repeatability of velocities based on GPS data with time span T
Velocity NEV                    3.6, 4.5, 9.1  mm/T in years

Comparison with ITRF2000
Velocity NEV                    0.7, 0.7, 1.5  mm/yr

How is this data set generated?
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Retrieve data
Compute precise GPS orbits and clocks based on 42 sites per day
Post-process >500 sites per day with fixed precise orbits and clocks