SRTM

STM is an acronym for Shuttle Radar Topography Mission, which is an international effort that obtained digital elevation models on a near global scale on the globe from 56 degrees South to 60 degrees North. STRM consisted of a Radar System which flew on the Endeavour space shuttle. during the STS-99 mission in February 2000.

Elevation models

Elevation models derived from the STRM data can be downloaded freely from the internet. Their file extension is .hgt and they can be downloaded freely from the internet. SRTM Files can be extracted at http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp.

ESRI ASC raster format

Rather than being able to parse binary .hgt files, the Field 3D manager is able to read the data in ESRI ASCII interchange format.

The ASCII .asc file has the following file format:

• ncols: number of columns in the tile
• nrows: number of rows in the tile
• xllcorner: the longitude Left Down Corner of the tile
• yllcorner: the latitude Left Down Corner of the tile
• cellsize: the size of latitude / longitude of each cell in the tile
• NODATA_value: the value which will be used in the datas below for a cell which has no valid data
• The list of datas for each cell in the grid

There will be ncols * nrows cells, each cell having cellsize dimension in latitude onad longitude

Example

      ncols         6001
      nrows         6001
      xllcorner     -0.8
      yllcorner     -2.6
      cellsize      0.00083333333333333
      NODATA_value  -9999
      436 437 439 440 441 439 437...

Usage in 3D Maps

SRTM Files must be used in ASCII .asc raster format. Zip Files can directly be used without having to extract them.