THE USE OF HIGH RESOLUTION SATELLITE TO STUDY A CORAL REEF HABITAT AT MANNAI ISLAND, RAYONG PROVINCE, THAILAND

摘要

Mannai Island at Rayong province is one of the most popular tourist places in Thailand. The monitoring of marine ecosystem changing in this areas, especially coral reef is very important. The use of high resolution satellite (QuickBird) to study a coral reef habitat at Mannai island is aim to 1) study a proper image processing technique for coral reef mapping, 2) compare image processing technique between Pixel base (A pixel is the smallest unit of a digital image. The term pixel is a contraction of picture element) and Object base (A group of connected pixels in a scene. Each image object represents a definite region in an image. Image objects can provide information about this definite image region) and 3) study a relation between coral group distribution and water depth using high resolution data, dive surveying and Acoustic Doppler Current Profiler (ADCP) which has bottom tracking and GPS connecting.In this study, researchers compared three different atmospheric correction methods that are Dark subtraction using satellite analysis software, Dark reflectance subtraction using Edward 1999's procedure and FLAASH model. The best image quality is derived from FLAASH model. Using FLAASH model, the output image is the sharpest and more flexible to adjust the variables i.e. surface albedo, surface altitude, water vapor column, aerosol and cloud optical depths, surface and atmospheric temperatures. The output image from FLAASH model was classified using two different techniques that are pixel base analysis (Maximum Likelihood) and object base analysis (Nearest Neighbor Classification). The image classification can be divided into four groups which are group of coral, rock, sand and deep water. In order that total accuracy of the pixel base analysis and object base analysis are 81.35% and 85.47% respectively. The most accuracy of pixel base analysis are deep water and rock while the object base analysis are coral and rock.In addition, the distribution of coral group in the shallow zone (0-100 m from the beach) found Zoanthid and sea grass at 1-2 m and 17 groups of coral at 1-7 m depth. The dominant coral groups are Mountain coral, Cauliflower coral, Staghorn coral and Brain coral. In the next zone (150-200 m from the beach) found sand, dead coral and sea fan at 7-10 m depth. The investigation of water quality in the study area is optimum for coral and other living things.