Detection of roads from satellite image using the optimal search

Since networks of main roads are basic information for classification of the use of the Earth´s surface, automatic detection of roads from satellite images is a very important problem. In this paper, a new detection theory is proposed which can overcome drawbacks of current theories and detect plural roads in an image with high speed and high precision. Firstly, a binary image representing edges of a given image is used to evaluate the possibility for a road to pass on each edge pixel. We propose an 8-direction filter, a clearing filter, and a parallel-edge-detection filter, which can compile insufficient local information to obtain global information enough to detect a road. After these filters, the possibility of a road passing on a edge pixel can be effectively evaluated. Secondly, by using the Hough transform and the optimal search method it is possible to detect a complete road. This detection theory does not depend on the size of image and can detect almost all the main roads in an image including intersecting and T-type roads