GNSS-based Time synchronisation of Stereo Images

Abstract. Achieving precise synchronization in stereo photogrammetry is essential for accurately reconstructing dynamic scenes. A setup was developed that consists of two Sony ILX-LR1 cameras synchronously triggered using accurate timing provided by a GNSS receiver. For assessing the synchronization accuracy of the two cameras, we designed and implemented a board with LEDs providing visual reference. The evaluation indicates that the camera’s latency between triggering and the actual image capture process is within 2.5 milliseconds (RMSE 562 us / max 2375 us / min -593 us).These minor latencies arise from internal camera processes that remain undocumented. Corrections could be applied based on the received signals from the camera to increase accuracy of the synchronization of cameras to be mostly better than 1 millisecond. The results validate the feasibility of precise synchronization for high-resolution, UAV-based stereo photogrammetry, ensuring minimal temporal discrepancies in image capture.