LANDSAT-TM DATA FOR ESTIMATING GROUND TEMPERATURE AND DEPTH OF SUBSURFACE COAL FIRE IN THE JHARIA COALFIELD, INDIA

Coal fires are a ubiquitous problem in coal-mines, the world over. The y burn our prime energy resource, lead to atmospheric pollution and re nder mining of coal hazardous. Processes leading to coal combustion an d spread of subsurface fires are briefly examined in this paper and th e role of remote sensing in surveillance of coal fires is presented. T he present study aims at developing a quick method for estimating the temperature of the ground surface directly above subsurface coal fires . Utility of TM6 and TM7-band data for temperature estimation is brief ly reviewed. It is argued that temperature calculations of surface ano malies related to subsurface fires can only be done on the basis of 8- 14 mu m band data, due to the low temperatures involved. In the Jharia coalfield, it is noted that subsurface fires in various coal-mines ar e associated with surface thermal anomalies, as has also been confirme d by ground checks. The pattern of TM6 data distribution and ground tr uth is used to isolate thermal anomalies, and the TM6 digital numbers are converted into kinetic temperature values. It is observed that for the Landsat-TM scene (28 November 1990) the kinetic temperatures rang e from 16.0 degrees C to 31.6 degrees C in the Jharia coalfield, with a threshold value of 25.6 degrees C associated with the anomalies. Dep th estimation of fire has been carried out using field structural geol ogy data and pixel locations of thermal anomalies. It is inferred that the depth of subsurface coal fire ranges between 45-55 m, in most cas es, which is in general agreement with the field data. Limitations of the method are indicated.