Heidelberg, Univ., Master-Arb., 2007.

Remotely sensing recent growth, herbivory, or disturbance of herbaceous and woody vegetation in dryland ecosystems requires high spatial resolution and multi-temporal depth. Three dimensional (3D) remote sensing technologies like lidar, and techniques like structure from motion (SfM) photogrammetry, each have strengths and weaknesses at detecting vegetation volume and extent, given the instrument's ground sample distance and ease of acquisition. Yet, a combination of platforms and techniques might provide solutions that overcome the weakness of a single platform. To explore the potential for combining platforms, we compared detection bias amongst two 3D remote sensing techniques (lidar and SfM) using three different platforms [ground-based, small unmanned aerial systems (sUAS), and manned aircraft]. We found aerial lidar to be more accurate for characterizing the bare earth (ground) in dense herbaceous vegetation than either terrestrial lidar or aerial SfM photogrammetry. Conversely, the manned aerial lidar did not detect grass and fine woody vegetation while the terrestrial lidar and high resolution near-distance (ground and sUAS) SfM photogrammetry detected these and were accurate. UAS SfM photogrammetry at lower spatial resolution under-estimated maximum heights in grass and shrubs. UAS and handheld SfM photogrammetry in near-distance high resolution collections had similar accuracy to terrestrial lidar for vegetation, but difficulty at measuring bare earth elevation beneath dense herbaceous cover. Combining point cloud data and derivatives (i.e., meshes and rasters) from two or more platforms allowed for more accurate measurement of herbaceous and woody vegetation (height and canopy cover) than any single technique alone. Availability and costs of manned aircraft lidar collection preclude high frequency repeatability but this is less limiting for terrestrial lidar, sUAS and handheld SfM. The post-processing of SfM photogrammetry data became the limiting factor at larger spatial scale and temporal repetition. Despite the utility of sUAS and handheld SfM for monitoring vegetation phenology and structure, their spatial extents are small relative to manned aircraft.

This thesis deals with creating BIM model using laser scanning. It includes information about laser scanning, BIM and proces of modelling. Result of thesis is information model created in software Revit.

This thesis has two aims. The first one is the investigation and analysis of the errors occurring in the measurements with pulsed time-of-flight (TOF) terrestrial laser scanners (TLS). A good understanding of the error sources and the relationships between them is necessary to secure the data accuracy. We subdivide these errors into four groups: instrumental, object-related, environmental and methodological. Based on our studies and the results obtained by other researchers, we have compiled an error model for TLS, which is used to estimate the single-point coordinate accuracy of a point in the point cloud, transformed to the specified coordinate system. The second aim is to investigate systematic instrumental errors and performance of three pulsed TOF laser scanners – Callidus 1.1, Leica HDS 3000 and Leica HDS 2500 – and to develop calibration procedures that can be applied by the users to determine and correct the systematic errors in these instruments. The investigations have been performed at the indoor 3D calibration field established at KTH and outdoors. The systematic instrumental errors, or calibration parameters, have been estimated in a self-calibration according to the parametric least-squares adjustment in MATLAB®. The initial assumption was that the scanner instrumental errors are similar to those in a total station. The results have shown that the total station error model is applicable for TLS as a first approximation, but additional errors, specific to the scanner design, may appear. For example, we revealed a significant vertical scale error in the scanner Callidus 1.1, caused by the faults of the angular position sensor. The coordinate precision and accuracy of the scanners, estimated during the self-calibration, is at the level of several millimetres for Callidus 1.1 and Leica HDS 3000, and at the submillimetre level for Leica HDS 2500. In other investigations, we revealed a range drift of up to 3 mm during the first few hours of scanning, presumably due to the changes in the temperature inside the scanners. The angular precision depends on the scanner design (“panoramic” or “camera-like”), and the angular accuracy depends on the significant calibration parameters in the scanner. Investigations of the influence of surface reflectance on the range measurements have shown that the indoor illumination and surface wetness have no tangible influence on the results. The type of the material does not affect, in general, the ranging precision for Callidus 1.1, but it affects the ranging precision and accuracy of the scanners Leica HDS 3000 and Leica HDS 2500. The reason may be different wavelength and, possibly, different design of the electronics in the laser rangefinders. Materials with high reflectance and those painted with bright “warning” colours may introduce significant offsets into the measured ranges (5 – 15 cm), when scanned from close ranges at normal incidence with the scanner Leica HDS 3000. “Mixed pixels” at the object edge may introduce a range error of several centimetres, on the average, depending on the type of the material. This phenomenon leads also to the distortions of the object size, which may be reduced by the removal of the “mixed pixels” based on their intensity. The laser beam intensity recorded by the scanner tends to decrease with an increased incidence angle, although not as assumed by the popular Lambertian reflectance model. Investigations of the scanner Leica HDS 2500 outdoors have revealed no significant influence of the “normal” atmospheric conditions on the range measurements at the ranges of up to 50 m. Finally, we have developed and tested two simple procedures for the calibration of the vertical scale (and vertical index) error and zero error in laser scanners. We have also proposed an approach for the evaluation of the coordinate precision and accuracy in TLS based on the experiences from airborne laser scanning (ALS). / QC 20101123

