Visible–infrared and radar imagery fusion for geological application: a new approach using DEM and sun-illumination model

Radar-multispectral imagery fusion has been successfully used in several application fields. In this study, a new technique to merge an ERS-1 (Synthetic Aperture Radar precision image, SAR-PRI) image and a Landsat Thematic Mapper (TM ) image for the geological study of the western Aspromonte (southern Italy) was investigated. Spectral information provided by the TM image can be effectively combined with texture and pattern data from the radar imagery to produce a synergistic image. Landsat bands are normalized for shadowing effects using the semi-empirical Minnaert model and thereafter multiplied by the ERS1 image. The visible-infrared (VIR) and radar fused bands can be composed into colour images. This technique leads to the production of images in which the geologically relevant information were integrated. These images were compared with the imagery produced by the intensity-hue-saturation (IHS) transformation approach, commonly used for image fusion. The sun-illumination normalization method gives better results in image fusion, enhancing subtle spectral features. Compared to the individual images, the synergistic SAR-TM images produced by this technique improve the interpretation of lithology boundaries and recognition of structural features.