Shuttle Radar Topography Mission

Many regions on Earth are still poorly mapped due to persistent cloud cover or the inaccessibility of the terrain. The Mekong basin is no exception. Topographic information is a valuable commodity, and digital elevation data, such as recently provided by Shuttle Radar Topography Mission (SRTM), are in high demand for studying earthquakes or for mapping other hazards. However, elevation data can be used in many other ways.

The American SRTM instrument consisted of the Spaceborne Imaging Radar-C (SIR-C). Along with additional antennae, it was mounted on the Space Shuttle. The three-dimensional SRTM data are processed into individual tiles, each covering one degree by one degree in latitude and longitude. Sample spacing for individual data points is either 1 arc-second or 3 arc-seconds, referred to as SRTM-1 and SRTM-3, respectively. Since one arc-second at the equator corresponds to roughly 30 meters in horizontal extent, the sets are sometimes referred to as "30 meter" or "90 meter" data.

Compared to existing global DEM data, for example the frequently used GLOBE data set, the SRTM provides a new level of detail and consitency. The following example provides an illustration of both SRTM and GLOBE data for a mountainous area.

SRTM GLOBE

The SRTM mapped the continents between 60 degrees North and 56 degrees South latitude, which comprises almost 80% of the total landmass of Earth. This data set constitutes a near-global digital elevation model (DEM).

Global SRTM coverage acquired in 2002 by NASA/JPL

There has been very limited use of the SRTM data set for application in the Mekong Basin. So far, this very new and innovating topographic mapping technique has not been tested in this part of the world, and one has to rely on experimental results achieved in other areas. The following example is a colour shaded digital elevation model that has been derived by researches at the German Space Agency (DLR) from the SRTM 1 arc-second data set. Note that this example combines in a relatively small space of approximately 30 km by 30 km a variety of terrain features. These range from very rugged mountain ranges to hilly terrain and relatively flat terrain. The spatial resolution of this DEM is approximately 30 m.

 (SRTM data and map representation courtesy of NASA/JPL and DLR.)

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