3D models have been widely used in many areas since decades ago. When BIM (Building Information Modelling) and VR (Virtual Reality) become popular recent years, 3D model, as an essential part of it has been frequently asked or even required, which is both a challenge and opportunity to a surveying engineer.   Through investigation of three different alternatives to create 3D models: image based, terrestrial laser scanning based and airborne laser scanning based modelling, the author aims to help a surveying engineer to choose the proper method and tool. Workflows, costs and applications have been discussed for each approach and the results show that image based modeling is most time and cost efficient but with lower accuracy which is suitable for visualization while thanks to the high resolution of data capture, terrestrial laser scanning based modeling can be utilized for detailed as-built modeling or BIM. The weakness of such method is the high initial cost and much time demanded; for large area city modeling, the airborne laser scanning approach is the most efficient way with limitations of the low level of details and expensive equipment.   However, it should be critical to understand that there is no automatic way to reconstruct a controllable 3D object at present. Due to the limited accessibility of equipment, the photogrammetric 3D building reconstruction method is not included in this study and thus, a future study may continue with this method. 3D object may be converted to a format that can be used in BIM, such kind of format exchange can be an interesting topic for further study.

Photogrammetry and laser scanning are remote sensing technologies with the potential to monitor movements of rock masses and their support systems in underground mine environments. Displacements underground are traditionally measured through point measurement devices, such as extensometers. These are generally restricted to measuring one dimension, may change behavior with installation, may obstruct mining operations, and are restricted to monitoring the behavior of a small area. Photogrammetry and laser scanning offer the ability to monitor rock mass movements at millions of points in a local area, both accurately and quickly. An improved, or augmented, method for measuring displacements underground in a practical, cost-effective manner will lead to an improved understanding of rock mass behavior. Several experiments were performed that demonstrate the applicability of these remote sensing techniques to monitoring rock mass changes. An underground mining environment presents unique challenges to using these tools for monitoring rock movements, such as: poor lighting, dust, fog, and unfavorable geometries. It is important, therefore, to demonstrate that these tools which have applications in other industries, can also be adapted to the conditions of an underground mine. The study sites chosen include two different underground limestone mines, two different underground coal mines, and the Mine Roof Simulator (MRS) at the Pittsburgh Office of Mine Safety and Health Research. Both photogrammetry and laser scanning were tested at different limestone mines to detect scaling and spalling on ribs that occurred over several weeks. Both methods were successfully used to reconstruct three-dimensional models of the limestone ribs and detect areas of rock change between visits. By comparing the reconstructed point clouds, and the triangulated meshes created from them, volumes of rock change could be quantified. The laser scanned limestone mine showed a volume of 2.3 m3 and 2.6 m3 being displaced across two ribs between visits. The photogrammetry study involved seven different pillars and at least one rib face modeled on each, with volume changes of 0.29 to 4.03 m3 detected between visits. The rock displaced from the ribs could not be measured independently of the remote sensing, but a uniform absence of rock movement across large areas of the mine validates the accuracy of the point clouds. A similar test was performed using laser scanning in an underground coal mine, where the displacement was induced by removing material by hand from the ribs. Volume changes as small as 57 cm3, or slightly larger than a golf ball, and as large as 57,549 cm3, were detectable in this environment, despite the change in rib surface reflectance and mine geometry. In addition to the rib displacement, photogrammetry was selected as a tool for monitoring standing supports in underground coal mines. The additional regulatory restrictions of underground coal may preclude the use of laser scanning in these mines where deformation is most likely to occur. The camera used for photogrammetry is ATEX certified as explosion proof and is indicative of the specifications that could be expected in an MSHA approved camera. Three different experiments were performed with this camera, including a laboratory controlled standing support deformation at the MRS and an in-mine time-lapse experiment measuring the response of a wooden crib and steel support to abutment loading. The experiment reconstructing a standing support in the MRS showed a cumulative convergence of 30.93 cm through photogrammetry and 30.48 cm as measured by the system. The standing support monitoring in the underground coal mine environment showed a steel support cumulative convergence of 1.10 cm, a wooden crib cumulative convergence of 0.62 cm, and a measured cumulative convergence on the wooden crib of 0.62 cm. These techniques explored in this report are not intended to supplant, but rather supplement, existing measurement technologies. Both laser scanning and photogrammetry have physical and regulatory limitations in their application to measuring underground mine deformations, however, their ability to provide time-lapse three-dimensional measurements of entire mine sections is a strength difficult to emulate with traditional point measurement techniques. A fast, cost-effective, and practical application of remote sensing to monitoring mine displacements will improve awareness and understanding of rock mass behavior. / Ph. D.

