A physical method to analyse scattered waves from burnt coal seam and its application to estimate thickness of fire scars in central Borneo using L-Band SAR data

摘要

A physical method was conducted to analyse scattered waves from burnt coal seam in order to estimate the thickness of fire scars. The model was composed of three media namely; air, burnt coal seam and peat. For computation purposes, the equivalent circuit of this model was conducted using a classical transmission line circuit method. The relationship between backscattering coefficient and thickness of burnt coal seam was defined in terms of the logarithm of the reflection coefficient (in power). The analysis result was confirmed by simulation using a Finite Difference Time Domain (FDTD) method. The simulation was performed using a two-dimensional (2-D) finite-difference model for scattered waves from a burnt coal seam. The model used the equations of scattered electromagnetic fields that were derived from Maxwell's equations. A Mur method was used to surround the simulation space and absorb the outward travelling waves. Analysis and simulation results were similar. Subsequently, the model was applied to estimate the thickness of burnt coal seam in central Borneo fire events, that occurred in 1997, using a Japanese Earth Resources Satellite (JERS-1) SAR data. Results showed that fire scars in the study area reached 0.52m in depth (thickness). This agrees with ground measurements.