Interferometric Monitoring of an Active Underground Mining Field with High-resolution Sar Sensors

Underground mining activities lead to ground movements at the earth surface. An area-wide monitoring and the documentation of mining induced influences are required by the mining authorities. Work done in the past confirmed a significant potential of SAR interferometric methods to contribute information to such monitoring. Nevertheless, in spite of advanced SAR interferometric processing techniques and numerous convincing results, there are general limitations to the utility of the application. For the monitoring of mining induced deformation information gaps may occur, especially in the case of high deformation rates. Another common problem of SAR interferometry is the loss of coherence in rural areas. The new generation of SAR sensors shows a significant improvement of the applicability of interferometric techniques for mining related surface deformation. The higher spatial resolution of the TerraSAR-X sensor and its shorter repeat intervals lead to easier phase unwrapping with the possibility to measure high deformation rates. Alternatively, the use of the longer L-band wavelength of ALOS PALSAR offers good possibilities in rural areas and in the case of fast surface movements. The German hard coal mining company RAG Aktiengesellschaft (RAG), in cooperation with the Clausthal University of Technology and GAMMA Remote Sensing set up the R&D project “GeoMon” to investigate the potential of the available new SAR sensors for monitoring surface deformations above an active and an abandoned mine. The results of the interferometric analysis using TerraSAR-X and ALOS PALSAR data will be presented combined with the validation of the results with comprehensive terrestrial measurements. * Corresponding author. 1. INDRODUCTION The successful launches of the satellites ALOS (L-band) and TerraSAR-X (X-band) have made available high-resolution SAR images with high potential for ground motion monitoring. Previously, the use of C-band SAR sensors showed limitation for deformation monitoring in rural areas and in the case of high deformation rates and gradients. The higher spatial resolution of the TerraSAR-X sensor and its shorter repeat intervals lead to easier phase unwrapping with the possibility to measure high deformation rates. Alternatively, the use of the longer L-band wavelength of ALOS PALSAR offers good possibilities in rural areas and in the case of fast surface movements. Underground mining activities lead to ground motions at the earth surface. A regular area-wide monitoring and the documentation of mining influences are required in Germany by the mining authorities. Currently, there is a high interest in the mining sector in SAR interferometric techniques. But it is not clarified whether these techniques are able to contribute to the fulfilment of legal requirements by the mining industries as well as by the federal mining authorities. RAG started research projects to evaluate SAR interferometric techniques and the potential of the available new SAR sensors TerraSAR-X and ALOS PALSAR also in comparison to ENVISAT ASAR for monitoring surface deformations above an active and abandoned underground mine. For these purposes RAG developed a monitoring concept in cooperation with Clausthal University of Technology based on terrestrial measurements and simultaneous SAR sensor recordings. Furthermore, artificial corner reflectors were installed and insitu measurements were collected.