Having a complete topographic coverage of Northern Canada is essential to establish a base for sustainable resource development. As things currently stand, the unmapped areas of the Canadian North would cover approximately 1 500 topographic sheets at the 1:50 000 scale, which represents about 80 sheets in the Northwest Territories and 1 400 in Nunavut.

As traditional mapping methods are expensive and hardly applicable to this part of Canada, new methods must be developed to produce topographic data.

The acquisition of topographic base data is twofold: planimetry which describes earth features and altimetry which describes the earths' relief. These two types of information are essential for a comprehensive description of the land. Once acquired, these information feed the geospatial data base which contains the base topographic information for the Canadian landmass.

In December 2002, mapping contracts, including the production of Digital Elevation Models (DEM), were carried out with RADARSAT and Landsat7 data. Given the promising outcome of the test phase, the Geomatics for Northern Development Program, in collaboration with the Canadian Space Agency, completed the tests in detail.

Contracts were awarded in the fall of 2003 to produce several topographic data sets at the 1:50 000 scale. These contracts used new methods with ERS, RADARSAT and Landsat7 satellite imagery. They also included the conventional stereodigitizing of aerial photography for data validation purposes.

Considering that:

• The required accuracy and content must meet topographic data at the scale of 1: 50 000;
• The production mode must rely on the best quality/cost ratio;

The tests outlined the following results:

• Extracting the hydrographic network requires a detailed data source such as aerial photography;
• RADARSAT 1 data source does not meet our standards;
• Planimetric data acquisition, presently can only be done with aerial photography combined with Landsat7 imagery for updating purposes;
• Altimetric data acquisition in the form of Digital Elevation Models (DEM) can be obtained by interferometry with ERS data in low and moderate terrain, and with aerial photography in mountainous terrain.

This approach was chosen by the Geomatics for Northern Development Program group in consultation with the major stakeholders. This approach will use aerial photography as source for planimetric data and the GeoBase Landsat 7 orthoimage for updating. DEMs are produced from ERS radar data or aerial photography depending on the type of terrain.

All of the data produced will be comparable to existing digital topographic data for Canada and will be available to users in the same manner as with the present data.

Implementation of the production system began in autumn of 2004 and had a target of 150 data sets per year. Production began in 2005 for altimetric and planimetric data acquisition.The first areas to be produced were chosen according to priorities set by the major stakeholders in Nunavut. Priorities are revised on a yearly base in order to adjust to changing needs. The following Figure illustrates completed and planned areas for the upcoming year.

Production status

Production status larger image [GIF, 203.4 kb, 708 X 916, notice]

For more information about this activity, please contact: Yves Robitaille