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last update: October 4, 2013 9:48 AM
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Land cover
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Shuttle Radar Topography Mission (SRTM) mosaics
Through its outreach activities programme, GLCN promotes the distribution of base elevation data to workshop participants. Regional coverage of Shuttle Radar Topography Mission (SRTM) data is distributed using DVDs (cover sample on the right).

The availability of such digital elevation model is a great support for a variety of activities such as agricultural trends analysis, landcover changes studies (agricultural, urban, deforestation, land degradation) and the concomitant loss of natural ecosystems, holistic and integrated approach to the conservation and sustainable use of land resources, etc.

Interferometer Synthetic Aperture Radar (IFSAR) data were collected by the USGS during the Shuttle Radar Topography Mission over 80 % of the landmass of the Earth between 60 degrees North and 56 degrees South latitudes. The mission generated the most complete high-resolution digital topographic database of Earth.
USGS has made available SRTM data at three resolutions:
  • 1 arc-second (about 30 m) DEM of the United States
  • 3 arc-second (about 90 m) DEM of the world
  • 30 arc-second SRTM-GTOPO30 product (about 1 km) corrected by GTOPO30 30 arc-second DEM.
The USGS release of SRTM data has several speckling problems especially in associating with water and coastlines, which appears like noise in the data. Also, voids (lack of elevation data) caused by bad radar scatter are frequently present in the raw tiles especially in high mountains areas.

Techniques for processing holes and voids can be applied to improve terrain perception. FAO's Land Cover Topic Centre has applied a set of procedures to generate a seemless, mosaicked, void-free data set to be packed and distributed during the workshops. For more information on data and processes applied by FAO, please read the documentation.

Data Format
GLCN offers SRTM data in two formats:
  • ARC/INFO GRID (signed 16 bit)
  • GeoTIFF (signed 16 bit)
The format depends upon the original data source and collection process. Most GIS packages offer conversion tools that allow you to change data format easily.

Georeference Information
SRTM data is distributed in 20x10 degree tiles referenced to the Geographic Coordinate system.
srtm index
If you have questions, please do not hesitate to contact us.

Additional SRTM sources:

Food and Agriculture Organizations of UN United Nations Environment Programme Istituto Agronomico Oltremare (IAO) Italian Cooperation
For questions or comments, contact us  -  last update: October 4, 2013 9:48 AM