3 arc-second SRTM terrain elevation data for the entire world (from approximately 60N to 54S latitude) is available in the unprocessed .HGT format by going to: http://dds.cr.usgs.gov/srtm/
We recommend using the version 2 data. More information about this data is available from: http://www2.jpl.nasa.gov/srtm/
The data is stored in files whose name represents the SW corner of a one degree area. The data can directly used in the EDX program by specifying the type and location of the data files using Databases -> Terrain. The files can also be converted to the EDX .201 format as well by doing the following:
- Open the EDXCV file conversion utility and do File -> New to initialize the program.
- Select Conversions -> Terrain File Conversion
- The “Source File” is the .HGT file. (example: “N45W123.HGT”)
- The “Destination File” is the name of the .201 file to be created. A recommend name would be the same as the source file except that the “HGT” replaced with “201”
- The “Conversion Type” is “SRTM 3 arcsecond HGT format to EDX 201 format”.
- Start the conversion.
Please be aware of the following notes as provided by the USGS:
“As with all digital geospatial data sets, users of SRTM must be aware of certain characteristics of the data set (resolution, accuracy, method of production and any resulting artifacts, etc.) in order to better judge its suitability for a specific application. A characteristic of SRTM that renders it unsuitable for one application may have no relevance as a limiting factor for its use in a different application.”
“The .HGT data should be considered as research grade suitable for scientific investigations and development and testing of various civil applications.”
“No editing has been performed on the data, and the elevation data in particular contain numerous voids and other spurious points such as anomalously high (spike) or low (well) values. Water bodies will generally not be well-defined – in fact since water surfaces generally produce very low radar backscatter they will appear quite noisy or rough, in the elevations data. Similarly, coastlines will not be well-defined.”