Boresight calibration of a multi-sensor system for UAS photogrammetry

The calibration of multi-sensor systems to facilitate direct georeferencing is essential for ensuring high accuracy photogrammetry products. Integrated solutions require estimations and compensations of misalignments - positional and/or angular - between individual sensors. This paper discusses the calibration of angular misalignments, or boresight angles, caused by the inaccurate alignment of the image and body frame. Such a task is performed via field calibration, enabling us to estimate boresight angles using data from a real UAS mission. A UAS equipped with a custom-built multi-sensor system, comprising a state-of-the-art technology in navigation systems, was employed to collect aerial data across the test area. In order to obtain reference data for the calibration, thirty ground control points were distributed in the area, and the exterior orientation of every image was estimated through aerial triangulation. In addition to the boresight calibration, the attitude measurement accuracy was assessed and discussed.