Shuttle Radar Topography Mission

The Shuttle Radar Topography Mission (SRTM) is an international research effort that obtained digital elevation models on a near-global scale from 56°S to 60°N, to generate the most complete high-resolution digital topographic database of Earth prior to the release of the ASTER GDEM in 2009. The technique employed for generating topographic data by radar is known as interferometric synthetic aperture radar.

Source: Wikipedia — Shuttle Radar Topography Mission (CC BY-SA 4.0)