THE METHODS OF EXTRACTING WATER INFORMATION FROM SPOT IMAGE

Some techniques and methods for deriving water information from SPOT-4 (XI) image were investigated and discussed in this paper. An algorithm of decision-tree (DT) classification which includes several classifiers based on the spectral responding characteristics of water bodies and other objects, was developed and put forward to delineate water bodies. Another algorithm of decision-tree classification based on both spectral characteristics and auxiliary information of DEM and slope (DTDS) was also designed for water bodies extraction. In addition, supervised classification method of maximum-likelyhood classification (MLC), and unsupervised method of interactive self-organizing dada analysis technique (ISODATA) were used to extract waterbodies for comparison purpose. An index was designed and used to assess the accuracy of different methods adopted in the research. Results have shown that water extraction accuracy was variable with respect to the various techniques applied. It was low using ISODATA, very high using DT algorithm and much higher using both DTDS and MLC.