California Spatial Reference Center
High Precision Geodetic Network (HPGN) 2000
  Download HPGN/CACORS site coordinates:   ITRF97   NAD83

  Coseismic displacements induced by the Hector Mine Earthquake for all SCIGN stations.

  Velocities for additional California CORS stations that were not adjusted in CSRC's HPGN 1998 analysis.

Note: the above products were generated by CSRC and sanctioned by NGS in March 2001.

  Interactive map of all sites processed. Includes sites that were not sanctioned by the NGS due to a short period of record, marker reference point issues, or an undetermined height change during operation. Therefore, the sites on this map will differ from the CSRC Data Portal dynamic map of all NGS-sanctioned sites.


Background

The High Precision Geodetic Network (HPGN) was established by the California Department of Transportation (Caltrans) and the National Geodetic Survey (NGS) as a statewide GPS control network. The network was first visited in 1991 and re-occupied in 1992 and 1998. The HPGN network was displaced by the Mw = 7.1 earthquake near Hector Mine on October 16, 2000. As a result, a large number of stations were re-visited during a 12 day campaign in May 2000. The experiment was conducted using dual-frequency geodetic receivers and consisted of 61 stations. The California Spatial Reference Center (CSRC) was contracted as an independent consultant by Caltrans to analyze these data.

During the time of the experiment, a large number of continuously operated GPS stations were active in California, established by the Southern California Integrated GPS Network (SCIGN), the Bay Area Regional Deformation Network (BARD), the Continuously Operated Reference Stations (CORS), and the Jet Propulsion Laboratory (JPL).

The data were processed using the GAMIT and GLOBK packages, developed at Scripps Institution of Oceanography (SIO) and the Massachusetts Institute of Technology (MIT). The official SIO final orbits as submitted to the International GPS Service (IGS) were used, and tightly constrained to obtain the highest precision possible. The analysis was performed in a three step procedure. First, the California CORS stations were processed, together with a selected set of IGS stations, for each of the 12 days of the experiment. Secondly, the HPGN data were reduced together with data of 7 spatially distributed California CORS stations, to align the solution with a regional reference frame. Finally, the GLOBK package was used to combine the two sets of solutions together with the global SIO solution to obtain an estimate of station coordinates, averaged over the multi-day experiment. The regional reference frame is that of the National Spatial Reference System and defined by the following stations: CARR, WINT, MHCB, MONP, AOA1, CAT1, VNDP, D368 and D364. The parameters for these stations (coordinates & velocities) were provided by NGS and transformed from NAD83 to ITRF97 using the published transformation parameters. The reference frame was then imposed by performing an six parameter transformation on the loosely constrained CSRC solution to best fit the NSRS.

The final GLOBK adjustment included a total of 241 stations, of which 61 were part of the Hector Mine Survey (HPGN). The additional stations are all the California CORS that were active and healthy during the time of the survey. They include 91 stations that were not in CSRC's HPGN 1998 analysis and 140 stations that do not have NGS sanctioned coordinates yet. The daily coordinate repeatability of the 61 HPGN stations was 2.9/3.1/8.5 millimeters in North, East and Vertical direction, respectively.