Coral Reef Patch Mapping
|關鍵字:||趨勢面;分割;珊瑚礁;trend surface;segmentation;coral reef|
Coral reef is formed by the corals’ growth and accumulation. According to the geography, it can be divided into two parts: the flat and the slope. By its construction, coral reef can be divided into three types: the fringing reef, the barrier reef and the atoll reef. The atoll reef areas on Dongsha Island are what being researched in this study, and this research aims at detecting and drawing the location of reefs around the Dongsha atoll area. The data used in this research includes digital elevation model (DEM) and satellite images. Three 1/5000 drawings had been chosen as the researched area depending on the characteristics of terrain, and their locations are: the middle of the lagoon area, the junction of the lagoon and the reef plat, and the reef plat. Trend surface analysis and object based segmentation are the two reef location-detecting ways that this research uses. The first one can only detect the location of reefs in DEM, while the second can detect both in DEM and the satellite images. The detected results will be compared with the real situation basing on the human observation of DEM and the sketched map of the reefs distribution. According to the different ways and combinations, it proves that object based segmentation in combination of the image of DEM, serves best. Among the five different analyses, the best one is DEM weight of 4 and image weight of 1. The average accuracy of the three areas is above 0.97, and the Kappa coefficient is higher than 0.84.