A System for Continuous Underground Site Mapping and Exploration

3D mapping becomes ever more important not only in industrial mobile robotic applications for AGV and production vehicles but also for search and rescue scenarios. In this chapter we report on our work of mapping and exploring underground mines. Our contribution is two-fold: First, we present our custom-built 3D laser range platform SWAP and compare it against an architectural laser scanner. The advantages are that the mapping vehicle can scan in a continuous mode and does not have to do stop-and-go scanning. The second contribution is the mapping tool mapit which supports and automates the registration of large sets of point clouds. The idea behind mapit is to keep the raw point cloud data as a basis for any map generation and only store all operations executed on the point clouds. This way the initial data do not get lost, and improvements on low-level date (e.g. improved transforms through loop closure) will automatically improve the final maps. Finally, we also present methods for visualization and interactive exploration of such maps

Optimizing Scan Homogeneity for Building Full-3D Lidars based on Rotating a Multi-Beam Velodyne Rangefinder

Multi-beam lidar (MBL) scanners are compact, light, and accessible 3D sensors with high data rates, but they offer limited vertical resolution and field of view (FOV). Some recent robotics research has profited from the addition of a degree-of-freedom (DOF) to an MBL to build rotating multi-beam lidars (RMBL) that can achieve high-resolution scans with full spherical FOV. In a previous work, we offered a methodology to analyze the complex 3D scan measurement distributions produced by RMBLs with a rolling DOF and no pitching. In this paper, we investigate the effect of introducing constant pitch angles in the construction of the RMBLs with the purpose of finding a kinematic configuration that optimizes scan homogeneity with a spherical FOV. To this end, we propose a scalar index of 3D sensor homogeneity that is based on the spherical formulation of Ripley's K function. The optimization is performed for the widely used Puck (VLP-16) and HDL-32 sensors by Velodyne.This work was partially funded by the Spanish project {DPI2015-65186-R}. The publication has received support from Universidad de Málaga, Campus de Excelencia Andalucía Tech

Mobile graphics: SIGGRAPH Asia 2017 course

Peer ReviewedPostprint (published version

Unmanned Robotic Systems and Applications

This book presents recent studies of unmanned robotic systems and their applications. With its five chapters, the book brings together important contributions from renowned international researchers. Unmanned autonomous robots are ideal candidates for applications such as rescue missions, especially in areas that are difficult to access. Swarm robotics (multiple robots working together) is another exciting application of the unmanned robotics systems, for example, coordinated search by an interconnected group of moving robots for the purpose of finding a source of hazardous emissions. These robots can behave like individuals working in a group without a centralized control

Detection of Earthflow Using a GPS and LiDAR Integrated Survey: A Case Study from the Slumgullion Landslide, Lake City, Colorado

The Slumgullion landslide in the San Juan Mountains near Lake City, Colorado has been a natural laboratory for landslide and environmental studies since the early 1900s. The landslide site covers 4.6 square kilometers and consists of an active part which has been moving continuously for about 300 years over an older, much larger, inactive part. We conducted an integrated GPS and LiDAR survey at the landslide site in one-week period from July 3rd to July 10th, 2015, with the primary purpose of delineating short-term ground deformation associated with the earthflow using advanced GPS and LiDAR techniques. A GPS network with twelve semi-permanent stations was set up, including seven stations on the sliding mass and five stations outside the sliding mass. A RIEGL VZ-2000 terrestrial laser scanner was used to collect data in the field. Airborne laser scanning data were collected by the National Center for Airborne Laser Mapping. We compared different registration methods for datasets acquired by the terrestrial laser scanner. A rapid workflow for field surveying and data processing was developed to generate high-resolution digital terrain models. The movement of the Slumgullion landslide was derived from semi-permanent GPS observations, and two repeated terrestrial laser scanning surveys conducted during the one-week period. A 1.47 cm horizontal daily movement was detected from the GPS observations. We compared different change detection strategies for the LiDAR point clouds measurements. Lateral landslide movements were detected from cloud-to-cloud comparison using the data from terrestrial laser scanning; the accumulated motion ranged from 3 cm to 10 cm during the survey week. The movement measurements derived from GPS and the terrestrial laser scanner agreed well. Our study demonstrates a method of identifying slow earth mass movement using the integration of GPS, terrestrial, and airborne laser scanning datasets. We developed a workflow for terrestrial laser-scanning data processing. Our method could be applied to study landslides in other regions. It is expected that our results will promote the application of GPS and LiDAR techniques in the practice of landslide hazards mitigation.Earth and Atmospheric Sciences, Department o

