Abstract
Abstract. Unmanned Aerial System (UAS) technology is nowadays willingly used in small area topographic mapping due to low costs and good quality of derived products. Since cameras typically used with UAS have some limitations, e.g. cannot penetrate the vegetation, LiDAR sensors are increasingly getting attention in UAS mapping. Sensor developments reached the point when their costs and size suit the UAS platform, though, LiDAR UAS is still an emerging technology. One issue related to using LiDAR sensors on UAS is the limited performance of the navigation sensors used on UAS platforms. Therefore, various hardware and software solutions are investigated to increase the quality of UAS LiDAR point clouds. This work analyses several aspects of the UAS LiDAR point cloud generation performance based on UAS flights conducted with the Velodyne laser scanner and cameras. The attention was primarily paid to the trajectory reconstruction performance that is essential for accurate point cloud georeferencing. Since the navigation sensors, especially Inertial Measurement Units (IMUs), may not be of sufficient performance, the estimated camera poses could allow to increase the robustness of the estimated trajectory, and subsequently, the accuracy of the point cloud. The accuracy of the final UAS LiDAR point cloud was evaluated on the basis of the generated DSM, including comparison with point clouds obtained from dense image matching. The results showed the need for more investigation on MEMS IMU sensors used for UAS trajectory reconstruction. The accuracy of the UAS LiDAR point cloud, though lower than for point cloud obtained from images, may be still sufficient for certain mapping applications where the optical imagery is not useful.
Highlights
Unmanned Aerial Systems (UASs) are getting recently more interest in the mapping community
This work showed initial results of the performance assessment of the UAS LiDAR point cloud obtained with the Velodyne sensor
The analysis was executed to assess the performance of dual-frequency GPS and medium-grade mechanical systems (MEMS) Inertial Measurement Units (IMUs) sensors in the trajectory reconstruction for georeferencing LiDAR point cloud
Summary
Unmanned Aerial Systems (UASs) are getting recently more interest in the mapping community. They are offering similar products as traditional (manned) airborne systems but at lower costs. Some applications need active sensors (e.g. LiDAR) that require direct georeferencing approach using navigation sensor data. The navigation sensors, such as Global Navigation Satellite System (GNSS) receivers and Inertial Measurement Units (IMUs) that are used for controlling and navigating typical Unmanned Aerial Vehicles (UAVs) are of lower performance and are not able to provide enough accurate georeferencing data. With strong developments in MEMS sensor technology, the newest IMUs are approaching the tactical grade performance, which is the dominant grade in typical aerial mapping systems.
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