Further information can be seen at this link:


SDCRTN photoDescription: The San Diego County Real Time Network (SDCRTN) is a high-precision positioning service provided by the County at no cost to the user. There are 19 continuously operating reference stations (CORS) distributed through out the County. These CORS are a part of the California Spatial Reference System (CSRC) and the California Real Time Network (CRTN) and contain dual-frequency GPS receivers and geodetic antennas equipped with choke rings and radomes. The CORS collect GPS measurements at a rate of 1 Hz or better and relay the data via either the San Diego County RCS or the HPWREN microwave network to a server located at the University of Southern California (UCSD). The raw measurement data from each CORS is repackaged into RTCM message types 18, 19, 3, and 22 and assigned to a port specific to that CORS. The user can access the data via TCP/IP using a wireless data modem. Latency is typically on the order of 1 second.

The server also processes the CORS data in real time to check the data quality and to analyze the network integrity. Data is stored at 1 Hz for post-processing. See  Data Archive at SOPAC

Using the SDCRTN:  To utilize this service, a Code Division Multiple Access (CDMA) data modem is required to provide the communication link between the SDCRTN server and the user’s GPS receiver.

See Procedures for using the SDCRTN

See How the SDCRTN was constructed

Contact:  Email SDCRTN


San Diego County provides the SDCRTN as a service to the general surveying community. The County makes no expressed warranty or guaranty as to the accuracies of the resultant coordinate values or their use. Use of the SDCRTN should only be attempted by experienced professionals, licensed to practice land surveying in the State of California.

The County makes no expressed warranty or guaranty that on any given day the network or any part thereof will be up and running. The County will however, endeavor to post the current day status of the system or future planned service outages on our webpage.

The County is not responsible for the configuration of the different types of equipment utilized by the private sector professional in connection with the use of the SDCRTN. If you have specific questions, please direct them to your equipment supplier/representative.

San Diego County supports the California Real Time Network.