Browsing by Author "Lichti, Derek"
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- ItemOpen Access2D-3D Registration for a High-speed Biplanar Videoradiography Imaging System(2022-04) Zhang, Shu; Lichti, Derek; Detchev, Ivan; Ronsky, Janet; Wang, Ruisheng; Armenakis, Costas; Lichti, DerekHigh-Speed Biplanar Videoradiography (HSBV) is an X-ray based imaging system that can derive dynamic bony translations and rotations. The 2D-3D registration process matches a 3D bone model acquired from magnetic resonance imaging (MRI) or computed tomography (CT) scans with the 2D X-ray image pairs. 2D-3D registration is usually conducted in two ways, marker-based and model-based registration. The marker-based method is known for its high registration accuracy thanks to corresponding marker pairs. On the other hand, the model-based method avoids the implantation of radiopaque beads but uses the radiograph’s features, intensities, or gradients to accomplish the data alignment. Two novel marker-based registration methods, the back-projection and the projection methods, were proposed and compared with the state-of-the-art RSA (Roentgen Stereophotogrammetric Analysis) method. A 3D printed bone model with beads was used to validate the proposed methods. The results showed that both methods acquired higher accuracy than the RSA method. In addition, the projection and back-projection techniques can be used for the model-based registration while the RSA method cannot. The projection method was applied to a model-based registration to achieve higher accuracy, providing a 3D reconstruction accuracy of 0.79 mm for both the tibia and femur. By using the non-rigid transformation with a scale factor, this accuracy was successfully increased to 0.56 mm for the tibia and 0.64 mm for the femur. The discrepancies in the 2D-3D registration that led to the non-rigid transformation were validated. It was caused by the offset between the detected edge points in the radiographs and their actual position. A Kalman filter was tested on the marker- and model-based registration results with different random processes and parameters. For marker-based registrations, the standard deviations of the kinematics parameters were improved by 25 – 62% for the translations and 35 – 43% for the rotations. For the model-based registration, these standard deviations were improved by 6 – 38% and 29 – 38%, respectively. While the projection method provided higher accuracy, the back-projection method had the larger capture range for the initialization. An automatic initialization method with 64 starting poses based on the back-projection method was proposed and validated. It successfully eliminated the user intervention in the registration initialization. The improved 2D-3D registration with non-rigid transformation and dynamic estimation allows the determination of accurate 3D kinematic parameters with high efficiency. These kinematic parameters can be used to calculate joint cartilage contact mechanics that provide insight into the mechanical processes and mechanisms of joint degeneration or pathology.
- ItemOpen AccessA Geospatial Infrastructure to Collect, Evaluate, and Distribute Volunteered Geographic Information for Disaster Management(2016) Poorazizi, Mohammad Ebrahim; Lichti, Derek; Liang, Steve; Wang, Xin; Jacobson, Daniel; Kalantari, MohsenRecent disasters, such as the 2010 Haiti earthquake, have drawn attention to the potential role of citizens as active information producers. By using location-aware devices such as smartphones to collect geographic information in the form of geo-tagged text, photos, or videos, and sharing this information through online social media, such as Twitter, citizens create Volunteered Geographic Information (VGI). This thesis presents a framework for the effective use of VGI in disaster management platforms. The proposed framework consists of four components: (i) a VGI brokering module, to provide a standard service interface to retrieve VGI from multiple social media streams, (ii) a VGI quality control component, to evaluate spatiotemporal relevance and credibility of VGI, (iii) a VGI publisher module, which uses a service-based delivery mechanism to disseminate VGI, and (iv) a VGI discovery component, which acts like a yellow-pages service to find, browse, and query available VGI datasets. A set of quality metrics specifically designed for VGI evaluation is introduced. This research also presents a prototype implementation including an evaluation with social media data collected during Typhoon Hagupit (i.e., Typhoon Ruby), which hit the Philippines during December 2014. The evaluation results suggest that the proposed framework provides a promising solution towards an effective use of VGI in disaster management platforms. Utilization of the proposed quality metrics on the collected VGI database – with multiple social media stream contributions – will allow disaster response teams to make informed decisions that could save lives, meet basic humanitarian needs earlier, and perhaps limit environmental and economic damage.
