R. Köthe1, M. Bock1,2
1 scilands GmbH, Goetheallee 11, D-37073 Göttingen, Germany
Telephone: +49 551 5315870
Fax: +49 551 5315873
2 University of Hamburg, Bundestraße 55, 20146 Hamburg, Germany
Telephone: +49 040 42838-7418
The application and availability of digital elevation models (DEM) and digital terrain models (DTM) is increasing since many years. Whereas in former years DTM were often derived from contour lines of topographic maps and stereoscopic measurements form aerial images nowadays small scale DEM are often derived form radar interferometry such as the well known DEM from the Shuttle Radar Topography Mission (SRTM) (http://www.jpl.nasa.gov/srtm/) which covers 80% of the earth’s landmass (Guth 2006). Large scale DTM are based increasingly on laser scanning which allows the interpolation of high resolution DTM with cell sizes < 1m.
However you can observe that the terms DEM and DTM are often used inaccurately. Another aspect is that for terrain analysis in geosciences often the DEM of other surfaces than the terrain (earth’s surface) is used. For example: using SRTM DEM in flat regions for calculating drainage basins will produce watersheds on forest canopies because SRTM DEM is (approximately) a DEM of the vegetation surface. This article aims – beside clarifying terms as DEM and DTM – on presenting approaches of preprocessing DEM/DTM to enable advanced terrain analysis in geoscience. The emphasis is on reducing elevation of forest canopies in radar based DEM (SRTM) and identifying and eliminating man-made terrain features in laser based DTM.