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Vertical Accuracy of Shuttle Radar Topography Mission (SRTM) Elevation and Void-Filled Data in the Libyan Desert

Paul Elsner, Michael Bonnici


Elevation data produced by NASA’s Shuttle Radar Topography Mission (SRTM) is currently the most detailed publicly available, free-of-cost, near-global digital elevation model (DEM). While generally very successful in collecting complete and accurate elevation data, the mission C-band Radar had limitations over specific landscapes, including sand deserts. This paper presents the results of a validation study using data from ground surveys in the Libyan Sahara. It tests (a) the accuracy of finished Level 2 SRTM DEM data; and (b) the performance of an interpolation procedure that is routinely applied to fill SRTM data voids on a global scale. The results show that SRTM data consistently meets its own accuracy specifications, with a root mean square error (RMSE) of 1.3 to 5.2 m. Interpolated void-filled data achieved lower accuracy, with RMSE of approximately 7 m for an area of smaller dunes, and RMSE of 14 m within an extensive field of strongly undulating dunes with heights of more than 100 m, meaning that the accuracy specification of SRTM data in this area is not met. It is concluded that void-filling by interpolation in areas of extensive dune fields does not reproduce the representative topography of such a landscape, and spatially higher resolved elevation data is needed to achieve this via interpolation.

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