Altimetry is the measurement of the height above ground or above mean sea level of a geographical feature. These measurements can be profiled or mapped to form a digital elevation model (DEM), or a regular grid of elevation points over a specific area. DEMs provide valuable information about the Earth's land and sea surfaces and can be used for finding geographical features such as drainage basins, networks and channels, peaks and pits and other landforms, as well as for modelling hydrologic functions, energy flux and forest fires.

To make efficient use of altimetry data and other geospatial information in Canada, federal, provincial and territorial governments have undertaken the GeoBase initiative. This initiative ensures access to common, up-to-date and maintained quality geospatial data for all of Canada, including altimetry data.

To populate the Altimetry layer of this initiative the National Elevation Data project jointly produces Canadian Digital Elevation Data (CDED) with federal, provincial, and territorial governments. CDED consists of an ordered array of ground elevations at regularly spaced intervals. The source digital data for CDED is extracted from the hypsographic and hydrographic elements of the National Topographic Data Base (NTDB) at scales of 1:50 000 and 1:250 000, or from various scaled positional data acquired from the provinces and territories.

CDED serves as key primary data in a range of applications critical to support sustainable development. These applications include environmental and ecological impact assessments, water flow and water quality analysis, climate change studies, forest regeneration planning and wildlife habitats. Also, CDED can be used in the generation of three-dimensional graphics displaying terrain slope, profiles and line of sight. Non graphic applications include geoid calculations, terrain modelling, flood simulations and telecommunication studies.

GeoBase will become a critical source of consistent, national geospatial data to support natural resource management.

Project Priorities:

• Establish national standards for altimetry and product specifications for datasets in consultation with partners and stakeholders
• Establish partnership and maintenance agreements with GeoConnections and other federal and provincial partners
• Develop a prototype for the hydrographic network.
• Produce CDED datasets and digital elevation models (DEMs) in accordance with the national standard

For more information, please contact the project leader: Michel Cardinal

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