Three-dimensional laser scanning has revolutionized spatial data acquisition and can be completed from a variety of platforms including airborne (ALS), mobile (MLS), and static terrestrial (TLS) laser scanning. MLS is a rapidly evolving technology that provides increases in efficiency and safety over static TLS, while still providing similar levels of accuracy and resolution. The componentry that make up a MLS system are more parallel to Airborne Laser Scanning (ALS) than to that of TLS. However, achievable accuracies, precisions, and resolution results are not clearly defined for MLS systems. As such, industry professionals need guidelines to standardize the process of data collection, processing, and reporting. This thesis lays the foundation for MLS guidelines with a thorough review of currently available literature that has been completed in order to demonstrate the capabilities and limitations of a generic MLS system. A key difference between MLS and TLS is that a mobile platform is able to collect a continuous path of geo-referenced points along the navigation path, while a TLS collects points from many separate reference frames as the scanner is moved from location to location. Each individual TLS setup must be registered (linked with a common coordinate system) to adjoining scan setups. A study was completed comparing common methods of TLS registration and geo-referencing (e.g., target, cloud-cloud, and hybrid methods) to assist a TLS surveyor in deciding the most appropriate method for their projects. Results provide insight into the level of accuracy (mm to cm level) that can be achieved using the various methods as well as the field collection and office processing time required to obtain a fully geo-referenced point cloud. Lastly, a quality assurance methodology has been developed for any form of LiDAR data to verify both the absolute and relative accuracy of a point cloud without the use of retro-reflective targets. This methodology incorporates total station validation of a scanners point cloud to compare slopes of common features. The comparison of 2D slope features across a complex geometry of cross-sections provides 3D positional error in both horizontal and vertical component. This methodology lowers the uncertainty of single point accuracy statistics for point clouds by utilizing a larger portion of a point cloud for statistical accuracy verification. This use of physical features for accuracy validation is particularly important for MLS systems because MLS systems cannot produce sufficient resolution on targets for accuracy validation unless they are placed close to the vehicle. / Graduation date: 2012

The implementation of Unmanned Aerial Vehicles (UAVs) and Structure‐from‐Motion (SfM) photogrammetry in assessing forest structures for forest inventory and biomass estimations has shown great promise in reducing costs and labour intensity while providing relative accuracy. Tree Height (TH) and Diameter at Breast Height (DBH) are two major variables in biomass assessment. UAV-based TH estimations depend on reliable Digital Terrain Models (DTMs), while UAV-based DBH estimations depend on reliable dense photogrammetric point cloud. The main aim of this study was to evaluate the performance of multirotor UAV photogrammetric point cloud in estimating homogeneous and heterogeneous forest structures, and their comparison to more accurate LiDAR data obtained from Aerial Laser Scanners (ALS), Terrestrial Laser Scanners (TLS), and more conventional means like manual field measurements. TH was assessed using UAVSfM and LiDAR point cloud derived DTMs, while DBH was assessed by comparing UAVSfM photogrammetric point cloud to LiDAR point cloud, as well as to manual measurements. The results obtained in the study indicated that there was a high correlation between UAVSfM TH and ALSLiDAR TH (R2 = 0.9258) for homogeneous forest structures, while a lower correlation between UAVSfM TH and TLSLiDAR TH (R2 = 0.8614) and UAVSfM TH and ALSLiDAR TH (R2 = 0.8850) was achieved for heterogeneous forest structures. A moderate correlation was obtained between UAVSfM DBH and field measurements (R2 = 0.5955) for homogenous forest structures, as well as between UAVSfM DBH and TLSLiDAR DBH (R2 = 0.5237), but a low correlation between UAVSfM DBH and UAVLiDAR DBH (R2 = 0.1114). This research has demonstrated that UAVSfM can be adequately used as a cheaper alternative in forestry management compared to more highcost and accurate LiDAR, as well as traditional technologies, depending on accuracy requirements.

