The ULR6a GPS solution is a preliminary version of the reanalysis of 19 years of GPS data from 1995 to 2014 that has been undertaken within the framework of the 2nd data reprocessing campaign of the International GNSS Service (IGS). Its associated vertical velocity field is expressed in ITRF2008.
Double-differenced ionosphere-free GPS carrier phase observations from a global network of 754 stations were reanalyzed using GAMIT/GLOBK software version 10.5. The data set covered the period January 1995 to December 2013. Station coordinates, satellite orbits, Earth orientation parameters (EOPs), and zenith tropospheric delay parameters every hour, were estimated. The data analysis strategy (models, corrections...) was compliant with the specifications adopted by the IGS for this reanalysis (more information here). Details can also be found in the IGS-like ULR analysis centre form associated with this solution.
The GPS velocities were obtained in the final step of the analysis which combined the daily GAMIT/GLOBK global network solutions (station coordinates with full co-variances) from the entire data time span into a long-term solution using CATREF software. This long-term solution (ULR6a) was aligned to ITRF2008 using minimal constraints over a selected set of IGS Reference Frame stations. A detailed description can be found in the reference below.
Analysis center: | ULR | Number of stations: | 674 |
Solution: | ULR6a | CGPS@TG | 482 |
Date of publication: | 2016 | Reference Frame | 194 |
Time span: | 1995.0 - 2013.9 | Others | 77 |
Reference Frame: | ITRF 2008 |
Estimated (robust) velocities: | 493 |
CGPS@TG | 349 |
Average of formal errors: | 0.54 mm/yr |
Median of formal errors: | 0.36 mm/yr |
To assign more realistic uncertainties on the GPS velocities, the noise content in the position time series was examined by the maximum likelihood estimation (MLE) technique using CATS software (Williams, 2008). Time series were detrended at the CATREF stage. Details on the GPS velocity uncertainty assessment are given in the reference below.
Vertical velocities table
The ULR6a_Vertical-Velocities_Table provides the vertical GPS velocities and uncertainties for the 497 stations fulfilling the criteria of 3 years of minimum length without discontinuities and with data gaps not exceeding 30%.
Daily residual time series
The ULR6_detrend.zip file contains individual station data files of daily residual position time series in ITRF2008 with respect to the linear long-term combined solution at the reference epoch. These residuals (detrended) are expressed in meters in the local frame (North, East, and Up). The reference position and the 3D velocity in the local coordinate system (East, North, Up) are provided in the header of each file.
Position discontinuities
The ULR6a_discontinuities_Table.txt file provides the position offsets that were estimated.
Solution file
The long-term solution ULR6a in SINEX format (567 Mo) can be downloaded too. However, we recommend its use only to those familiar with SINEX files, and having a good geodetic background and experience.
The ULR5 GPS solution is the result of a reanalysis of 16 years of GPS data from 1995 to 2010. Its vertical velocity field is published in Global and Planetary Change. It is expressed in ITRF2008.
Double-differenced ionosphere-free GPS carrier phase observations from a global network of 420 stations were reanalyzed using GAMIT/GLOBK software version 10.4. The data set covered the period January 1995 to December 2010 and 282 stations out of 420 were co-located with a tide gauge. Station coordinates, satellite orbits, Earth orientation parameters (EOPs), and zenith tropospheric delay parameters every hour, were estimated. Details on the GPS data processing strategy (models, corrections,...) can be found in the IGS-like ULR analysis centre form associated with this solution.
The GPS velocities were obtained in the final step of the analysis which combined the weekly GAMIT/GLOBK global network solutions (station coordinates with full co-variances) from the entire data time span into a long-term solution using CATREF software. This long-term solution (ULR5) was aligned to ITRF2008 using minimal constraints over a selected set of IGS Reference Frame stations. A detailed description can be found in the reference below.
Analysis center: | ULR | Number of stations: | 420 |
Solution: | ULR5 | CGPS@TG | 282 |
Date of publication: | 2012 | Reference Frame | 191 |
Time span: | 1994.0 - 2010.9 | Others | 6 |
Reference Frame: | ITRF 2008 |
Estimated (robust) velocities: | 326 |
CGPS@TG | 232 |
Average of formal errors: | 0.36 mm/yr |
Median of formal errors: | 0.28 mm/yr |
To assign more realistic uncertainties on the GPS velocities, the noise content in the position time series was examined by the maximum likelihood estimation (MLE) technique using CATS software. Time series were detrended and deseasoned (annual cycles) at the CATREF stage. Details on the GPS velocity uncertainty assessment will be given in the below-mentioned paper.
Vertical velocities table
The ULR5_Vertical-Velocities_Table provides the vertical GPS velocities and uncertainties for the 326 stations fulfilling the criterias of 3 years of minimum length without discontinuities and with data gaps not exceeding 30%.
Weekly residual time series
The ULR5_detrend.zip file contains individual station data files of weekly residual position time series in ITRF2008 with respect to the linear long-term combined solution at the reference epoch. These residuals (detrended and deseasoned) are expressed in meters in the local frame (North, East, and Up). The reference position and the 3D velocity in the local coordinate system (East, North, Up) are provided in the header of each file. The ulr5.kmz file shows a Google Earth presentation of the above weekly data files by cliking on a station symbol. The associated IGS-like sitelog can be accessed too, as well as a plot of the residual position time series in the vertical.
Position discontinuities
The ULR5_discontinuities_Table.txt file provides the position offsets that were estimated.
Solution file
The long-term solution ULR5 in SINEX format (250 Mo) can be downloaded too. However, we recommend its use only to those familiar with SINEX files, and having a good geodetic background and experience.
ULR5 on Google Earth
The ULR5_Vertical_Velocites.kmz file shows a Google Earth presentation of the ULR5 vertical velocities. For each GPS station a vertical cylinder whose height is proportionnal to the estimated velocity is drawn ( yellow for subsidence, red for uplift).
The ULR4 GPS solution is the result of a reanalysis of 13 years of GPS data from 1996 to 2008. Its vertical velocity field is published in Journal of Geophysical Research. It is expressed in ITRF2005.
Double-differenced ionosphere-free GPS carrier phase observations from a global network of 316 stations were reanalyzed using GAMIT/GLOBK software version 10.34. The data set covered the period January 1996 to December 2008 and 216 stations out of 316 were co-located with a tide gauge. Station coordinates, satellite orbits, Earth orientation parameters (EOPs), and zenith tropospheric delay parameters every 2 hours, were estimated. Details on the GPS data processing strategy (models, corrections,...) can be found in the IGS-like ULR analysis centre form associated with this solution.
The GPS velocities were obtained in the final step of the analysis which combined the weekly GAMIT/GLOBK global network solutions (station coordinates with full co-variances) from the entire data time span into a long-term solution using CATREF software. This long-term solution (ULR4) was aligned to ITRF2005 using minimal constraints over a selected set of IGS Reference Frame stations. A detailed description can be found in the reference below.
Under construction...
To assign more realistic uncertainties on the GPS velocities, the noise content in the position time series was examined by the maximum likelihood estimation (MLE) technique using CATS software. Time series were detrended and deseasoned (annual cycles) at the CATREF stage. Details on the GPS velocity uncertainty assessment will be given in the below-mentioned paper.
Vertical velocities table
The ulr4_vertical-velocities_table provides the vertical GPS velocities and uncertainties for the 275 stations fulfilling the criterias of 2.5 years of minimum length without discontinuities and with data gaps not exceeding 30%.
Weekly residual time series
The ulr4_detrend.zip file contains individual station data files of weekly residual position time series in ITRF2005 with respect to the linear long-term combined solution at the reference epoch. These residuals (detrended and deseasoned) are expressed in meters in the local frame (North, East, and Up). The reference position and the 3D velocity in the local coordinate system (East, North, Up) are provided in the header of each file. Theulr4.kmz file shows a Google Earth presentation of the above weekly data files by cliking on a station symbol. The associated IGS-like sitelog can be accessed too, as well as a plot of the residual position time series in the vertical.
Position discontinuities
The ulr4_discontinuities_table.txt file provides the position offsets that were estimated.
Solution file
The long-term solution ULR4 in SINEX format (47 Mo) can be downloaded too. However, we recommend its use only to those familiar with SINEX files, and having a good geodetic background and experience.
A. Santamaria-Gomez, M. Gravelle, X. Collilieux, M. Guichard, B. Martin Miguez, P. Tiphaneau, G. Wöppelmann (2012) : Mitigating the effects of vertical land motion in tide gauge records using a state-of-the-art GPS velocity field. Global and Planetary Change, Vol. 98-99, pp. 6-17.