Extraction of land cover information in tropical area for cartographic application using Radarsat imagery

A previous study has demonstrated the lack of up-to-date maps at the small and medium scales in tropical countries. Satellite radar imagery, because of relative insensitivity to weather conditions is an attractive source of information in these regions, characterized by an almost permanent cloud cover. This paper explores the cartographic application of Radarsat SAR imagery over tropical areas. Different Radarsat beam modes images are analysed with respect to their potential in providing pertinent information for cartography, in particular, different incidence angles (S1, S4 and S7) and different resolutions (F5, S7). The results show that the landscape unit discrimination can be improved by a combination of several angles reflecting the difference in scattering mechanisms: for example, the volume scattering will decrease more slowly than the surface scattering for increasing incidence angle. The urban area detection is enhanced with higher incidence angle resulting from an improved contrast with surrounding areas. Finally, as expected, the higher resolution allows a better analysis of the human made structures. Both the fine beam mode and the multi-incidence analysis of the standard beam mode allow an update of the 1/50000 maps