Update of Roads in Gis by Automatic Extraction from Aerial Imagery

Extracting roads from aerial imagery is important for the update of Geographic Information Systems (GIS), e.g., to capture new roads or to improve the geometric accuracy of existing roads. It can be broken down into two phases: First, old data is verified to determine which parts of the data have changed. Then, newly built roads are added. In this paper a two-phase approach consisting of automatic verification, as well as automatic road extraction is proposed. In the verification phase roads are searched for in the image along the axes given by the old data. This is done by using the gradient information of the image to localise possible roadsides. For the extraction of new roads a two-resolution approach with successive fusion has been developed. In a reduced version of the image center lines of roads are extracted, while in the original resolution roadsides are detected. The results of the two resolution levels are fused with a number of rules. Results of the proposed approach on aerial images are presented.