Lidar SLAM-Mapping As A Potential Powerline Maintenance Tool

The purpose of this master’s thesis is to determine whether it is possible to utilize non-conventional sensory systems for power line inspection during times that more conventional methods are severely restricted. To achieve this, we will utilize lidar-generated point clouds in conjunction with measurement data from inertial measurement units to create a geo-referenced set of point clouds to generate a map of the point-of-interest area. This will be achieved by conjoining raw lidar-data from a lidar sensor and using the data provided from the inertial measurement unit to merge millions of points into a one cohesive map. We will use Robot Op-erating System to achieve the evaluation, fusion and integration of the different streams of data. We will also use Google Cartographer to aid us in the SLAM-mapping of the different sensory data sources. Once a SLAM-mapped point cloud is generated, we can evaluate the accuracy of the data and the possibilities of the generated data to be used as a maintenance tool to assist in detecting and solving various problems that many electrical companies in rural Finland face during their daily business. Such problems are snapped power lines or excess object blocking the power lines. We will want to determine if a system like this could be used when it is impossible for cameras or the naked eye of a human to detect this kind of faults, for example during the night or during a storm

Pyörivien monilaserkeilainjärjestelmien geometrinen kalibrointi

The introduction of light-weight and low-cost multi-beam laser scanners provides ample opportunities in positioning and mapping as well as automation and robotics. The fields of view (FOV) of these sensors can be further expanded by actuation, for example by rotation. These rotating multi-beam lidar (RMBL) systems can provide fast and expansive coverage of the geometries of spaces, but the nature of the sensors and their actuation leave room for improvement in accuracy and precision. Geometric calibration methods addressing this space have been proposed, and this thesis reviews a selection of these methods and evaluates their performance when applied to a set of data samples collected using a custom RMBL platform and six Velodyne multi-beam sensors (one VLP-16 Lite, four VLP-16s and one VLP-32C). The calibration algorithms under inspection are unsupervised and data-based, and they are quantitatively compared to a target-based calibration performed using a high-accuracy point cloud obtained using a terrestrial laser scanner as a reference. The data-based calibration methods are automatic plane detection and fitting, a method based on local planarity and a method based on the information-theoretic concept of information entropy. It is found that of these, the plane-fitting and entropy-based measures for point cloud quality obtain the best calibration results.Kevyet ja edulliset monilaserkeilaimet tuovat uusia mahdollisuuksia paikannus- ja kartoitusaloille mutta myös automaatioon ja robotiikkaan. Näiden sensorien näköaloja voidaan kasvattaa entisestään esimerkiksi pyörittämällä, ja näin toteutettavat pyörivät monilaserkeilainjärjestelmät tuottavat nopeasti kattavaa geometriaa niitä ympäröivistä tiloista. Sensorien rakenne ja järjestelmän liikkuvuus lisäävät kuitenkin kohinaa ja epävarmuutta mittauksissa, minkä vuoksi erilaisia geometrisia kalibrointimenetelmiä onkin ehdotettu aiemmassa tutkimuksessa. Tässä diplomityössä esitellään valikoituja kalibrointimenetelmiä ja arvioidaan niiden tuloksia koeasetelmassa, jossa pyörivälle alustalle asennetuilla Velodyne-monilaserkeilaimilla (yksi VLP-16 Lite, neljä VLP-16:aa ja yksi VLP-32C) mitataan liikuntasalin geometriaa. Tarkasteltavat menetelmät ovat valvomattomia ja vain mittauksiin perustuvia ja niitä verrataan samasta tilasta hankittuun tarkkaan maalaserkeilausaineistoon. Menetelmiä ovat tasojen automaattinen etsintä ja sovitus, paikalliseen tasomaisuuteen perustuva menetelmä sekä informaatioteoreettiseen entropiaan perustuva menetelmä. Näistä tasojen sovitus ja entropiamenetelmä saavuttivat parhaat kalibrointitulokset referenssikalibraatioon verrattaessa

Feasibility studies of terrestrial laser scanning in Coastal Geomorphology, Agronomy, and Geoarchaeology

