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    城市化地区Landsat水体指数适用性分析

    Interpretation and Applicability Analysis of Landsat Water Index in Urbanized Areas

    • 摘要: 遥感水体指数是地表生态环境分析的重要基础,在大规模水体提取与水文监测中起关键作用.多种水体指数研究集中于大尺度、短历时、非城市化为主的区域,而对于城市化地区的水体指数适用性问题却一直困扰着城市水体的提取.针对常用水体指数(TCW、NDWI、MNDWI)和改进的新型水体指数(WI2015、AWEInsh、ANDWI、MBWI、WI2020),搜集深圳市1986~2020年逐月Landsat影像,以建筑阴影、亮建筑、暗建筑、滩涂噪声和山体阴影5种案例区为例,分析不同水体指数在城市地表覆被噪声区的解译能力.结果表明:(1)水体指数的生产者精度与用户精度呈负相关(Otsu阈值),TCW、NDWI、ANDWI、AWEInsh可有效过滤建筑类噪声和山体阴影,但无法识别细小河流水体,MNDWI、WI2015、MBWI、WI2020则相反;(2)光谱变换型和差值型水体指数考虑多波段的绝对值,可分离度较低,适用于高质量影像制图,比值型和逻辑运算型水体指数计算多波段的相对值,更适用于长序列监测;(3)多案例、多时相的案例区抽样验证方法有效突显出水体指数的解译能力和阈值适用性,城市地区NDWI适用性最强,非城市地区WI2020提取精度最高.上述研究为城市水文监测过程的水体指数选取、精度验证提供了一定的理论参考和实践依据.

       

      Abstract: Remote sensing water indices are important basis for surface eco-environment analysis,and are critical to large-scale waterbody interpretation and hydrological monitoring.A variety of water indices focus on large-scale,short-term,non-urbanized regions,while the extraction of urban water bodies has been plagued by the applicability of these indices.The study collected Landsat images from 1986 to 2020 in Shenzhen city,and adopted three commonly used water indices(TCW,NDWI,MNDWI) and five improved water indices(WI2015,AWEInsh,ANDWI,MBWI,WI2020).The interpretation ability of these water indices in the urban noise area were analyzed by taking five regions of building shadow,high albedo building,low albedo building,tidal-flat and mountain shadow as examples.The results show that:(1)Producer accuracy of water indices are negatively correlated with user accuracy(Otsu threshold),and TCW,NDWI,ANDWI,AWEInsh can effectively filter architectural noise and mountain shadow,but unrecognize small river water bodies,MNDWI,WI2015,MBWI,WI2020 are the opposite;(2)The spectral transformation type and difference type water indices consider the absolute value of multiple bands with low separability,and they are suitable for high-quality image mapping.The ratio type and logical operation type water indices calculate the relative value of multiple bands,and suitable for long-term monitoring;(3)The method of multi-temporal sampling verification in typical cases highlights the interpretation ability and threshold applicability of water indices,and the NDWI is most applicable in urbanized areas,while the WI2020 achieves the highest interpretation accuracy in non-urbanized areas.The above research provides a certain theoretical reference and practical basis for the selection of water index and accuracy verification for urban hydrological monitoring.

       

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