The Global SRTM X-SAR DEM - Calibration, Validation, Production Status and Results

Abstract

In February 2000, the Shuttle Radar Topography Mission (SRTM) acquired a global digital elevation model (DEM) within only 11 days. Extensive testing and calibration activities primarily based on ocean surface data took place at DLR during the years 2000 and 2001. The calibration phase is now finished and the quality of the DEMs analyzed so far met all specifications. The routine processing of the SRTM X-band data at DLR started in November 2001. In June 2002, the generation of DEMs over Europe was completed and the data are available to the users. Furthermore, all interferograms covering Africa have been processed and parameters for the calibration have been systematically assessed. Now that thousands of image frames have been processed and mosaicked to DEMs, the large scale system stability becomes visible. Different height error contributions were investigated and our operational calibration was adapted accordingly. The calibration took place in several steps adjusting different parameters. Two examples from the initial calibration phase are shown in this paper. Afterwards, the calibration concept based on the use of ocean data will be presented and discussed as well as its operational implementation. The experiences from mosaicking based on self consistency will be reported. Finally, the overall SRTM X-SAR DEM production status and quality are presented.