Estimating Free-Flow Speed with LiDAR and Overhead Imagery

Understanding free-flow speed is fundamental to transportation engineering in order to improve traffic flow, control, and planning. The free-flow speed of a road segment is the average speed of automobiles unaffected by traffic congestion or delay. Collecting speed data across a state is both expensive and time consuming. Some approaches have been presented to estimate speed using geometric road features for certain types of roads in limited environments. However, estimating speed at state scale for varying landscapes, environments, and road qualities has been relegated to manual engineering and expensive sensor networks. This thesis proposes an automated approach for estimating free-flow speed using LiDAR (Light Detection and Ranging) point clouds and satellite imagery. Employing deep learning for high-level pattern recognition and feature extraction, we present methods for predicting free-flow speed across the state of Kentucky

Comparison of LiDAR and digital aerial photogrammetry for characterizing canopy openings in the Boreal Forest of Northern Alberta

Forest canopy openings are a key element of forest structure, influencing a host of ecological dynamics. Light detection and ranging (LiDAR) is the de-facto standard for measuring three-dimensional forest structure, but digital aerial photogrammetry (DAP) has emerged as a viable and economical alternative. We compared the performance of LiDAR and DAP data for characterizing canopy openings and no-openings across a 1-km2 expanse of boreal forest in northern Alberta, Canada. Structural openings in canopy cover were delineated using three canopy height model (CHM) alternatives, from (i) LiDAR, (ii) DAP, and (iii) a LiDAR/DAP hybrid. From a point-based detectability perspective, the LiDAR CHM produced the best results (87% overall accuracy), followed by the hybrid and DAP models (47% and 46%, respectively). The hybrid and DAP CHMs experienced large errors of omission (9–53%), particularly with small openings up to 20m2, which are an important element of boreal forest structure. By missing these, DAP and hybrid datasets substantially under-reported the total area of openings across our site (152,470 m2 and 159,848 m2, respectively) compared to LiDAR (245,920 m2). Our results illustrate DAP’s sensitivity to occlusions, mismatched tie points, and other optical challenges inherent to using structure-from-motion workflows in complex forest scenes. These under-documented constraints currently limit the technology’s capacity to fully characterize canopy structure. For now, we recommend that operational use of DAP in forests be limited to mapping large canopy openings, and area-based attributes that are well-documented in the literature

Sensing Mountains

Sensing mountains by close-range and remote techniques is a challenging task. The 4th edition of the international Innsbruck Summer School of Alpine Research 2022 – Close-range Sensing Techniques in Alpine Terrain brings together early career and experienced scientists from technical-, geo- and environmental-related research fields. The interdisciplinary setting of the summer school creates a creative space for exchanging and learning new concepts and solutions for mapping, monitoring and quantifying mountain environments under ongoing conditions of change

Assessing the cumulative impact of wildland fires and seismic line disturbance on peatlands in northern Alberta

This thesis examined the impact of wildland fires and seismic line fragmentation on peatlands in northern Alberta. The objectives were to determine if wildland fires alter regeneration trajectories of conifer vs deciduous species and lead towards the regeneration of woody vegetation adjacent to seismic lines. Multi-spectral lidar data were collected for a boreal peatland chronosequence of 5, 18, 30, and 38 years since fire (YSF) and were compared with areas that had not burned to quantify changes in the post-fire distribution of shrubs and trees. The results illustrated that there was high shrub regeneration in peatlands up to and including 38 YSF and trees tended to grow above shrubs by 18 YSF. Wildland fires promoted woody vegetation regeneration adjacent to seismic lines with taller deciduous trees and conifers found in mature post-fire peatlands (30 to 38 YSF). However, fens were more vulnerable to seismic line fragmentation and had less post-fire regeneration compared to bogs