DETERMINATION OF THE UAV POSITION BY AUTOMATIC PROCESSING OF THERMAL IMAGES

Abstract. If images acquired from Unmanned 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.