The Shuttle Radar Topography Mission (SRTM) was a collaborative effort between the National Aeronautics and Space Administration (NASA), the National Geospatial-Intelligence Agency (NGA), and the German and Italian space agencies, to generate a near-global digital elevation model (DEM). The mission homepage is at the NASA website, but the data are publicly distributed by the USGS EROS Data Center.
Digital elevation data consists of an ordered array of ground elevations sampled at regular intervals over each grid area. Aside from estimating point elevations, digital elevation has a variety of applications, including terrain modeling, line of sight analysis, water flow and flooding analysis, and many others.
1 arc second: The most recent version of the SRTM data has a resolution of 1 arc second, which is about 30m x 30m. The coverage is considered near-global, which means approximately 80% of the Earth's landmass is captured.
3 arc second: For this dataset, 3 arc second refers to the pixel size, which is roughly 90m x 90m. Each tile has a size of 1201 x 1201 pixels, covering roughly 36km x 36km (e.g. the local tile covers the core area of the Golden Horseshoe). The files are provided in .bil format, which can be immediately displayed in ArcMap.
30 arc second: A 30 arc second grid roughly translates to a pixel size of 1km x 1km. These tiles are much larger than the 3 arc second tiles both in coverage and in pixel number. For example, the "local" tile is 4800 x 6000 pixels in size, covering all of Ontario and Quebec, some of Manitoba and Nunavut, and with North-South coverage from the northeastern United States up to Greenland. The files are provided in .dem format, which can be immediately displayed in ArcMap.
SRTM data is available through the Library or by download through NASA's Earthdata Search tool.
