USGS EROS Archive - Digital Elevation - SRTM Mission Summary

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What is SRTM?

The Shuttle Radar Topography Mission (SRTM) is a joint project between the National Geospatial-Intelligence Agency (NGA) and the National Aeronautics and Space Administration (NASA).  The objective of this project is to produce digital topographic data for 80% of the Earth's land surface (all land areas between 60º north and 56° south latitude), with data points located every 1-arc-second (approximately 30 meters) on a latitude/longitude grid.  The absolute vertical accuracy of the elevation data will be 16 meters (at 90% confidence). This radar system will gather data that will result in the most accurate and complete topographic map of the Earth's surface that has ever been assembled.

What can the data be used for?

These data can be tailored to meet the needs of the military, civil, and scientific user communities. But other uses of this data include improved water drainage modeling, more realistic flight simulators, better locations for cell phone towers, navigation safety, and even improved maps for backpackers.

Just about any project that requires accurate knowledge of the shape and height of the land can benefit from this data. Some examples are flood control, soil conservation, reforestation, volcano monitoring, earthquake research, and glacier movement monitoring.

How it was done?

SRTM made use of a technique called radar interferometry. In radar interferometry, two radar images are taken from slightly different locations. Differences between these images allow for the calculation of surface elevation, or change. (If you'd like a more detailed explanation of interferometry, please check out our Data: Interferometry section.) To get two radar images taken from different locations the SRTM hardware consisted of one radar antenna in the shuttle payload bay and a second radar antenna attached to the end of a mast extended 60 meters (195 feet) out from the shuttle.

What part of the Earth was be mapped?

SRTM was launched in an orbit with an inclination of 57 degrees. This allowed all of the Earth's land surface that lies between 60 degrees north and 56 degrees south latitude to be covered by the SRTM. This is about 80 percent of the Earth's land mass. See coverage maps.

Access Data

EarthExplorer can be used to search, preview, and download Shuttle Radar Topography Mission (SRTM) 1 Arc-Second Global data. The collections are located under the Digital Elevation category.