On This Page:

• Overview
• Sample Area and Images
• CDED1 1:50,000
• CDED1 1:250,000
• SRTM 3 arc-second
• SRTM 30 arc-second
• GTOPO 30 arc-second
• DTED0 30 arc-second
• GLOBE 30 arc-second

At This Site:

• About
• Software
  • DRGMapCal
  • CANgrid
  • OziExplorer Info
  • OziExplorer Utilities
• Maps
  • Map Comparisons
  • DEM Comparisons
  • Canada Landsat-7 images
• GPS
  • Buying a GPS receiver
  • GPS reception in trees
• Degree Confluence Project
• Xterra
• Photos
• Donations

The goal of this page is to provide some comparisons of the use of free Digital Elevation Model(DEM) data from various sources. In order to make it easier to compare the different DEM data, the same geographic area is used for each example.

Examples are listed in decreasing order of DEM resolution. DEM resolution is usually specified in "arc seconds", which means the number of seconds of latitude or longitude. The actual distance covered by an arc-second varies for different parts of the world, but a guideline is:

• 1 arc second = 30 meters
• 3 arc seconds = 90 meters
• 30 arc seconds = 1 kilometer

Roughly speaking you can consider that a DEM has an elevation value for each 'grid square' for the area covered by the DEM. For a DEM with a resolution of 1 arc-second, this means having an elevation value for each 30x30 meter portion of the coverage area. For a 30 arc-second DEM, there would be one elevation value for each square kilometer.

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All the sample images are from screen captures while the DEMs were being used in OziExplorer 3D. The OziExplorer website(and the OziExplorer Help File) lists sources of DEM data. The map image is part of the Spectrum Digital Imaging 092G06 1:50,000 scale topographic map image. The wireframe versions of the map image are shown because they help illustrate how the DEM represents the earth's surface. The images displayed on this page link to "full sized" PNG images. The area used for the samples is centered on 49°22'30"N 123°15'00"W, which is the center of the Canadian National Topographic System 1:50,000 scale mapsheet 092G06 (North Vancouver), and this is the same area used in the images on my Map Comparisons page.

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Map image using the 0.75 arc-second GeoBase Canadian Digital Elevation Data Level 1 DEM at 1:50,000 scale.

Wireframe image using the 0.75 arc-second GeoBase Canadian Digital Elevation Data Level 1 DEM at 1:50,000 scale.

Part of a satellite image from the GeoGratis Landsat-7 Orthorectified Imagery over Canada, using the 0.75 arc-second GeoBase Canadian Digital Elevation Data Level 1 DEM at 1:50,000 scale.

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Map image using the 3 arc-second GeoBase Canadian Digital Elevation Data Level 1 DEM at 1:250,000 scale.

Wireframe image using the 3 arc-second GeoBase Canadian Digital Elevation Data Level 1 DEM at 1:250,000 scale.

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Map image using the 3 arc-second SRTM (Shuttle Radar Topography Mission) North American data.

Wireframe image using the 3 arc-second SRTM (Shuttle Radar Topography Mission) North American data.

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Map image using the SRTM 30 arc-second data, which is a "near-global digital elevation model (DEM) comprising a combination of data from the Shuttle Radar Topography Mission, flown in February, 2000 and the the U.S. Geological Survey's GTOPO30 data set".

Wireframe image using the SRTM 30 arc-second data, which is a "near-global digital elevation model (DEM) comprising a combination of data from the Shuttle Radar Topography Mission, flown in February, 2000 and the the U.S. Geological Survey's GTOPO30 data set".

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Map image using the 30 arc-second GTOPO30 data.

Wireframe image using the 30 arc-second GTOPO30 data.

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Map image using the NIMA(now called NGA) 30 arc-second DTED Level 0 data.

Wireframe image using the NIMA(now called NGA) 30 arc-second DTED Level 0 data.

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Map image using the GLOBE 30 arc-second data.

Wireframe image using the GLOBE 30 arc-second data.