Estimation of Annual CO2 Emission from Coal Fires in Majiliang Mine, Datong, Northen China Using UAVs Thermal Infrared Remote Sensing Technology

Underground coal fires usually consume a large amount of coal resources and emit a variety of chemical compounds involving greenhouse gases. To estimate the annual CO ₂ emission from coal fires, a thermal infrared and a color imaging device amounting on Unmanned Aerial Vehicles (UAVs) are separately adopted to collect color and thermal infrared images over the coal fire areas in Majiliang Mine, Datong City, Northern China. First, standard blackbody is used to calibrate DN values of thermal imagery into the radiation values under the laboratory environment. Color and thermal infrared orthophotos are respectively generated by searching tie points and bundle adjustment processes, then Objects-oriented classification approach is used to classify land covers based on these high-resolution color imagery, subsequently land cover types associated ASTER spectral library are applied to estimate their emissivities. The atmospheric correction parameters are calculated by weather parameters (eg. Air temperature, humidity, barometric pressure) using MORTRAN software. In this case, atmospheric correction parameters and emissivities of land surface objects are inputted into the Radiative Transfer Equation (RTE) in order to retrieve the land surface temperature of mine area according to the thermal infrared orthomosaic. We use an adaptive edge threshold algorithm based on sobel operator to recognize coal fires. We measured tens of concentration of CO ₂ using a chamber over some fissures of mine surface, averaged them and investigated the number of fissures in situ, afterwards CO ₂ concentration is transformed into CO ₂ flux and the density of fissures are derived according to the areas of the surveyed region. The density of fissures is utilized to replace the emission coefficient of CO ₂ . Ultimately according to the carbon emission flux model, emission coefficient of CO ₂ , emission flux of CO ₂ and area of identified coal fires are combined to compute the total annual emission of CO ₂ (2366.02 t/y) in Ma Jiliang mine.