Mobile Laser Scanning with Low-Cost Navigation Sensors: Compensating for Low-Grade IMU with Dual-GNSS and Tightly-Coupled LiDAR

Abstract

Kinematic laser scanning enables efficient and accurate acquisition of 3D data, specifically point clouds. Transforming the laser ranging measurements from the scanner coordinate system to a georeferenced coordinate system requires integration with auxiliary navigation systems, in this case using GNSS (global navigation satellite system) and an IMU (inertial measurement unit). GNSS and IMU data are commonly fused via Kalman filter, and the resulting trajectory is used for georeferencing. Errors in the trajectory propagate through the georeferencing and cause discrepancies in the point cloud. To mitigate this, we present a holistic integration method incorporating GNSS, IMU and LiDAR measurements in a single adjustment, which can be seamlessly adapted to a setup with two GNSS receivers and antennas. This tight coupling of LiDAR and IMU together with the dual-GNSS setup allows the use of an ultra low-cost IMU while still achieving high-quality point clouds. We demonstrate this methodology on two datsets, where we discuss in particular the boresight calibration of such a system, and the impact of the LiDAR measurements and the dual-GNSS set-up on the trajectory and the point cloud.