Automatic Exterior Orientation of Aerial Images in Urban Environments

We present an approach for automatic exterior orientation of aerial images which is based on the use of manhole covers as landmarks The approach includes two main procedures First a landmark extraction scheme which enables us to automatically detect and precisely localize many of the manhole covers visible in an image Second an automatic matching procedure which robustly and e ciently matches constellations of detected landmarks with the correct landmarks from a cadastral database By combining both methods we are able to automatically generate a large number of landmark correspondences per image which allows for a reliable estimation of the exterior orientation parameters