新型水体指数的构建及在滨海湿地水域提取中的有效性验证

湿地是“地球之肾”，对地球生物生存具有重要意义。由于湿地水域面积的破碎化程度高，常规利用遥感技术提出的水体指数不够有效，简单快速的实时监测技术还需完善。以2009年杭州湾湿地的Landsat TM影像为基础数据，选择不同水域类型，构建新型水体指数（water zscore-band5，WZ5），与常用的改进的归一化差异水体指数（modified normalized difference water index，MNDWI），混合水体指数（combined index of NDVI and NIR for water body identification，CIWI）进行对比，分析各指数湿地水域信息提取的准确性和完整性。结果表明:所构建的指数WZ5水体信息提取精度优于MNDWI和CIWI，特别是含有大量塘基且分布复杂的水产池塘破碎区，WZ5计算水体与塘基的区分度为41.78%，大于MNDWI（21.59%）和CIWI（34.56%）；总体识别精度为82.00%，也大于MNDWI（58.00%）和CIWI（77.00%）。利用WZ5对遥感影像进行水体增强的方法，不仅能够很好地提取出湿地开阔水域的水体信息，边缘清晰可靠；对于破碎水域，WZ5水体提取精度最高，并且相比基于复杂数学理论的分类提取过程，操作相对简单，易于推广，能够较好地提高湿地水域实时监测的精度。

WZ5 water index and validation of its effectiveness in a coastal wetland water extraction

Wetlands have a high degree of fragmentation with their water areas. While it is not effective enough to use an existing water body index based on routine remote sensing technology so far. This study tries to find an improvement with a simple and fast real-time monitoring technology. Based on different types of water bodies from a Landsat TM image of Hangzhou Bay Wetlands in 2009, An analysis was conducted for water extraction with a new indexWater Zscore-Band 5 (WZ5)], and compared to the Modified Normalized Difference Water Index (MNDWI) and the Combined Index of NDVI and NIR for Water Body Identification Index (CIWI) which were commonly accepted. The extraction result was verified by random sample of points in research area. Results showed that for the broken zone of an aquatic pond with a large pond base and a complex distribution, the extraction accuracy of the WZ5 index, having a degree of distinction between water and pond of 41.78%, was better than MNDWI (21.59%) and CIWI (34.56%). Overall accuracy of the WZ5 index was 82.00%, which was also better than MNDWI (58.00%) and CIWI (77.00%). The WZ5 index not only extracted precise water information well with a clear and reliable edge, but also had very high extraction accuracy. Compared to a classification process based on complex mathematical theory, operation was relatively simple with a favorable application. Thus, WZ5 could improve accuracy for real-time monitoring of wetland water bodies.