基于混合像元分解的武汉市湖泊面积变化监测

Dynamic Monitoring of Lake Areas in Wuhan Based on Mixed Pixels Decomposition

以中等分辨率LandsatTM/ETM+为数据源的常用水体提取方法有阈值法、谱间关系法、归一化水体指数法和分类法,然而这些方法都未考虑混合像元的影响。遥感影像上不可避免的存在着混合像元,这使得基于像元的遥感信息提取精度难以满足较高精度应用需求。首先利用混合像元线性光谱分解方法从2006年武汉地区LandsatTM影像上计算得到了东湖水面面积,并与传统基于像元的方法处理得到结果进行对比,发现前者精度更高。随后,又利用混合像元线性光谱分解法从多时相Landsat TM/ETM+影像上提取了1995-2006年武汉市主要湖泊水域面积变化信息,并对监测结果进行分析。结果表明武汉市主城区湖泊面积在11年间普遍呈现出不断减少的趋势,湖泊萎缩强度指数ILLI呈现出时空分布不均的特点。

Conventional methods including threshold method,spectral structure method,normalized difference water index and classification method are used to delineate and extract water body from TM/ETM＋ data collected by Landsat with medium spatial resolution.However,none of them take the impact of mixed pixel into account.Mixed pixels,unavoidable on remote sensing image,generally result in low precision of pixel-based information extraction,which makes it hard to meet the requirements of highly accurate applications.In this article,the water area of the East Lake is calculated based on linear spectral unmixing method from Landsat TM image obtained in 2006.The result proves to be more accurate compared with those by pixel-based methods.Furthermore,linear spectral unmixing method for mixed pixel is exerted on varied Landsat TM/ETM＋ imageries to monitor the shrink of lake area in Wuhan from 1995 to 2006.The monitoring results demonstrate that lake areas in Wuhan decreased continuously during this period,and the Index of Lake Loss Intensity（ILLI） was unevenly distributed across time and space.