Mangrove mapping in North-Western Madagascar using SPOT-XS and SIR-C radardata

Within the framework of an environmental impact study of aquaculture activi ties in the coastal marsh of Mahajamba (North-Western Madagascar), an asses sment of the environmental conditions existing prior to the onset of aquacu lture activities (production began in October, 1993) is essential. To this end, the area was mapped using SPOT-XS data, which made it possible to defi ne the main ecodynamic tendencies of the mangroves before the development o f the rearing ponds. The aim was then to implement fast, precise and reliab le mapping methods, making it possible to follow mangrove alterations resul ting from these aquaculture activities. Analysis of the radiometric behavio ur of the various plant formations of the marsh, based on SIR-C radar data, revealed that the discrimination between these formations is easier when t he frequency used is low and the polarization is crossed. Thematic analysis using textural classification was carried out with the L-band and polariza tion VH. The results generated are promising insofar as the mapping of mang roves is concerned with a fast treatment time and acceptable precision of t he results.