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Summary of the Reanalysis of GPS DataPreliminary results, subject to change |
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WARNING!!! RESULTS SHOWN ON THIS PAGE ARE PRELIMINARY. POSITIONAL AND VELOCITY DISCONTINUITIES MAY BE MISSING, SO THE PURPOSE OF THIS SITE, AT THIS POINT IN TIME, IS TO PROVIDE INFORMATION ABOUT THE STATUS OF THE REPROCESSING AND FOR USERS TO POTENTIALLY PROVIDE FEEDBACK ABOUT INSTANCES WHERE KNOWN DISCONTINUITIES ARE MISSING FROM THE CURRENT RESULTS.
CATREF stacking of NGS Global and CORS SINEX files Our main use of CATREF is to stack the time series of reprocessed weekly SINEX files to obtain regularized coordinates and secular velocities for CORS stations, in a global framework aligned to the current International Terrestrial Reference Frame (ITRF)--i.e., ITRF2008. Stacking of the SINEX files happens in three main steps. The first step is the determination of weekly Helmert parameters that align each weekly SINEX file to the stacked frame while miminizing aliasing effects due to local non-linear motions. This first step is achieved by determining the weekly Helmerts over an optimal sampling of the globally distributed sites. The second step is the application of the weekly Helmerts to the full network to obtain regularized coordinates and velocities for the sites in the full network. Finally, the stacked TRF is aligned with ITRF2008. Step 1. Mitigating aliasing effects due to local non-linear motionsBelow are two columns of figures. The figures on the left are from the Global stacking and those on the right are from the CORS stacking. The first row of figures are maps showing the subnetworks used in determining the set of weekly Helmert parameters. The second row of figures contain time-series of the weighted-average of the coordinate residuals taken over the subnetwork. |
  CORS —
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 CORS —
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The plots below show the time series of weekly Helmert parameters derived by stacking the subnetwork. Translations in the X, Y and Z directions are denoted with Tx, Ty and Tz. Rotations about X, Y and Z are denoted with Rx, Ry and Rz. The change in scale, i.e., dS, is assumed to be zero for this step.
 CORS —
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 CORS —
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Step 2. Stacking of NGS TRF using Helmerts derived in Step 1
Below are again two columns of figures with the figures on the left being from the Global stacking and those on the right from the CORS stacking. The first row of figures are maps showing the sites common to ITRF2008 and the NGS SINEX files. The second row of figures contain time-series of the weighted-average of the coordinate residuals taken over the ITRF2008 sites (after applying the weekly Helmert parameters from above).
 CORS —
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 CORS —
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Step 3. Obtaining ITRF2008(NGS), i.e., Alignment of NGS TRF with ITRF2008
The maps below show the velocities in ITRF2008 and those derived from the NGS reprocessing and stacking (after aligning the stacked NGS solut ion to ITRF2008).
 CORS —
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