California Spatial Reference Center
San Joaquin Valley Height Modernization Project
  • 2006: RFP# 0527RJB: The Northern San Joaquin Valley Height Modernization Project 2006
    Recon notes  |  Station list

    CORRECTION (03/10/2006)

    Continuous GPS sites WINT and P309 were added to the project during its final review and inadvertently left off the reconnaissance notes and the station list. They should be included in the project as Primary Base Stations. Station HPGN D CA 10 FK was mistakenly added to the map and was used as a place holder in the list of Primary Base Stations. The station was removed at the request of Caltrans due to safety considerations and thus is NOT part of the project and was not included on either the reconnaissance notes or station list. Station 109.28 should replace station 10 FK in the Primary Base Station list. PBO site P309 is not yet in the NGS data base as is the case with several PBO sites since they have not been included in any previous projects submitted to NGS. PBO indicates that the station is installed and operating.

    Not listing station HPGN CA 10 10 in the reconnaissance notes was an oversight. It is part of the project.

    The total station count is 140 (adding P309 and WINT to the existing station list).


  • 2004: This ambitious Height Modernization project encompasses the entire San Joaquin Valley of California, from Modesto in the North to Bakersfield in the South. The private contract for this project was awarded to Condor Earth Technologies in May of 2004. In addition to the extensive network observed by Condor, the California Department of Transportation has contributed 3 GPS subnetworks attached to the overall scope of the network - one project near Los Banos, another near Visalia, and an earthquake study in the vicinity of San Luis Obispo, which has been carried out to estimate the displacements resulting from the Paso Robles earthquake in late December of 2003. In addition to the GPS networks, Caltrans has run more than two hundred kilometers of precise leveling across the valley floor.

    The active geology of this survey includes not only the Paso Robles earthquake, but also vertical subsidence of more than a meter over a period of 12 years in the vicinity of Chowchilla. Because the observations used to construct this network have taken place over a period of more than a year, the project has been modeled as a multi-epoch network, with adjusted velocities and displacements being estimated for four different temporal epochs. The estimated time of completion of this project is the end of the year 2004. It offers substantial challenges in virtually every aspect of geodetic surveying in California, including adjusted geoid models, adjusted velocity models, earthquake models contributed by the Souther California Earthquake Center and adjusted by CSRC, and complex constraints tied directly into the CSRS networks of active IGS GPS sites. (Contributed by: Mike Potterfield)