Vertical Accuracy of Shuttle Radar Topography Mission (SRTM) & Advanced Spaceborne Thermal Emmision & Reflection Radiometer (ASTER) Data

Digital Elevation data produced by NASA’s Shuttle Radar Topography Mission (SRTM) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) are currently the most detailed publicly available, free-of-cost, near-global Digital Elevation Models (DEM). While generally very successful in collecting complete and accurate elevation data, the missions C-band radars had limitations over specific landscapes, including sand deserts, marsh lands and urban areas such as typically found in the Republic of Iraq. This paper presents the results of a validation study using data from ground surveys during the 3D seismic campaign in Iraq over differing terrain morphology. It tests a) the accuracy of finished Level 2 SRTM DEM data and ASTER 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 Errors (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 terrain with heights of more than 20 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 marsh or urban areas do not reproduce the representative topography of such a landscape and that spatially higher resolved elevation data is needed to achieve this via interpolation.