江苏近海岸水深遥感研究

以江苏近海辐射沙脊群海域为典型研究区,通过实测水深数据和水体光谱测量与分析,发现对应TM3和TM4波段的水体光谱反射率对水深信息敏感,线性相关系数分别达到-0.561和-0.694。结合多光谱遥感信息传输方程所推导出的水深信息对数反演模式,针对本研究区TM4和TM3波段数据所建立的水深预测模式的复相关系数R2为0.4793,对0-15m水深,预测水深和实测水深之间拟合较好。利用TM5波段反射率、出露沙洲反射率以及海水反射率的差异,通过建立掩膜图像,可较有效地对TM遥感图像进行水陆分离,提取TM图像中海水部分,进一步可通过常用的图像处理软件绘制每隔5m的TM水深遥感制图、等深线图。随着高空间、高光谱、高辐射分辨率遥感技术的发展,对浅海水域的水深和水下地形进行遥感探测的技术方法和应用将会不断地深入开展。

Study on Water Depth Extraction from Remote Sensing Imagery in Jiangsu Coastal Zone

This paper takes offshore sandbanks in Jiangsu Province as a typical study area.The reflectance of red and near infrared bands is sensitive to water depth based on the analysis of situ water depth and synchronously measuring water reflectance spectra.The linear correlation between depth and reflectance of Landsat TM1 and TM2 is-0.561 and-0.694 respectively.The water depth derived method based on the multispectral remote sensing transfer model shows that depth has linear relationship with the logarithm form of ratio of radiance(or reflectance) differences between deep water and two bands respectively,which are sensitive to water depth.TM4 and TM3 were found to be sensitive to water depth according to former analysis in this study and depth retrieval model was developed using reflectance of these two bands.The model(R2=0.4793) was tested to have good accuracy for depth less than 15m,whereas the predicted accuracy is unaccepted.The reflectance of TM5 combined with the spectra comparison between seawater and sand bank can be used to find the limit between seawater and other objects,which can be used to extract seawater in TM image.Then,water depth was computed by depth retrieval model in the study area.Fathom lines with 5m intervals can be detected through image managing software.With the development of high spatial,spectral and radiant resolution remote sensing technique,the research on shallow water bathymetry remote sensing method and its application will be under continuing investigation.