以东沙环礁为研究区域,选取1999年Landsat -7 ETM-+-影像数据和2001年、2009年Landsat -5 TM影像数据为主要数据源,应用基于统计学习理论的支持向量机(SVM)分类技术,通过选择训练时间较短的“一对一”SVM方法和RBF核函数,对3个年度的影像数据进行珊瑚礁信息提取.结果表明:2009年东沙环礁珊瑚礁面积为140,93 km2；1999-2009年,东沙环礁珊瑚礁面积减少了17.54 km2,珊瑚礁破碎化、白化现象趋于明显,珊瑚礁退化处于中期阶段.空间分辨率的提高可得到更准确详尽的珊瑚礁信息,尤其对小面积珊瑚礁的信息提取.%One Landsat - 7 image of 1999 and two Landsat - 5 images of 2001, 2009 were chosen to map and detect changes of coral reef community at Dongsha atoll. As the support vector machine (SVM) is very attractive for the classification of remotely sensed data, it was introduced into the extraction and classification of the coral reefs. Considering the training time and classification accuracy, 'one against one' and,radial basis kernel function (RBF) were determined. The results show that the total area of the coral reefs at Dongsha atoll is about 140. 93 km2 in 2009. From 1999 to 2009, the coral reefs were in the intermediate stage of degradation, because their areas decreased 17. 54 km2 and they behaved evident fragmentation. High spatial resolution images are helpful to extract coral reefs properly and accurately, especially to minor area of coral reefs.
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