Nitin Kumar Tripathi and Nyoman Radiarta
Space Technology Application and Research Program (STAR)
Asian Institute of Technology,
P.O. Box 4, Khlong Luang,
Pathumthani 12120, Thailand
Tel: 66-2-524 6392, Fax:66-2-524 5597
Email: [email protected]
Coral reefs form unique habitat along the coastal zone area in the benthic family. This ecosystem has an important setting among others ecosystems. However, very little information on maps showing the distribution of various benthic habitats in the coral reef is available. Remote sensing technologies have great potential in overcoming this information void. The advantage of this technique is relatively inexpensive and the numeric nature of the data enables the generation of final maps on various scales and at different levels of complexity. There are several complications associated with extracting valuable information about benthic habitat mapping from satellite imagery with confidence. This study evaluates the suitability of latest satellite in Landsat series: Landsat 7 ETM+ for investigating coral reef habitat in several small islands in Riau Archipelagos. The study area is located around three major islands (Mensanak, Medang and Benan Islands) and several smaller islands in Riau Archipelagos, Riau Province. This area is one of the Coral Reef Management (COREMAP) areas. Major habitats in this area are representative of the general environmental in the Riau Archipelagos. Therefore the findings of this study could be useful for large mapping of coral reef habitat along the islands. Present study is mainly dedicated to coral mapping on reef top areas in shallow water depths.
Bands 1 and 2 were used for mapping coral habitats in Mensanak Island because of their water penetration. Most types of bottom habitat can be seen clearly within this two band. Image enhancement techniques have been applied for extracting benthic habitats (biotic and abiotic) such as: spectral indices, water column correction and principle component analysis. Algorithms were developed to marginalize the bottom effects on spectral responses. Final classification using band thresholds are developed as color-coded image showing seven types of bottom habitats. The marine survey was conducted in January 2002 to validate the habitat map.