淤泥质潮滩水边线提取的遥感研究及DEM构建——以长江口九段沙为例

淤泥质潮滩通常是测绘"盲区"。本文讨论采用多时相陆地卫星提取潮滩水边线以此构建潮滩数字高程模型(DEM)的方法。探讨在不同潮情条件下,各光谱波段对淤泥质潮滩水边线判断的敏感性,分析表明沙质海岸与淤泥质海岸水边线的确定方法有较大差别。采用了GIS技术对提取的水边线赋予相应的高程值,该值采用研究区附近潮位站理论潮位推算卫星过境的瞬时潮位值,以此构建潮滩DEM,与近期实测资料进行对比:在106.2 cm-358.6 cm高程范围内,二者相对误差<0.5 m的区域占总面积约70%,0.5～1.0 m为20%,>1.0 m占10%。遥感构建DEM作为一种手段对实测资料的欠缺是一种补充,随着遥感技术的发展精度有望提高。

A Remotely Sensed Approach on Waterline Extraction of Silty Tidal Flat for DEM Construction, a Case Study in Jiuduansha Shoal of Yangtze River

Tidal flat as geographically terrestrial and oceanic transition area is generally not mapped, also called "mapping blank area". However, it has paramount significance due to containing rich land and biological resources. For this reason, this paper discussed an approach that was how digital elevation model (DEM) of tidal flat was established by a series of waterlines extracted from multi-temporal Landsat Thermal Mapper (TM) data. It was found that each TM spectral band has distinct sensitivity to waterline extraction, and short-wave infrared band is optimistic for waterline extraction based on sand-flat type, but not on silty-flat type. The attribute of sets of waterline from multi-temporal satellite data were assigned into tidal level value by the estimation from tidal station record while the satellite was passing through the studied area. Then, DEM from waterline extraction was built with GIS. Compared with the results of in situ mapping, relative error was less than 0.5 m in most regions, and mean error was 0. 18 m.