NASA Shuttle Radar Topography Mission United States 1 arc second

SRTM was a primary component of the payload on the Space Shuttle Endeavour during its STS-99 mission. Endeavour launched February 11, 2000, and flew for 11 days. Each SRTMUS1 data tile contains a mosaic and blending of elevations generated by averaging all "data takes" that fall within that tile.

These elevation files use the extension “.HGT”, meaning height (such as N37W105.SRTMUS1.HGT). The primary goal of creating the Version 3 data was to eliminate voids that were present in earlier versions of SRTM data. In areas with limited data, existing topographical data were used to supplement the SRTM data to fill the voids.

The source of each elevation pixel is identified in the corresponding SRTMUS1N product (such as N37W105.SRTMUS1N.NUM). SRTM collected data in swaths, which extend from ~30 degrees off-nadir to ~58 degrees off-nadir from an altitude of 233 kilometers (km). These swaths are ~225 km wide and consisted of all land between 60 degrees N and 56 degrees S latitude.

This accounts for about 80% of Earth’s total landmass.

Known Issues

* Known issues in the NASA SRTM are described in the following publication: Rodriguez, E., C. S. Morris, and J. E. Belz (2006), A global assessment of the SRTM performance, Photogramm. Eng. Remote Sens., 72, 249–260. doi.org/10.14358/PERS.72.3.249