Lagoon detection, platform reef analysis in Jakarta, Indonesia using Landsat-8

Spectral signature in remote sensing derived from digital image processing is a breakthrough in generating geomorphic information. The implementation of this image processing technique requires a wider range of objects and approaches, especially for shallow sea waters and small islands. A lagoon in the coral reef ecosystem is representative of its characteristics and suitable for monitoring both natural and artificial degradation. The lagoon itself is also essential for fisheries resource management and tourism. This study aims to analyze the suitability and relevance of image processing used to detect lagoon. The study area is in Semakdaun Island and Panggang Island, Jakarta marine national park, which is located in one of four classes for small islands cluster based on tectono-genesis. The class is continental platforms and back arc regions in Indonesia, whereas it is dominated by tectonic types. This area is also correlated with the platform reef. Landsat-8 imagery was processed by OIF (Optimum Index Factor) calculation to find the effective composite bands in detecting lagoon. Then continued with the line transect method that was used across the reef to find spectral graphic of lagoon and non-lagoon. The bathymetry data and selected composite bands used for validation. Visual interpretation to the digital image was applied to this study in terms of analyzing the lagoon phase and platform reef landform classification. The results showed that the selected band composite image in RGB namely SWIR 1-Coastal aerosol-Green (band 6-1-3) was the best combination in differentiating lagoon and non-lagoon. The spectral graphic in Semakdaun Island showed more dynamic than the graph belonged to Panggang Island. This high dynamic spectral graphic pattern indicates the higher phase of lagoon condition. The RGB composite 6-1-3 indicates color differences between lagoon and non-lagoon. Visual interpretation of spectral graphic and composite image was used then to find lagoon condition phase and analysis of platform reef landform classification.