A method for reducing the effects of background radiation introduced into gaseous plume spectral data obtained by an aerial imaging sensor, includes capturing spectral data of a gaseous plume with its obscured background along a first line of observation and capturing a second image of the previously obscured background along a different line of observation. The parallax shift of the plume enables the visual access needed to capture the radiometric data emanating exclusively from the background. The images are then corresponded on a pixel-by-pixel basis to produce a mapping. An image-processing algorithm is applied to the mapped images to reducing the effects of background radiation and derive information about the content of the plume.