Road Roundabout Extraction from Very High Resolution Aerial Imagery

Road roundabouts, as a class of road junctions, are generally not explicitly modelled in existing road extraction approaches. This paper presents a new approach for the automatic extraction of roundabouts from aerial imagery through the use of prior knowledge from an existing topographic database. The proposed snake-based approach makes use of ziplock snakes. The external force of the ziplock snake, which is a combination of the Gradient Vector Flow force and the Balloon force, is modified based on the shape of the roundabout central island to enable the roundabout border to be delineated. Fixed boundary conditions for the proposed snake are provided by the existing road arms. A level set framework employing a hybrid evolution strategy is then exploited to extract the central island. Black-and-white aerial images of 0.1 m ground resolution taken over suburban and rural areas have been used in experimental tests which have demonstrated the validity of the proposed approach.