11 November 2010
A digital elevation model (DEM) is a digital representation of ground surface topography or terrain.
There exists a lot of different file formats for storing DEM data. The GDAL (Geospatial Data Abstraction Library) allows to read, write, convert and extract data from several DEM file types
For Spain, there is the CNIG (Centro Nacional De Información Geográfica - España) from where DEM maps with 30m resolution can be downloaded for free. This files are in Arc/Info ASCII Grid format.
Using the GDAL python bindings all this data can be read into a python program using numpy arrays for efficiency.
Sources and databases with available DEM
- USGS/EROS
- Earth Resources Observation and Science (EROS) Center. DEMs for USA The National Elevation Dataset (NED), Shuttle Radar Topography Mission (SRTM, 90m for world and 30m for US), DEM elevation values that have been primarily derived from the USGS topographic map series, Global 30 Arc-Second Elevation Dataset (GTOPO30).
- CNIG - Centro Nacional De Información Geográfica - Spain.
- MDT25 (25 m/pixel), MDT200 (200 m/pixel) The MDT25 files are *.agr (ESRI ArcInfo ASCII Grid).
- View Cartographic
- Has downloadable DEMs for all the world (paying). For Spain it has 90m DEMs (SRTM3 from NGA) and 90m cartographic scanned DEM (very expensive).
- NASA World Wind
- World Wind is an open source (released under the NOSA license) virtual globe developed by NASA and the open source community. It is a Java application and so it is cross-platform.
More reference lists
- FreeGIS.org
- The freegis.org site has a list of data sources of DEMs in the Geo-Data section
- Digital Terrain Modeling and Mapping
- Other list of DEM sources more complete than this.
- MapCruzin
- Free GIS Shapefiles, Software, Resources and Geography Maps. It has an entry with resources for terrain maps
Related tags: gis