A nationwide automatic satellite image registration system

A system for automatic ground control point measurement and rectification of satellite images to a nationwide reference database has been developed. As reference for the rectification a database consisting of more than three hundred thousand features covering the whole Finland has been created. These features are islands and lakes extracted from the nationwide Land Cover Classification, produced from Landsat Thematic Mapper (TM) images. Also the use of digital maps and image mosaics has been tested. Lakes and islands are extracted from the satellite image to be rectified. Their attributes are compared to those in the reference database. Using feature based matching and robust estimation a few hundred ground control points of subpixel accuracy are selected to the rectification. Images of different resolution can be measured automatically using this system. It has been tested using SPOT, Landsat TM and NOAA AVHRR imagery. The search for ground control points takes only a few minutes per satellite image. The accuracy of the result has proved to be at least as good as when measuring the control points manually. The method is tested by computing the parallaxes between the reference features and the rectified images