Mounting evidence suggests that tree species richness promotes ecosystem functioning in forests. However, the mechanisms driving positive biodiversity ecosystem functioning relationships remain largely unclear. This also holds for the previously proposed key mechanisms of resource partitioning in canopy space. Until recently, surveying and hence the study of crown space was very time-consuming and the images low resolution. The application of high-resolution laser scanning, however, now enables a fast and precise recording of entire forests. This thesis presents how the abandonment of management strongly alters the individual tree structure from the wood distribution along the trunk to the crown, a tree species-rich neighbourhood can increase the wood volume and crown dimension of individual trees as well as the productivity of large-sized trees, mobile laser scanning in forests is suitable for the acquisition of high-quality point clouds and determination of relevant management parameters, and the direction and strength of the relationship between tree species richness and canopy occupation depends on the definition of both canopy and species richness. These results reinforce the influence of species richness on ecosystem functions in oldgrowth forests and underline the importance of laser scanning for forest ecology research. The findings of the comparative analyses further highlight the importance of underlying definitions for the results obtained.

Oberflächennahe Prozesse werden durch die dynamischen Eigenschaften der Bodenoberfläche besonders beeinflusst. Zwar sind die kausalen Zusammenhänge dieser Prozesse weitestgehend bekannt, doch gibt es einen Mangel an verfügbaren Datenquellen und Erhebungsmethoden, die es erlauben, die Prozesse auf unterschiedlichen Skalen zu quantifizieren. Das Ziel dieser Arbeit bestand darin, das Potential ausgewählter moderner Fernerkundungstechnologien zu bewerten, relevante Bodeneigenschaften zu quantifizieren und damit das Verständnis von oberflächennahen Prozessen in degradierten Landschaften zu verbessern. Das Studiengebiet befand sich in einer Rekultivierunglandschaft des Niederlausitzer Braunkohletagebaus Welzow-Süd. Die Größe von 4 ha ermöglichte eine umfassende, interdisziplinäre und multi-temporale Analyse der Bodeneigenschaften auf Grundlage von Fernerkundungsmethoden sowie hydrologischen und bodenkundlichen Feld- und Labormessungen. Die Quantifizierung der Bodenfeuchte als eine entscheidende Variable für Infiltrations- und Abflussprozesse war das Ziel von labor- und feldspektroskopischen Messungen sowie von hyperspektralen Flugzeugscanner-Messungen. Der hierbei entwickelte Normalized Soil Moisture Index (NSMI) wurde als optimales Quantifizierungsmodell für Oberflächen-Bodenfeuchte im Feld ermittelt. Bodenrauhigkeit wurde in hoher Präzision durch Anwendung eines stationären Laserscanners gemessen und in Form neuartiger multi-skalarer Indizes quantifiziert. Die Analyse der raum-zeitlichen Verteilungen ermöglichte die Identifizierung von Rauhigkeitsmustern, die unter dem Einfluss der Erosion im Feld entstanden. Diese Arbeit entwickelte neuartige Methoden und Indizes zur Quantifizierung von Oberflächen-Bodenfeuchte und Rauhigkeit im Feld. Für die Zukunft verspricht deren Anwendung die Entwicklung eines tieferen Verständnisses von Bodenerosionsprozessen sowie die Sammlung wertvoller Daten durch Monitoring- und Modellierungskampagnen. / Soil processes taking place in the context of erosion and land degradation are highly dependent on the properties of the surface. While the causes and effects of such processes are commonly well understood on a conceptual level, there is a lack of adequate data sources allowing for their quantification at various spatial scales. The main goal of this thesis was to assess the role of state-of-the-art remote sensing methods for the quantification of soil properties with the aim to improve the understanding of surface processes taking place in a degraded landscape. The chosen study area of 4 ha size located in a lignite mine in eastern Germany allowed for a comprehensive, interdisciplinary and multi-temporal analysis of surface properties based on remote sensing, pedological and hydrological measurements. The quantification of surface soil moisture as an important variable for infiltration and runoff processes has been the objective in laboratory and field spectroscopic experiments as well as in airborne hyperspectral measurements. The newly developed Normalized Soil Moisture Index (NSMI) was identified as the most robust quantifier for surface soil moisture in the field. Surface roughness was successfully quantified at high precision in form of novel multiscale indices derived from datasets collected with a stationary laser scanning device. The analysis of spatiotemporal roughness distributions allowed for the detection of distinct patterns that developed under the influence of soil erosion in the field. The thesis developed a set of methods and indices that successfully implement the quantification of surface soil moisture and roughness in the field. For the future, the application of these methods promises further insights into the details of soil erosion processes taking place as well as the collection of invaluable datasets to be used for soil erosion monitoring and modeling campaigns.