Proper synchronization of geospatial metadata in motion imagery and its evaluation
Motion imagery with geospatial metadata are recordings that are used to provide information about the observed scene. Given the comparably high speed and agility of the sensor platform (usual some kind of aircraft), metadata has to be synchronized very accurately to each individual recorded image to yield accurate results. The quality of the geospatial metadata can be evaluated by a 3D reconstruction of a motion imagery sequence (with software like Agisoft Metashape1 or COLMAP2, 3) and comparison of the reconstructed camera poses with the camera poses derived from the metadata. The obtained results so far suggest that a miss synchronization between the video frames and the metadata is often one of the largest sources of inaccuracies of the geospatial metadata and one of the most easy to avoid. For this reason, we assembled our own system with a commercially available image sensor and metadata module that can be attached to a small aircraft and evaluated the quality of its metadata on a test flight. This article describes the used system and the result of the metadata calibration4 performed to evaluate the quality of the metadata and its synchronization to the image frames.