Determination of the Uav Position by Automatic Processing of Thermal Images

If images acquired fromUnmanned Aerial Vehicles (UAVs) need to be accurately geo-referenced, the method of choice is classical aerotriangulation, since on-board sensors are usually not accurate enough for direct geo-referencing. For several different applications it has recently been proposed to mount thermal cameras on UAVs. Compared to optical images, thermal ones pose a number of challenges, in particular low resolution and weak local contrast. In this work we investigate the automatic orientation of thermal image blocks acquired from a UAV, using artificial ground control points. To that end we adapt the photogrammetric processing pipeline to thermal imagery. The pipeline achieves accuracies of about ± 1 cm in planimetry and ± 3 cm in height for the object points, respectively ± 10 cm or better for the camera positions, compared to± 100 cm or worse for direct geo-referencing using on-board single-frequency GPS.