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| Shuttle Radar Topography Mission (SRTM) mosaics |
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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.
Background
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.
If you have questions, please do not hesitate to
contact us.
Additional SRTM sources:
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