NRCan's Canadian Geodetic Service (CGS) maintains the Canadian Spatial Reference System (CSRS) as a national standard for geospatial and Earth sciences information. The associated frame of reference for latitude, longitude, height and gravity serves as the foundation for coordinate-based information systems and our nation's georeferencing and related geoscience needs. This in turn enables the seamless integration and interoperability of applications and data with a spatial component, including those implicated in a wide range of activities from land surveys to mineral exploration; from navigation and mapping to the use of remote sensing data for resource management; and from the construction of dams and pipelines to the interpretation of seismic disturbances.

GPS is the common tool of choice for users to easily access the CSRS. The GPS-based products and services outlined below not only contribute to provide the means to enhance nominal accuracy of GPS but ensure that the derived coordinates are consistent with the national reference system.

The Canadian Geodetic Service maintains the Canadian Active Control System (CACS), the infrastructure that permits the realization of the CSRS as well as access to it. The CACS is a cross-Canada network of Active Control Points (ACP). Each ACP includes a high-quality dual frequency receiver that continuously records GPS raw observational data.

Canadian Active Control Network Configuration

Permanent CACS tracking sites operated by CGS (10 stations)
Regional Active Control Sites operated by CGS (19 stations)
Western Canada Deformation array operated by GSC (13 stations)

At the Ottawa central control site, the GPS raw observational data is collected, archived and shared with the International GPS Service (IGS). From this data, precise orbit and satellite clock corrections are computed and made available.

CACS data is also the source of two new GPS correction services that provide GPS users with greater positioning accuracies:

1. CDGPS Canada-wide DGPS correction service (REAL-TIME)
2. CSRS-PPP Precise Point Positioning service (POST PROCESSING)

These new services are particularly useful in the Canadian North which lacks an abundance of recent geodetic control monuments. The Geomatics for Northern Development Program supports these services through:

• Consultation with Northern GPS users and promoting the new services
• Creation of a practical user guide "GPS Positioning in Canada - Considerations for Getting the Accuracy You Want Where You Want It and When You Want It" to help GPS users, including non-experts, understand their GPS positioning and integration options (in terms of equipment, technique and accuracy)

For more information about this activity, please contact: