The research team, led by Chang'an University's Xiaoyuan He and Xingke Yang, flew an autonomous drone equipped with GPS and both visual cameras and High-resolution thermal cameras over Huojitu coal mine (HCM) in Shaanxi Province.
The team used the airborne thermal infrared (TIR) data generated by three drone flights at an altitude of 300m in combination with temperature measurements and image data that showed which surface fissures were emitting smoke.
Because it was able to identify these coal seams and fissures, thermal anomalies in the fire zone were "very obvious".
"To implement fire suppression more effectively, coal fire detection is a key technology ... The scopes and locations of the fire zones were preliminarily delineated by this method, which provides an accurate basis for the development of fire suppression projects."
The fires in HCM were triggered by human interference, noted the researchers. Random mining and the excavation of small coal kilns have altered the natural environment of coal seams, making them easier to oxidize and spontaneously combust.
The team, which worked with Zheng Luo and Tao Guan from the state-backed Aerial Photogrammetry and Remote Sensing Bureau, said airborne thermal infrared (TIR) remote sensing alone has also not proved suitable for finding smaller fires. Using imaging systems mounted on manned airborne platforms was also limited by high operational complexity and costs.
A Digital orthophoto map (DOM) of the HCM and superimposed thermal anomaly