INTERNATIONAL ARCHIVES OF PHOTOGRAMETRY AND REMOTE SENSING VOL. XXXII PART 7 PP. 555-558. APPLICABILITY OF ERS-1 AND ERS-2 INSAR FOR LAND SUBSIDENCE MONITORING IN THE SILESIAN COAL MINING REGION, POLAND. Zbigniew Perski ESA fellow in ESRIN, Frascati, ITALY and University of Silesia, Faculty of Earth Sciences, Department of Fundamental Geology, Bedzinska 60, 41-200 Sosnowiec, POLAND perski@us.edu.pl ISPRS Commission VII, Working Group 6 KEY WORDS: SAR, differential interferometry, mining, land subsidence, ABSTRACT In the study area in southern Poland some 130 Mio. tonnes of coal is extracted from 65 underground mines each year. As a consequence almost 6,000 sq. km of the Upper Silesian Coal basin is subjected to man inducted surface damages. The most dangerous factor is the land subsidence, causing damages to buildings and other constructions in a heavily populated area. The InSAR technique can be useful for monitoring the spatial distribution of mining subsidence and determine quantitative measuring for fixed time intervals. As an initial experiment, eight SAR images have been selected and five interferograms for 1 and 2 months periods in 1992 and in 1995 have been processed. For the topographic effects removal a DEM from the ERS-1 and ERS-2 tandem mission have been produced. Preliminary results are presented. On the interferograms from the 35-day periods in 1992 and 1993 subsidence effects have been identified, and a detailed interpretation and the comparison with ground data have been done. Initial interferometric tests show that InSAR technique can reveal spatial distribution of surface elevation changes due to mining activity. INTRODUCTION The Upper Silesian Coal Basin is located in south–central Poland. In this area the cities have an old mining tradition extracting since the Middle Ages silver, zinc and lead ore, and since the XIXth century coal . Due to this development the centre of Upper Silesia is very densely urbanised (4,000 citizens per 1 km 2 ), and heavily industrialised. 50 . 6 . 0 50 . 0 . 0 50 .12 . 0 50 .18 . 0 50 .24 . 0 50 .30 . 0 19 .10 . 0 1 9 .2 0 . 0 19 .30 . 0 19 .4 0 . 0 1 9 .1 0 . 0 19 .20 . 0 1 9 .3 0 . 0 19 .4 0 . 0 1 9 . 0 . 0 18 .50 . 0 19 . 0 . 0 18 .40 . 0 1 8 .5 0 . 0 18 .30 . 0 1 8 .4 0 . 0 18 .2 0 . 0 18 .30 . 0 49 .54 . 0 50 . 0. 0 1 8 .2 0 . 0 50 .18 . 0 50 .24 . 0 50 .30 . 0 50 . 6. 0 50 .12 . 0 5 0 1 0 2 0 3 0 4 0 k m 0 P O L A N D A Fig. 1: Location of the study area (black rectangle) on the bacground of the geological extent of the Upper Silesian Coal Basin and mining lease zones. The recent coal mines exploit 0.8 m to 8 m thick coal seams approx. 600 m under terrain surface. Each year these works cause 1m of the earth surface subsidence. However, development of depressions can be often much faster, reaching 1 to 3 cm per 24 hours. Such phenomena create huge hazards, especially for densely urbanised areas, what results damages to buildings and other constructions. Commonly subsidence is associated with sinkholing, deep fracturing of ground layer and changes in surface drainage pattern;. The problem of mining subsidence is as old as coal mining itself, but information on their extent is usually an unpopular item. Today, subsidence is calculated according to equation formulas: several empirical methods exists for prediction of the subsidence and for determination of the shape of depression (Kwiatek, 1997). The precision of the forecasting is controlled by geodetic surveying and shows ca 75% credibility of predictions. Such difference shows how complex are the natural conditions, especially for areas with multi-seam and multi-level coal extraction, espetially where old abandoned works are reactivated. The real extent of subsidence is never regularly surveyed on- site. The field measurements are done usually twice annually along selected traverses or around important engineering constructions (e.g. communication trails, factories, river banks). In the Upper Silesia no independent and spatially well distributed surveyor’s network exist. REPEAT-PASS RADAR INTERFEROMETRY Repeat-Pass Radar Interferometry has a high potential for the measurement of land subsidence and other surface changes. It is a relatively new method but results of tests and experiments demonstrated the capability of this technique to measure man- inducted surface movement to centimetre resolution; e.g.: Bonn Experiment (Timmen et al., 1996), Urban Subsidence Mapping (Haynes et al 1997), subsidence at oil and gas exploration sites (van der Kooij et al., 1995, van der Kooij, 1997). Application of SAR interferometry to study the impact of underground mining has been theoretically described by Carnec et al. (1994) and tested in Selby Coalfield in the UK (Stow, 1996, Stow & Wright, 1997).