A comparison of Landsat ETM plus , SPOT HRV, Ikonos, ASTER, and airborne MASTER data for coral reef habitat mapping in south pacific islands

The performances of the Landsat-7 ETM+, ASTER, SPOT HRV, and Ikonos satellite sensors and the airborne MASTER (MODIS-ASTER simulator) were compared for coral reef habitat mapping in South Pacific reefs. This unique image data set provided different spatial resolution (4 in for Ikonos to 30 in for Landsat-7 ETM+), spectral resolution (two visible bands for SPOT-HRV to five visible bands for MASTER) and digitization (8-16 bits). We focused on two islands (Tahiti and Moorea, French Polynesia) with barrier and fringing structures representative of reefs of South Pacific volcanic islands. Five levels of benthic habitat complexity were defined (with three, four, five, seven, and nine classes). Using a supervised maximum likelihood algorithm, the comparisons suggested several trends in sensor performances. Overall accuracies of Landsat-7 ETM+ compared well with sensors with higher spatial (Ikonos) or spectral (MASTER) resolution for low or moderate habitat complexity mapping. For high-complexity mapping (nine classes), Ikonos performed best, suggesting that high spatial resolution is important. For low- and moderate-complexity mapping, MASTER performed best, suggesting that spectral resolution and digitization seem more critical. However, these trends must be discussed cautiously in the light of various factors before any generalization can be made. These factors include issues in reconciling-scaling ground-truth data at multiple spatial and thematic scale, reefs specificities, and environmental conditions during image acquisition.