Background Maps
Map Types
Elevation
The elevation grid is derived from the US Geological Survey's (USGS) 1 x 1 km hydrologically corrected version of GTOPO30, a 30-arcsecond global digital elevation model assembled by the USGS. The Canadian portion of the data for GTOPO30 were obtained from two sources: Digital Chart of the World and Digital Terrain Elevation Data, both produced by the US National Imagery and Mapping Agency (formerly the Defense Mapping Agency).