San Diego County Real Time Network

Real Time Network equipment outdoors

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 and are a part of

California Spatial Reference System (CSRC) and

California Real Time Network (CRTN)

CORS contain dual-frequency GPS receivers and geodetic antennas equipped with choke rings and radomes. CORS collect GPS measurements at a rate of 1 Hz or better and relay the data via either 

San Diego County Regional Communications System (RCS) or

High Performance Wireless Research and Education Network (HPWREN) at 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 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.

Data Archive at SOPAC

Procedures for using 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.

How SDCRTN was constructed

Contact SDCRTN


The County of San Diego 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.

The County of San Diego supports the California Real Time Network