Recent blog posts
New forum topics
According to the Canadian Centre for Topographic Information, a topographic map is a detailed and accurate graphic representation of cultural and natural features on the ground. In this web-site, I am using a narrower sense of the phrase to simply mean a map with contour lines to depict elevation.
There are two main sources of freely available elevation data that I am aware of and use:
Japan’s Ministry of Economy, Trade and industry (METI) and NASA released this on 29 June 2009. This GDEM (Global Digital Elevation Model) was created by stereo-correlating the 1.3 million scene ASTER VNIR archive, covering the Earth’s land surface between 83N and 83S latitudes from the year 2000 onwards. ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) is an imaging instrument flying on Terra, a satellite launched in December 1999 as part of NASA's Earth Observing System (EOS)
or Shuttle Radar Topography Mission. This space shuttle mission onboard the Endeavour collected topographic data over 11 days in February 2000 using a special dedicated instrument.
Note: The ASTER-GDEM has a finer horizontal accuracy but the data-set is less mature than the SRTM which has gone through several revisions where various fixes are applied to correct artifacts and errors. It also covers a time period which spans the year 2000 onwards, whereas the SRTM was taken on 11 days in February 2000.