地表水面精确提取是研究地表水质和水量变化的重要基础。斯里兰卡是"21世纪海上丝绸之路"的重要参与国，年降雨量丰富，但时空分布不均，斯里兰卡人民长期用水困难，研究斯里兰卡地表水体有助于斯里兰卡民生问题的解决。斯里兰卡国内散布着大量的小型水库和坑塘，这些小面积水体易受周边环境因素影响而提取困难。基于2017年7月斯里兰卡中东部地区的哨兵（Sentinel）1/2号卫星影像，对比分析单波段法、水体指数法和监督分类等水体提取方法的精度和存在的问题。结果表明，归一化水体指数法NDWI的准确率最高，分类精度达94%。
The accurate extraction of surface water is an important basis for studying the changes of quality and quantity for surface water. Sri Lanka is one of the most important participating countries along "21st-Century Maritime Silk Road".Rainfall is abundant in Sri Lanka. However, due to uneven spatial and temporal distributions of the rainfall, people in Sri Lanka have a long-term difficulty in using water. Study on surface water is helpful for solving the problem of people's livelihood in Sri Lanka. There are a large number of small reservoirs and ponds scattered throughout the country,but it is difficult to extract small area water which is affected by surrounding environment. In this paper, the accuracies and existing problems of water extraction methods, such as single-band method, water body index method, and supervised classification method, were compared and analyzed based on Sentinel 1/2 satellite image in July 2017 in eastern Sri Lanka. The analysis results show that the normalized difference water index (NDWI) method has the highest accuracy with a classification accuracy of 94%.
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