SRTM

Shuttle Radar Topography Mission (SRTM) was a United States NASA mission that used a C-band interferometric radar on the Space Shuttle Endeavour to measure the topography of Earth's land surfaces. The mission took place during STS-99 in February 2000 and aimed to produce high-resolution digital elevation models (DEMs) for scientific and practical applications.

During the 11-day flight, the radar system mapped about 80% of the Earth's land surface between latitudes 60°N and 56°S. The data collection resulted in a near-global DEM product set that has since become a foundational resource for geospatial analysis.

Data products include DEMs at about 30 meters (1 arc-second) resolution for most of the global coverage, along with a coarser 90-meter (3 arc-seconds) product for areas with sparser data. The mission also produced void areas due to radar geometry, which were subsequently filled in later processing to create continuous DEMs.

The data are released as free and openly accessible by NASA and the USGS, providing a widely used baseline for terrain analysis, hydrological modeling, cartography, and geospatial research. SRTM data support applications ranging from flood risk assessment and watershed analysis to landform studies and climate research.

Limitations include errors in forested and steep terrain, inaccuracies near water surfaces, and radar-specific distortions such as layover and shadow. Accuracy can degrade toward the edges of the swath, and polar regions are not mapped. Despite these limitations, SRTM remains one of the most influential sources of global elevation data.