Separating sea surface and land areas in an optical remote sensing image is  very challenging yet of great importance to the coastline extraction and subsequent inshore and offshore object detection. The state-of-the-art methods often fail when the land and sea areas share complex and similar intensity and texture distributions. In this paper, we propose a graph cut (GC) based supervised method to segment the sea and the land from natural-colored (red-green-blue, RGB) images. Firstly, an image is pre-segmented into superpixels and a graph model with the superpixels as its nodes is constructed. Then each superpixel node is encoded by a multi-feature descriptor, and a probabilistic support vector machine (SVM) is trained for automatic seed selection. These seeds will be used to build the prior model for GC. When modelling boundary term in GC, we incorporate edge information between neighboring superpixels to get finer results for some thin and elongated structures.

Experiments on a set of natural-colored images from Google Earth demonstrate that our method outperforms the state-of-the-art methods in terms of  quantitative and visual performances.