Imaging spectrometry data correlated to hydrocarbon microseepage

Modular Airborne Imaging Spectrometer (MAIS) data were used to map hydrocarbon microseepages in the Weibei Depression, People's Republic of China, as an aid to petroleum exploration. To convert the radiance data to reflectance, the Empirical Line Method was used and the resulting data were similar to the field spectra. After first delineating the wheat fields, three bands (at 719.75 nm, 739 nm and 758.25 nm) were used to map the pixels that had a red shift. A neighbourhood summation function was applied to evaluate which pixels were more likely to be anomalies. The non-systematic geometric distortions were corrected with the aid of linear features in the image and subsequently the systematic geometric distortions were corrected using ground control points. Ethane concentrations of 217 soil samples were used to assess the mapping result. It appears that high ethane concentrations in the map area are positively correlated to red-edge shift, which suggests that a high ethane concentration in soil may cause red-edge shift in wheat spectra. However, sub-surface structure and stratigraphy must be considered as well when analysing MAIS data.