Observing ecosystems with lightweight, rapid‐scanning terrestrial lidar scanners

Abstract

A new wave of terrestrial lidar scanners, optimized for rapid scanning and portability, such as the Compact Biomass Lidar (CBL), enable and improve observations of structure across a range of important ecosystems. We performed studies with the CBL in temperate and tropical forests, caves, salt marshes and coastal areas subject to erosion. By facilitating additional scanning points, and therefore view angles, this new class of terrestrial lidar alters observation coverage within samples, potentially reducing uncertainty in estimates of ecosystem properties. The CBL has proved competent at reconstructing trees and mangrove roots using the same cylinder-based Quantitative Structure Models commonly utilized for data from more capable instruments (Raumonen et al. 2013). For tropical trees with morphologies that challenge standard reconstruction techniques, such as the buttressed roots of Ceiba trees and the multiple stems of strangler figs, the CBL was able to provide the versatility and the speed of deployment needed to fully characterize their unique features. For geomorphological features, the deployment flexibility of the CBL enabled sampling from optimal view-angles, including from a novel suspension system for sampling salt marsh creeks. Overall, the practical aspects of these instruments, which improve deployment logistics, and therefore data acquisition rate, are shown to be emerging capabilities, greatly increasing the potential for observation, particularly in highly temporally dynamic, inaccessible and geometrically complex ecosystems. In order to better analyze information quality across these diverse and challenging ecosystems, we also provide a novel and much-needed conceptual framework, the microstate model, to characterize and mitigate uncertainties in terrestrial lidar observations.

Examination of the Potential of Terrestrial Laser Scanning and Structure-from-Motion Photogrammetry for Rapid Nondestructive Field Measurement of Grass Biomass

“…However, it is the least accurate. The CBL is a new generation of TLS that is inexpensive and optimized for rapid scanning and portability [44]. It took less than 10 min to set up and complete the four CBL scans for each plot.…”

“…The compact biomass LiDAR (CBL), built by the University of Massachusetts Boston, is a new generation of TLS that is inexpensive and optimized for rapid scanning and portability [44]. It uses a SICK LMS151 LiDAR and records the first and last returns at 905 nm over a 360 • horizontal and 270 • vertical scan in less than 35 s. It has a 0.25 • angular resolution and a 0.86 • beam divergence and a maximum range of 40 m. The CBL was placed on a tripod and oriented with a level so that the resulting x, y point cloud was in the horizontal plane.…”

Developing a site based index of vegetation structure complexity from terrestrial laser scanner data

“…TLS has the potential to rapidly acquire and create a 3D permanent record of vegetation structure. By developing a rapid method of vegetation condition assessment using TLS it will be possible to inventory a larger number of sites across broader areas (Paynter et al, 2016;Newnham et al, 2015). One of the major problems with TLS instruments has been the physical weight of the instrument and associated gear, making it difficult to carry further than a few hundred metres from a point of vehicle access.…”

“…Multi-temporal TLS measurements can be used to assess change over time in forest structure attributes (Calders et al, 2015a;Eitel et al, 2016;Goodwin et al, 2017;Paynter et al, 2016). However, the measurement of forest structure attributes must be able to detect "true" change, not "false" change detected from incorrect sensor settings, scanner placement or data post-processing.…”

“…In addition, portability is an important consideration for operators who must carry instruments to field plots, often over long distances or in difficult terrain (Newnham et al, 2015). The use of a highly portable and rugged instrument, which is price accessible to users, will enable a larger number of field sites to be collected when compared to manual forest inventory which is highly labour intensive (Paynter et al, 2016). The processing time required to extract structural information from TLS scans can still however be high, and to minimise this the adoption of automated processing methods is needed (the development of such methods forms part of driver for the work in this thesis).…”