CDGPS, a partnership between all provinces, Nunavut and the federal government, is a Canada-wide service that distributes NRCan's wide-area differential GPS corrections (GPS·C ) in real-time via MSAT communication satellite.

GPS·C is a real-time product of the Canadian Active Control System (CACS). It provides a national differential GPS standard that ensures spatial integrity.

CDGPS is one method of delivering GPS·C corrections to GPS users across Canada. The user requires a CDGPS radio which can be purchased through resellers for approximately $1500 (see the CDGPS website's dealers page).

• The CDGPS radio has an onboard low-grade GPS chip that enables it to output corrected positions in NMEA format directly (without the use of an additional GPS receiver). The accuracy of these NMEA positions is in the order of several metres only (mode not recommended).
• The unit can output corrections localized in RTCM format based on the location determined by the onboard GPS chip. When connected to a user's external GPS receiver, the CDGPS radio acts as a virtual base station.

REAL-TIME Distribution of GPS-C Corrections via CDGPS

• The unit can also output the GPS·C corrections in an RTCA-like format suitable for dual frequency GPS receivers. A prototype interface to a dual-frequency receiver is currently being developed under the Geomatics for Northern Development Program. The expected real-time horizontal accuracy will be in the order of decimeters.

The CDGPS project is managed by BC's Ministry of Sustainable Resource Management, Base Mapping and Geomatic Services.

GPS·C has an open broadcast protocol and provides distribution opportunities to value-added resellers and service providers wishing to propose additional distribution methods.

For more information about this activity, please contact: