Radar and topography

Radar has also been used to create topographic data of the Earth’s surface. This is invaluable to archaeologists, whether for mapping or finding new sites, or for understanding the wider landscape.

_{The location of the Valley of the Kings, near Luxor, Egypt. Data courtesy of the USGS.}

Using satellites, radar can produce elevation data for the entire globe. Although multiple programs have created such a dataset, the first was NASA’s Shuttle Radar Topography Mission.

Shuttle Radar Topography Mission (SRTM)

The SRTM program utilised a SAR system mounted on NASA’s Space Shuttle Endeavour. It orbited the Earth 176 times over an 11-day mission in 2000, collecting data for 80% of the Earth’s surface.

_{Simulated image of the SRTM instrument collecting data onboard the Space Shuttle. Courtesy of NASA.}

The SAR system consisted of two separate antennae, one in the space shuttle and the second mounted on the end of a 60m mast. This provided two sets of data with the shuttle antenna transmitting and receiving the signal, and the second masted antenna just receiving the reflected signal. By combining both signals it was possible to work out the elevation of each area of the Earth’s surface.

The raw SAR data was processed by NASA to create a topographic dataset for the entire Earth. Over the years this has been reprocessed and improved, with a final dataset released in 2015 at 30m resolution. Only the very north and the very south of the globe are not covered.

_{SRTM data coverage. Data courtesy of the USGS and Natural Earth.}

The SRTM topographical data is free to download as a digital elevation model – we will learn more about this type of data in the next step!