Wang Zeng-liang, Zhu Rong, Zhang Zhi-jie, Yao Bao-dong, Zhang Li-juan, Gao Jie, Jiang Qing-wu
Department of Epidemiology, School of Public Health, Fudan University, Key Laboratory on Public Health Safety, Ministry of Education, Laboratory for Spatial Analysis and Modeling, School of Public Health, Fudan University; Center for GIS Training, School of Public Health, Fudan University, Shanghai 200032, China.
Zhonghua Liu Xing Bing Xue Za Zhi. 2012 Aug;33(8):823-7.
With Landsat TM remote sensing images, snail habitats in Poyang Lake region were identified, using two indices: the modified normalized difference water index (MNDWI) and the normalized difference vegetation index (NDVI).
Two Remote sensing images of both wet and drought seasons in Poyang Lake region were obtained. MNDWI and NDVI were extracted from the images respectively, to present the regions of "water in summer and land in winter" and the coverage of vegetation. By overlaying those two regions, the areas of potential snail habitats were drawn. Finally, sensitivities and specificities of the recommended methods were assessed and compared to that of the traditional methods for the sake of extracting the areas of snail habitats.
The threshold values of MNDWI for the wet and drought seasons were 0.34 and 0.58, respectively and the threshold value for NDVI of the drought season was 0.02. Sensitivity and specificity of our method were 95% and 100%, respectively, higher than the conventional approach (se. = 75%, sp. = 100%).
Joint application of MNDWI and NDVI seemed a better method to detect the snail habitats and could be used for the quantitative and automatic surveillance program on snails.
利用陆地卫星专题制图仪（TM）遥感影像，通过修正归一化差异水体指数（MNDWI）和归一化差异植被指数（NDVI）这两个指标识别鄱阳湖地区的钉螺栖息地。
获取鄱阳湖地区丰水期和枯水期的两幅遥感影像，分别提取影像中的MNDWI和NDVI，以呈现“夏季为水域、冬季为陆地”的区域以及植被覆盖情况。通过叠加这两个区域，绘制出潜在钉螺栖息地的面积。最后，评估并比较推荐方法与传统方法在提取钉螺栖息地面积方面的敏感度和特异度。
丰水期和枯水期MNDWI的阈值分别为0.34和0.58，枯水期NDVI的阈值为0.02。我们方法的敏感度和特异度分别为95%和100%，高于传统方法（敏感度 = 75%，特异度 = 100%）。
联合应用MNDWI和NDVI似乎是检测钉螺栖息地的更好方法，可用于钉螺的定量和自动监测计划。