Terrestrial laser scanning (TLS) is a newer, active method of remote sensing for the automatic detection of 3D coordinate points. This method has been developed particularly during the last 20 years, in addition to airborne and mobile laser scanning methods. All these methods use laser light and additional angle measurements for the detection of distances and directions. Thus, several thousands to hundreds of thousands of polar coordinates per second can be measured directly by an automatic deflection of laser beams. For TLS measurements, the coordinates and orientation of the origin of the laser beam can be determined to register different scan positions in a common coordinate system. These measurements are usually conducted by Global Navigation Satellite Systems or total station surveying, but also identical points can be used and data driven methods are possible. Typically, accuracies and point densities of a few centimetres to a few millimetres are achieved depending on the method. The derived 3D point clouds contain millions of points, which can be evaluated in post-processing stages by symbolic or data-driven methods. Besides the creation of digital surface and terrain models, laser scanning is used in many areas for the determination of 3D objects, distances, dimensions, and volumes. In addition, changes can be determined by multi-temporal surveys. The terrestrial laser scanner Riegl LMS Z-420i was used in this work in combination with the Differential Global Positioning System system Topcon Hiper Pro, based on Real Time Kinematic (RTK-DGPS). In addition to the direct position determination of the laser scanner, the position of a self-developed reflector on a ranging pole was measured by the RTK-DGPS system to accurately derive the orientation of each measured point cloud. Moreover, the scanner is equipped with an additional, mounted camera Nikon D200 to capture oriented pictures. These pictures allow colouring the point cloud in true colours and thus allow a better orientation. Furthermore, the pictures can be used for the extraction of detailed 3D information and for texturing the 3D objects. In one of the post-processing steps, the direct georeferencing by RTK-DGPS data was refined using the Multi Station Adjustment, which employs the Iterative Closest Point algorithm. According to the specific objectives, the point clouds were then filtered, clipped, and processed to establish 3D objects for further usage. In this dissertation, the feasibility of the method has been analysed by investigating the applicability of the system, the accuracy, and the post-processing methods by means of case studies from the research areas of coastal geomorphology, agronomy, and geoarchaeology. In general, the measurement system has been proven to be robust and suitable for field surveys in all cases. The surveys themselves, including the selected georeferencing approach, were conducted quickly and reliably. With the refinement of the Multi Station Adjustment a relative accuracy of about 1 cm has been achieved. The absolute accuracy is about 1.5 m, limited by the RTK-DGPS system, which can be enhanced through advanced techniques. Specific post-processing steps have been conducted to solve the specific goals of each research area. The method was applied for coastal geomorphological research in western Greece. This part of the study deals with 3D reconstructed volumes and corresponding masses of boulders, which have been dislocated by high energy events. The boulder masses and other parameters, such as the height and distance to the current sea level, have been used in wave transport equations for the calculation of minimum wave heights and velocities of storm and tsunami scenarios and were compared to each other. A significant increase in accuracy of 30% on average compared with the conventional method of simply measuring the axes was detected. For comparison, annual measurements at seven locations in western Greece were performed over three years (2009-2011) and changes in the sediment budget were successfully detected. The base points of the RTK-DGPS system were marked and used every year. Difficulties arose in areas with high surface roughness and slight changes in the annual position of the laser scanner led to an uneven point density and generated non-existing changes. For this reason, all results were additionally checked by pictures of the mounted camera and a direct point cloud comparison. Similarly, agricultural plants were surveyed by a multi-temporal approach on a field over two years using the stated method. Plant heights and their variability within a field were successfully determined using Crop Surface Models, which represent the top canopy. The spatial variability of plant development was compared with topographic parameters as well as soil properties and significant correlations were found. Furthermore, the method was carried out with four different types of sugar-beet at a higher resolution, which was achieved by increasing the height of the measurement position. The differences between the crop varieties and their growth behaviour under drought stress were represented by the derived plant heights and a relation to biomass and the Leaf Area Index was successfully established. With regard to geoarchaeological investigations in Jordan, Spain, and Egypt, the method was used in order to document respective sites and specific issues, such as proportions and volumes derived from the generated 3D models were solved. However, a full coverage of complexly structured sites, like caves or early settlements is partially prevented by the oversized scanner, slow measurement rates, and the necessary minimum measurement distance. The 3D data can be combined with other data for further research by the common georeference. The selected method has been found suitable to create accurate 3D point clouds and corresponding 3D models that can be used in accordance with the respective research problem. The feasibility of the TLS method for various issues of the case studies was proven, but limitations of the used system have also been detected and are described in the respective chapters. Further methods or other, newer TLS systems may be better suited for specific cases

A full 3D reconstruction of rail tracks using a camera array

This research addresses limitations found in existing 3D track reconstruction studies, which often focus solely on specific rail sections or encounter deployment challenges with rolling stock. To address this challenge, we propose an innovative solution: a rolling-stock embedded arch camera array scanning system. The system includes a semi-circumferential focusing vision array, an arch camera holder, and a Computer Numerical Control machine to simulate track traverse. We propose an optimal configuration that balances accuracy, full rail coverage, and modelling efficiency. Sensitivity analysis demonstrates a reconstruction accuracy within 0.4 mm when compared to Lidar-generated ground truth models. Two real-world experiments validate the system's effectiveness following essential data preprocessing. This integrated technique, when combined with rail rolling stocks and robotic maintenance platforms, facilitates swift, unmanned, and highly accurate track reconstruction and surveying