The users of RADARSAT images need ground control points (GCPs) to geometrically correct or to match the images. But the selection of GCPs has been done manually until now. Thus, the quality of the rectified images depends on the ability of the operator to select high quality GCPs. This selection is more difficult in SAR images due to their particular geometry and radiometry. We worked on the development of a method and software to automatically identify high quality GCPs in RADARSAT images using data from a topographic database. Different strategies have been elaborated to fit with different contexts. These strategies are gathered into two approaches used to match the two data sources: the vector and the raster approach. For both approach, a method has been developed to automatically identify GCPs from the category "stretches of water". A GCP software prototype has also been implemented according to these methods.

Users of Radarsat images need ground control points (GCPs) to georeference their images, to rectify them, and to fuse these images. Because the selection of GCPs is usually done manually, the efficiency of the process depends on the ability of the operator to select a GCP. The present paper introduces a new method to automatically identify GCPs in Radarsat images using a topographic database. First, different strategies are elaborated to fit different contexts (topography, cost, availability of data, etc.). These strategies are then grouped in two approaches, i.e., vector-based data matching and raster-based data matching. Both approaches rely on matching feature classes (in ISO/TC211 parlance), e.g., matching "water bodies" or matching "roads intersections" from the image with their equivalent on the topographic database. A user of this method can easily follow the various steps of the GCPs selection process with the support of software tools. This paper presents in detail the method developed to select GCPs with the feature class "water body" and the vector-based matching approach, and also presents some applications.