Global Elevation Datasets

There are numerous elevation datasets with global or nearly global coverage, but by far the most significant is SRTM.

SRTM: NASA Shuttle Radar Topography Mission

ASTER Global Digital Elevation Map (GDEM)

• GDEM is 30m elevation dataset created by stereo-correlating the 1.3 million scene ASTER VNIR archive, covering the Earth’s land surface between 83N and 83S latitudes, formatted in 1 x 1 degree tiles as GeoTIFF files.
• It's supposedly available from NASA’s EOS data archive ("WIST") however, the process is cumbersome, involving registration and a complex search.
• In fact, as of July 2009, when i attempted to find GDEM for two areas (Hawaii and Bolivia), both searches came back with the name of the data file (e.g. ASTGTM_S20W065.zip) but "On-line Access: Access Unavailable"
• In a review at the time of release, it was observed that "While the elevation postings are ~30 m, the detail of topographic expression resolvable in the ASTER GDEM appears to be between 100 m and 120 m... residual cloud anomalies, a variety of pervasive artifacts.. straight lines, pits, bumps, mole runs, and other geometric shapes.. unsightly bump/pit pairs."

GTOPO30

• Global 30 Arc Second Elevation Data Set, distributed by the USGS
• same resolution as DTED0, GLOBE and SRTM30 - but older and less accurate
• a collection of 33 files, grid spacing of approximately 1 km
• the file extension is "DEM" but it's not the same format as normal USGS DEM
• USGS HYDRO 1K Elevation Derivative Database is a version of GTOPO30 which has been corrected using hydrology data
• For an amazing experience browsing (but not downloading) GTOPO30, try ER Mapper's EarthEtc Imagery server, in particular their EarthStar World DEM dataset

NOAA GLOBE Project

• like GTOPO30, another 30 Arc Second dataset (~ 1 km)
• it is newer or more accurate than GTOPO30 in some areas
• the data is not in any format at all - just large blocks of raw binary 16-bit values, with headers in a separate file
• has a number of nicely pre-rendered versions of the dataset
• has a handy form, GLOBE: Select Your Own Area to specify and download a rectangular area (in geographic coordinates)

Other Global Elevation

• LandInfo - Maps and International GIS Map Products
  • largest vendor of international map products
  • costs can be high; e.g. $600 per 1-degree quad
• individual countries - see the Locations Page
• Converting from contour maps may be necessary if DEMs are not available for your area of interest