Michael J. Starek Texas A&M University-Corpus Christi, Conrad Blucher Institute for Surveying and Science
Tianxing Chu Texas A&M University-Corpus Christi, Conrad Blucher Institute for Surveying and Science

23F

Over the recent years, lidar sensor technology has rapidly evolved and miniaturized. The reduced sensor size and weight has allowed lidar sensors to be carried onboard small unmanned aircraft systems (UASs). Compared with traditional airborne lidar mapping, UAS platforms offer more flexibility in terms of flight design and data collection, rapid response capabilities, and reduced cost at local geographic scales. Structure-from-motion (SfM) photogrammetry represents an alternative to airborne lidar to derive 3D point cloud data using passive RGB cameras. SfM relies on adequate image overlap to extract key point correspondence from image sequences to reconstruct the 3D scene. This “single return” point cloud approach is susceptible to false parallax induced from moving features between overlapping images (such as vegetation moving in the wind) and to poor feature correspondence in areas where the image texture is highly uniform or poor. In contrast, pulsed ranging employed by lidar is not influenced by feature movement in the scene, and lidar can employ multiple return echo detection. This multi-return capability is particularly advantageous for below canopy elevation modeling. In this paper, initial results on the testing and evaluation of a single-rotary UAS integrated with a long-range, multi-return lidar sensor will be presented. The study primarily focuses on: 1) description of the platform and enabling technology (lidar/IMU/GNSS) of the fully integrated UAS solution, 2) sensor calibration and initialization, and 3) description of data collection and processing workflow. Finally, a comparison between 3D point clouds acquired over a scene mapped using UAS-SfM and UAS-Lidar will be performed. Assessment will focus on differences in representation of the underlying terrain and elevation accuracy.

12:15 Evaluation of UAS Lidar vs UAS SfM – A Case Study, Michael Starek