- ItemOpen AccessAdvancing Arctic coastal erosion measurement and monitoring through UAV-SfM, satellite imagery, and object-based image analysis(2024-01-25) Clark, Andrew; Moorman, Brian; Bender, Darren; McDermid, Greg; Lichti, Derek; Duguay, ClaudeArctic coasts are vast, representing 30-34% of Earth’s coastline and exhibit some of the highest rates of erosion in the World due to the presence of permafrost. Rates of erosion are expected to increase with warming air and water temperatures, reductions in Arctic sea ice extent and duration, sea level rise, and increased storm severity and frequency. Erosion of Arctic coasts can lead to rapid land loss threatening habitat, archaeologically significant sites, modern infrastructure, and communities. Rapid erosion and permafrost degradation also leads to the liberation of previously frozen sediment and organic carbon into the nearshore zone which affects marine ecosystems and contributes to ocean acidification. Further, the release of organic carbon from frozen sediment contribute to global greenhouse gas release which are not well understood nor included in current Earth System Models. This thesis focuses on the use of emerging technologies to further our understanding of Arctic coastal processes, specifically, volumetric erosion, and broad scale delineation of multiple shoreline proxies for monitoring and quantification of erosion. UAV-SfM provides aerial and DSM imagery at unprecedented spatial and temporal resolution that provides perspectives and quantitative measures that are unachievable using conventional methods and very high resolution satellite imagery enables broader scale multiple proxy analysis while image classifications derived from OBIA, or GEOBIA, provide opportunities to systematically create boundary features (i.e. shoreline proxies). Overall, this doctoral research develops and evaluates techniques that enhance our ability to make quantitative measures of Arctic coastal erosion, both planimetric and volumetric, that have implications locally, regionally, and globally.
- ItemOpen AccessAssessment and attenuation of movement disorder motion using inertial sensors(2011) Teskey, Wesley; El-Sheimy, Naser; Lichti, Derek
- ItemOpen AccessAutomated Recognition of Electrical Substation Components from 3D LiDAR Point Clouds(2017) Arastounia, Mostafa; Lichti, Derek; Hassan, Quazi; Wang, RuishengThis study presents an innovative automated methodology for identification of electrical substations’ key elements from 3D LiDAR point clouds acquired by terrestrial laser scanners. The developed methodology is composed of nine algorithms that identify objects of interest with respect to their physical shape and topological relationships among them. The objects of interest in this contribution are ground, fence, cables, circuit breakers, bushings, bus pipes, insulators, and three types of poles with circular, octagonal, and square cross sectional shape. The developed methodology incorporates a computationally-efficient algorithm for detection of ground within electrical substations; two separate algorithms for identifying well-sampled and poorly-sampled fences; robust algorithms for detecting cables, circuit breakers, and bushings with respect to their unique physical shape and the topological relationships among them; and a novel method for simultaneous identification, modeling, and registration-refinement of poles with circular and regular polygonal cross sectional shapes. The proposed methods in this study work quite robustly despite the challenges introduced by non-uniform point sampling, registration error, occlusion, attached objects, gap, dense configuration of neighboring objects, and outliers. Five datasets with quite different volume and configuration were employed in this work. The first three datasets contain point clouds of two different electrical substations. The fourth and fifth datasets contain point clouds of an urban roadway and a pole-like monument with a regular dodecagonal cross section, respectively. The obtained results indicate that 367 out of 382 objects of interest (96.1%) in the first dataset; 354 out of 382 objects of interest (92.7%) in the second dataset; and 255 out of 264 objects of interest (96.6%) in the third dataset were successfully recognized. At point cloud level, it achieved greater than 99%, 96%, and 97% average recognition precision and accuracy in the first, second, and third dataset, respectively. Furthermore, the poles in the fourth and fifth datasets were successfully identified and the registration-refined version and as-built model of poles in all five datasets were automatically generated. The center and size standard deviation of the constructed models was less than 3 mm and the rotation angle standard deviation was less than 0.3° for all identified poles.
- ItemOpen AccessCalibration, Validation, and Verification of Static Terrestrial Laser Scanning for Professional Land Surveying of 3D Boundaries(2017) Rondeel, Samuel; Barry, Michael; Lichti, Derek; Wang, Xin; Collins, MichaelThis thesis examines the validity of static terrestrial laser scanning self-calibration and measurement procedures within current 3D cadastral surveying law in Canada, Australia and South Africa. It examines methodologies used to validate static terrestrial laser scanning outputs subjected to rigorous cross-examination within professional land surveying missions. Due to the construction and design of current laser scanning systems, the raw measurements are not typically available for analysis by the operator and thus their validity could be scrutinized in a court of law. The objectives are met by reviewing and analyzing typical terrestrial laser scanner measurements and outputs based on the laser scanning system construction, scanning environment, and scanning mission procedures. The results show that while terrestrial laser scanning systems provide invaluable information, they could be scrutinized if the proper procedures are not followed. However, the results also suggest that the complimentary methods of terrestrial laser scanning and total station measurements provide the most rigorous results when defining 3D boundaries.
