AIRBORNE SAR AND LANDSAT MSS AS COMPLEMENTARY INFORMATION SOURCE FOR GEOLOGICAL HAZARD MAPPING

A comparative study has been made of the usefulness of Landsat and air borne radar images. The study area is situated in the Middle Magdalena Valley of Colombia. It consists of a folded sedimentary sequence of U pper Cretaceous to Lower Tertiary rocks, partially covered by extensiv e volcanic lahar and alluvial fan material. To obtain the full benefit of the spectral information from Landsat and the textural and pattern information from radar, a combined image was produced using the hue a nd saturation information from Landsat data and the intensity values f rom radar data. A clear differentiation between old lahar deposits and the recent one caused by the Nevado del Ruiz eruption of 1985 was pos sible on SAR images. The synergistic radar imagery, particularly used in stereo, is very useful for prediction of future lahar routes and vo lcanic risk evaluation.