A simple method to recover the latency time of tactical grade IMU systems
Résumé
This paper investigates the problem of latency estimation between an IMU (Inertial Measurement Unit) and a LiDAR (Light Detection And Ranging). The latency is due to the IMU itself, but also to the acquisition software and hardware configuration, which is generally set-up by survey systems users. We propose a method for latency estimation, and we show that this method meets the accuracy requirements of most LiDAR survey applications. We present test results of our method on various acquisition systems and hardware configuration which demonstrate that it is able to identify very accurately the total IMU-LiDAR latency through a simple procedure. The principle of the method is to put the LiDAR-IMU in rotational motions, thanks to a rotating table. By scanning a spherical target at different angular velocities, we can observe position shifts of the target center from which we derive an estimate the IMU-LiDAR latency. The method we propose works without absolute positioning and is therefore not sensitive to nonmodeled errors coming from GPS geolocated data. We show that in estimating accurately the LiDAR-IMU latency, we can optimize the configuration of a mobile LiDAR survey system in order to enhance its robustness with respect to high motion dynamics of the survey platform.