Geobase/Canadian Digital Elevation Data

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(from GeoBase)

The Canadian Digital Elevation Data (CDED) consists of an ordered array of ground elevations at regularly spaced intervals. The source digital data for CDED at scales of 1:50,000 and 1:250,000 is extracted from the hypsographic and hydrographic elements of the National Topographic Data Base (NTDB) or various scaled positional data acquired from the provinces and territories.

CDED files contain a Western and an Eastern section corresponding to half a National Topographic System (NTS) map sheet. Depending on the latitude of the CDED section, the grid spacing, based on geographic coordinates, vary in resolution from a minimum of 0.75 arc seconds to a maximum 3 arc seconds for the 1:50,000 NTS tiles, and from a minimum of 3 arc seconds to a maximum 12 arc seconds for the 1:250,000 NTS tiles respectively. Ground Elevations are recorded in metres relative to Mean Sea Level (MSL), based on the North American Datum 1983 (NAD83) horizontal reference datum.

CDED are used in geographic information systems (GIS) for land-management applications. CDED plays the same role as contours and relief shading on conventional paper maps but is 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.

Suitability to OSM

To date, mass elevation data has not been included in the main OSM database. The [cyclemap] adds elevation contours by rendering them from a separate elevation database taken from the [SRTM] data.

Import plan

Importing the Canadian elevation data would require a change of opinion from the community at large.

It is expected that the Canadian elevation data will be compared to the SRTM data as a data layer external to the OSM data base.

Those interested in the CDED should discuss it on the [CDED Talk Page] and on talk-ca.