|
Centre for Remote Sensing and Department of Geology, Imperial College, London SW7 2BZ, UK
The NERC Geoscience community airborne remote sensing test site near Carboneras in southeast Spain is dissected by several flash flood drainage channels. These contain a variety of clastic debris types related to diverse source rocks in the catchment basins. As part of a larger study of source rock, regolith and drainage debris relationships, the spectral reflectance characteristics of debris types in braided flash flood channels have been used to map debris dispersion with remotely sensed imagery. The study is based upon 11 channel 7.5 m pixel Airborne Thematic Mapper (ATM) imagery acquired by NERC in May 1989. The objective of the research was to achieve optimum discrimination of channel debris types and to study the integration of distinctive source rock/regolith spectral signatures caused by progressive downstream mixing during transport.
Image processing enhances small spectral variations to improve discrimination of debris types. Imagery was masked to display only channel bed pixels and maximise spectral discrimination within drainage channels. Several enhancement techniques, including principal components and hue-saturation-intensity transformations, and decorrelation and contrast stretches, were then used to emphasise spectral differences among the debris assemblages in the channel beds. One of the most successful products is a selective principal components colour composite image. The image data are presented as a debris lithology distribution map.
