prevention and control of spontaneous combustion - Mining and

The second case study is described in an extract from the actual report and shows the results of
research on environmental monitoring of spontaneous combustion in the North China
coalfields 44 .
Estimating the depth of subsurface coal fires was done with the help of field information on the
dip of strata. The depth of a subsurface fire can be computed using simple planar geometry.
The limitations arising from a number of factors are:
a) the rather coarse spatial resolution at 120m of the TM6 data
b) ignoring the atmospheric effects
c) non-uniform ground material
d) ignoring lateral variation in the spectral emissivity of the ground material
e) distances being measured in multiples of 30m, which means that depth estimates possess a
least count of (30 x tan 80)
f) fires at greater depth may be associated with a correspondingly poorer surface thermal
anomaly.
Case Study 2: Spontaneous combustion of North China coalfields.
The joint project, Detection, measurement and monitoring of spontaneous combustion of coal in
Northern China, was started in 1994 with the financial support of the European Community and
carried out by ITC. The main objectives are:
1) Investigating methods for the detection and location of coal fires
2) Developing methods of measuring coal fires
3) Developing methods of monitoring and prediction of coal fires by making use of remote
sensing data and GIS techniques.
In other words, by integrating remotely sensed data with other data (geological,
geomorphological, etc.), ways are being investigated to not only detect coal fires but also derive
the fire characteristics such as size, temperature, depth and direction of spreading direction from
the remotely sensed data.
After one years research, the following conclusions were drawn:
1) General image-processing techniques to extract coal fires from different remotely sensed
imagery can be developed. Thresholding can be used in night-time airborne thermal imagery
and night-time TM imagery. Principal components transformation is practical for daytime
airborne imagery and multiband combination for daytime TM imagery is an effective
approach to extracting information on coal fires and burnt rocks.
2) It is possible to establish links between remotely sensed information and actual ground
parameters through image measurement. The temperature and depth of a coal fire can be
calculated or estimated by using multiband TM imagery.
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