Automated GCP detection for SAR imagery: road intersections

Road intersections are very good ground control points in a SAR image because they can be obtained from intersecting road segments even when the intersections themselves are not observed. In a previous study, a Hough transform-based approach was developed for detecting intersections from a single-look ERS-1 SAR image. A similar Hough transform-based approach has been applied to detect road intersections in a 6-look ERS-1 SAR image. In the case of multi-look images, however, there are no pure road pixels because roads are thinner than the resolution size and the pixels that include road information are greatly affected by surrounding objects. More spatial information and even approximate road map information are required to improve the capability to detect road intersections. It is found that broad intersections ca be automatically determined from a multi- look image and the accuracy of the location of road intersections may be estimated from the heights of sharp peaks in Hough space.