Using Ers Sar Interferometry for Dem Creation in the Czech Republic

This paper summarises first results of the study carrying out in the frame of the programme for co-operation between European Space Agency and Czech Republic. One part of the study concentrates on the evaluation and development of the application potential of the SAR interferometry technique for DEM generation in the Czech Republic. The only DEM currently available for the entire country is the 100 m grid elevation model based on the topographic maps. ERS interferometry could represent very effective method for generation of more detailed and more accurate DEM. ERS1/2 tandem data acquired in March 1997 were used at the beginning of the study. The interferometric pair with the baseline of 106 m was processed in two main steps: SLC data generation and interferometry analysis. Generation of SLC data using the SAR processor developed together with the software for SAR interferometry processing is the preferred method that assures smooth import and analysis of input data. The complete procedure including SLC data coregistration, interferogram generation and enhancement, phase unwrapping and DEM generation was then applied. All individual processing steps were analysed and some eligible functions were used to improve the quality of the resulted DEM (slope mapping, Gaussian weighting, ...). The dense grid of elevation points digitised from 1:50 000 topographic maps (1200 points describing all main terrain features in the overlap area) was prepared for evaluation of resulted interferometric DEM. The final DEM is featured by the elevation RMS error of 13 m. The RADARSAT stereo pair (S3,S7) was available for the same area. The elevation RMS error of the DEM, generated using this technique, was 25 m. Forthcoming planned activities will cover other topics such as generation of interferometric DEM with the use of existing external DEM, combination of descending and ascending ERS interferometric pairs or analysis of several interferometric pairs with different baselines.