CDED

The Canadian Digital Elevation Data (CDED) consists of an ordered array of ground elevations at regularly spaced intervals. These CDED are based on National Topographic System (NTS) maps at the scale of 1:250 000. Other complementary sources include elevation data, aerotriangulation control points, and geodetic control points.

The coverage of every file corresponds to half an NTS map sheet, which means that there are western and eastern parts to the CDED for every NTS map at the 1:250 000 scale when necessary. The grid spacing is based on geographic coordinates at a maximum resolution of 3 arc seconds and a minimum resolution of 12 arc seconds depending on latitude. It consists of elevation data recorded in meters relative to mean sea level based on the NAD83 horizontal reference datum.

Quality control is implemented throughout the production process. These CDED are produced jointly by the Centre for Topographical Information (CTI) and the Canadian Forest Service, Ontario Region (CFS). All CDED files are produced using ANUDEM (Australian National University Digital Elevation Models) software.

CDED have assumed a major role in digital mapping. They are used in geographic information systems (GIS) for land-management applications. CDED play the same roles that contours and relief shading do on conventional paper maps, but are more powerful analytically. In addition to providing estimated values of elevation points, CDED can be used to determine orientation and the slope of each point when used in GIS applications. CDED can also be used for terrain modeling, for calculating the influence of the terrain on line-of-sight, for radar imaging, for simulating flooding, and similar applications.