The end of 1994. The author decided to develop a flexible, efficient and user-friendly software for his research work. The primary motivation was to develop an efficient tool to combine data from more than 1000 sites simultaneously and to combine GPS and SAR data more rigorously. The basic considerations were:
1. Dealing with quasi-observations only.1995. The UCLA geodesy group started to use the software (called JPLS during that time) for the velocity map in Southern California and provided beta tests for the software.
2. Using Kalman filter (covariance matrix approach).
3. Adopting various formats from various software outputs.
4. Open structure for further development.
5. Focusing on speed and space-saving.
6. Graphic user interface in the future.
1996.2. The software was named as QOCA (Quasi-Observation combination Analysis) and the first version was born. (Version 1.01)
1996.5. Extended Kalman filtering mode to both forward and backward filtering. Set the coseismic parameter estimation choice: explicit or implicit. (Version 1.03)
1997.2. Added baseline vector choice: either input or output. Added postseismic deformation models. (Version 1.05)
1997.5. The online graphic manual package QOCAVIEW was developed. This package was developed using Tcl/Tk.
1997.10. Modified logarithmic postseismic deformation model. Added internal constraints. Allowed coseismic deformation parameters by sites with 4 choices: (1) implicit coor + implicit velo. (2) implicit coor + explicit velo. (3) explicit coor + implicit velo. (4) explicit coor + explicit velo. (Version 1.07)
1998.1. Added de-jump and de-constraint options. (Version 1.09)
1998.2. Added more options of the internal constraints (Version 1.10)
1998.3. Completed the robust fit algorithm (Version 1.11)
1998.4. The theoretical frame of QOCA was published (see Dong et al., 1998).
1998.6. Version 1.13 with offset correction option.
1998.8. QOCAVIEW is replaced by on-line web manual. You are looking at the work right now!
1999.1. Win NASA award for the creative work.
1999.4. Version 1.17 with modified library.
1999.6. Add function to perform pole tide, ocean tide and atmospheric loading correction.
1999.8. Add function of phase center correction.
2000.2. Can transfer Bernese neq file (binary or ascii format) to QOCA qob file directly. The byte swap function is also realized.
2001.1. Version 1.23. Original utility mk_eq_tbl is no longer supported. Package faultview is partly fulfiled. The apriori coseismic displacement table can be generated by faultview.
2002.4. Dong et al., (2002) is published, which describes the application of QOCA in site position time series analysis.
2003.1. QOCA will add a very important package st_filter, which performs spatio-temporal filtering to quasi-observation time series and is able to estimate source parameters (such as fault slip rate and magma volume) directly. Currently, we start to design the new package.
2003.8. Add package mload to perform calculation of mass loading induced site displacements using Green's function approach (version 1.27).
2003.9. QOCA wins 2003 NASA's Space Act Award (Major Award).
2004.7. The second generation of QOCA (version 2.0 caled st_filter) is formally used in NASA's REASoN project to combine SOPAC and JPL's SCIGN solutions to get combined SCIGN solutions. In this project, the orbit combination function of st_filter is first utilized. To test the reliability of st_filter combination, we compare the st_filter with the well-established GLOBK combination results. Under the same constraints and the same strategy, st_filter generates nearly identical results as the GLOBK output (for example: the site coordinate adjustments differ only at the 0.01-0.03 mm level, which are basically due to the machine rounding errors). We also compare the speed under the same machine, for 13 qob files, 385 sites and 27 satellites, GLOBK uses 516.27 elapsed seconds (88.1% usage), st_filter uses 389.75 elapsed seconds (87.0% usage). Since GLOBK uses the converted data file, st_filter uses the original data file (GAMIT h-file and GIPSY stacov file) directly and converts the data format inside the run, if the GLOBK run includes the data converting CPU time, the CPU difference should be even a little larger. Thus, the efficiency of st_filter is justified.
2005.2. One new package (pca) joins the QOCA software. The pca performs Principal Component Analysis (PCA) for the network site position time series. It has option to perform either SVD (Singular Value Decomposition), PCA or KLE (Karhunen-Loeve Expansion) decomposition. It has wide applications in tectonic research and spatio-temporal filtering.
Created by Danan Dong and maintained by Da Kuang for
Geodynamics and Space Geodesy Group
email: dakuang@jpl.nasa.gov tel:(818)354-8332
07/30/98
