621 Geoinformation for European-wide Integration, Benes (ed.) © 2003 Millpress, Rotterdam, ISBN 90-77017-71-2 The integration of optical and InSAR data for land subsidence monitoring and its impact on environment of the Upper Silesian Coal Basin M. Mroz Department of Photogrammetry and Remote Sensing, University of Warmia and Mazury, Olsztyn, Poland Z. Perski Department of Geological Mapping, University of Silesia, Sosnowiec, Poland Keywords: InSAR, land subsidence, data fusion, environment ABSTRACT: It was demonstrated in many articles that interferometric satellite data (InSAR) from ERS-1/2 SAR sensor give the products from which a Digital Terrain Model can be extracted. A three-pass interferome- try (DiffSAR) is a strong and crucial remote sensing technique to monitor of terrain movements like land sub- sidence. The practical results of InSAR technique application for land subsidence monitoring for the Upper Silesian Coal Basin, a densely urbanised, heavily industrialised area were demonstrated in many papers of second author. Mining subsidence causes damage to buildings and other structures, changes surface drainage patterns and can be associated to deep fracturing of the ground. Knowledge of the spatial distribution of the endangered area may help in landuse planning and compensation strategies. The main aim of the work pre- sented in the paper was to demonstrate the synergism of optical and SAR data for environmental monitoring, precisely for land subsidence monitoring caused by coal mining activity and its impact on environment. The space maps in the form of color compositions were elaborated based on Landsat 5 optical data. To monitor the impact of coal mining activity on environment the maps showing land movements (subsidence) were elaborated from ERS SAR SLC data using Atlantis InSAR Workstation. Next, two remote sensing technolo- gies (interferogram and multitemporal composition from ERS also with multispectral compositions from Landsat) were fused for improvement of the interpretation of land cover in the regions of subsidence. This kind of multisource spacemaps can be useful not only for environmental monitoring "ex post" but also for fu- ture urban and regional planning purposes. 1 INTRODUCTION Since the 19th century the Upper Silesian Coal Ba- sin in Poland is one of the world’s biggest mining centres producing today some 130 million tonnes of coal from 65 underground mines each year. The negative aspect of such a magnitude of exploitation is visible on the surface in form of surface deforma- tion and subsidence. In this case an area of almost 1500 km 2 is affected (fig. 1). Changes in topography and hydrography damage buildings and other struc- tures in a substantial way. Furthermore, some of the affected areas had to be excluded from urbanisation planning. Nevertheless since 1970 almost 40% of coal mining activity are located under cities and im- portant infrastructures, i.e. in densely urbanised area, of 4000 inhabitants per square km. The effects of mining damages at the surface and the impact on the environment are not sufficiently mapped. Newest developments in remote sensing techniques (InSAR) may now allow mapping and prediction of mine damages more cost-efficient, more accurate and more frequent. The information about the subsidence extracted from interferometry only is not easily readable in the context of spatial localisation and surrounding of damaged terrain without a carto- graphic support lake maps or satellite images. 2 SUBSIDENCE MEASUREMENTS BY SAR INTERFEROMETRY 2.1 Subsidence due to mining The area under investigation covers approxi- mately 300 km 2 (fig. 2) and is affected by heavy mining activities with the exploitation of almost horizontal coal seams and subsequently filling, ap- plying hydraulic technology. Expected subsidence due to roof falling is 70 to 80% in volume of the coal seam thickness, and in case of hydraulic filling is reduced to 15 to 20%. But in any case, a subsi- dence trough develops (fig. 3). Initial downwarping is slow, not exceeding a few millimetres daily, after 6-8 months it accelerates to 1 cm per day. After the