A Case Study of UAS Borne Laser Scanning for Measurement of Tree Stem Diameter

Abstract

Diameter at breast height (DBH) is one of the most important parameter in forestry. With increasing use of terrestrial and airborne laser scanning in forestry, new exceeding possibilities to directly derive DBH emerge. In particular, high resolution point clouds from laser scanners on board unmanned aerial systems (UAS) are becoming available over forest areas. In this case study, DBH estimation from a UAS point cloud based on modeling the relevant part of the tree stem with a cylinder, is analyzed with respect to accuracy and completeness. As reference, manually measured DBHs and DBHs from terrestrial laser scanning point clouds are used for comparison. We demonstrate that accuracy and completeness of the cylinder fit are depending on the stem diameter. Stems with DBH > 20 cm feature almost 100% successful reconstruction with relative differences to the reference DBH of 9% (DBH 20-30 cm) down to 1.8% for DBH > 40 cm.

Detecting shrub encroachment in seminatural grasslands using UAS LiDAR

“…The variance for example will be set relative to a normal‐based plane. Measurements of shrub growth form may be difficult to conduct and define in field‐based surveys; hence, there is a focus on retrieving metrics as, for example, diameter at breast height (DBH; Wieser et al, 2017). Nonetheless, the high importance of Pseudowaveform for classifying shrub species suggests that shrub growth form is highly relevant for distinguishing species.…”

“…UAS LiDAR systems provide new opportunities to provide ultrahigh point density (>1,000 pts/m 2 ) on demand; hence, mapping vegetation structure with high detail and sampling frequency becomes possible across areas of up to several square kilometers. UAS LiDAR systems have been used to detect individual trees and to measure metrics such as height and stem diameter (Wallace, Lucieer, Watson, & Turner, 2012; Wieser et al, 2017). The ability to detect single trees has been found to increase with higher point densities (Wallace, Lucieer, & Watson, 2014), and Balsi, Esposito, Fallavollita, & Nardinocchi, 2018 could contrast different shapes of horizontal overlapping trees using information from the whole volume of points in the point cloud.…”

Concept and Performance Evaluation of a Novel UAV-Borne Topo-Bathymetric LiDAR Sensor

“…Since 2013, the study area has been repeatedly captured with various topo-bathymetric laser scanners mounted on manned aircraft for monitoring river morphodynamics and instream habitats [4] as well as with UAV-borne topographic sensors for detailed analysis of the riparian area [66,67]. At the same site, first performance evaluations of a UAV-borne bathymetric laser range finder were carried out [61].…”

Monitoring Selective Logging in a Pine-Dominated Forest in Central Germany with Repeated Drone Flights Utilizing A Low Cost RTK Quadcopter

“…Due to the wide scanning angle, the high point cloud density, and the possibility to fly tracks with great overlap between the scans, shadowing hardly occurs. In contrast to conventional airborne LiDAR and UAS-borne SfM point clouds, stems can be sensed precisely [40]. Although the full potential of UAS-borne LiDAR is not yet fully exploited, similar tree detection rates achievable with multiple TLS scans can be expected, with the advantage of capturing larger areas in a shorter time, while having no GNSS constraints [38,40].…”

“…In contrast to conventional airborne LiDAR and UAS-borne SfM point clouds, stems can be sensed precisely [40]. Although the full potential of UAS-borne LiDAR is not yet fully exploited, similar tree detection rates achievable with multiple TLS scans can be expected, with the advantage of capturing larger areas in a shorter time, while having no GNSS constraints [38,40]. Nevertheless, it is questionable whether UAS-borne LiDAR systems will be widely used in the near future for the detection of selective logging.…”