- ItemOpen AccessCondition Monitoring of Wind Turbine Blades(2018-03-01) Sanati, Hadi; Wood, David; Sun, Qiao; Lichti, Derek; Hugo, Ron; Korobenko, ArtemThe failure of wind turbine blades is a major concern in the wind power industry due to the resulting high cost. Leading-edge erosion is another issue of blades which may affect their performance and result in energy loss. It is therefore crucial to develop methods to improve the integrity of wind turbine blades and to detect surface and subsurface defects before they can result in blade failure. This research employed laser scanning to reconstruct the surface of the blade to measure leading-edge erosion. Computational Fluid Dynamics simulations were used to determine the deterioration of aerodynamic characteristics resulting from leading-edge erosion. The results suggest that it is possible to successfully evaluate the aerodynamic characteristics of eroded and clean airfoils. Different methods are available to detect subsurface damage in blades but most require close proximity between the sensor and the blade. To address this limitation, the use of thermography as a non-contact method was developed in this study. Both passive and active thermography techniques were investigated for different purposes. Passive thermography can be used to detect internal defects on an operating blade, whereas active thermography is restricted to pre-delivery blade inspection and site inspections when the blades are removed from the turbine. Pulsed and step heating as active thermography methods were studied. The raw thermal images captured by both active and passive thermography demonstrated that image processing was required to improve the quality of thermal data. Different image processing algorithms, including Thermal Signal Reconstruction, Principal Component Thermography, Matched Filters, and Pulsed Phase Thermography, were used to increase the thermal contrasts of subsurface defects in thermal images obtained by active thermography. A method called “Step Heating Phase and Amplitude Thermography”, which applies a transform-based algorithm on step heating data, was developed. This method was also applied to passive thermography results. The outcomes of image processing on both active and passive thermography indicated that the techniques employed could considerably increase the quality of the images and the visibility of internal defects.
- ItemOpen AccessCorrection of Motion Artifacts in Whole Heart Optical Mapping Data Using Ratiometry and Image Processing Techniques(2015-12-22) Rodriguez Ramirez, Marcela Patricia; Nygren, Anders; Lichti, Derek; Murari, Kartikeya; Duncan, Neil; Oudit, GavinCardiac optical mapping is a powerful tool to understand the electrophysiological mechanisms responsible for normal and abnormal cardiac rhythm. However, motion artifacts contained in the optical action potentials (APs) represent a major drawback of the technique. The calculation of electrophysiological parameters of interest such as action potential duration (APD) is challenged by the presence of motion artifacts. The use of chemical motion blockers is currently a preferable method to control motion artifacts, however these may affect the cardiac electrophysiology and consensus regarding their effects has not been reached. This thesis presents several key developments in techniques for motion artifact correction. Weighted ratiometry was implemented aiming to reduce motion artifacts in dual wavelength recordings. This thesis reports differences in shape and amplitude between motion artifacts contained in corresponding APs at both wavelengths. A new mathematical representation for motion artifacts is also presented to model such differences. Gross motion artifacts due to misalignment of the preparation with the imaging sensor across time are the result of the mechanical contraction of the heart. Landmark-based image registration is introduced to correct for such artifacts. It was concluded that the use of scale invariant feature transform (SIFT) is preferable for the datasets presented among the techniques evaluated for motion estimation. Several landmark-based non-rigid registration methods are studied in this thesis and their performance compared; coherence point drift (CPD) algorithms performed better for this application. Image registration resulted in good correction of gross motion artifacts, however artifacts with other origins must be handled separately. The combination of weighted ratiometry and landmark-based non-rigid registration is also evaluated as a composite method to further reduce artifacts that the techniques were not able to correct individually. The technique produced good correction and APDs calculated from the corrected datasets present low error values compared to a gold standard. APD modulation with 4-Aminopyridine served as a tool to corroborate that the combination of weighted ratiometry and image registration is able to reduce motion artifacts in APs to the point where APD can be calculated and the modulation of APD quantified.
- ItemOpen AccessCylindrical and Polygonal Object Modelling and its use in LiDAR Calibration and Point Cloud Registration(2015-01-30) Chan, Ting On; Lichti, DerekLiDAR systems are optical metrological instruments that capture surfaces of objects as highly redundant sets of discrete points (known as point clouds) in a 3D coordinate system from which spatial information can be extracted to support many applications. The accuracy of the LiDAR measurements can be improved by performing appropriate calibration. In this thesis, two novel cylinder-based calibration methods are presented for recovering interior systematic errors of different types of the LiDAR systems. The first method is a cylinder-based self-calibration technique which primarily uses point clouds of vertical cylindrical features captured from several static scan locations. The method is suitable for LiDAR systems with time-invariant errors. The second calibration method is for multi-beam spinning LiDAR systems. It allows frequent, repeated calibrations to be performed in either static or kinematic scanning mode for recovering the time-varying interior errors. For the calibration in kinematic mode, roadside power and lamp poles are used as the calibration references. In addition to these, a new geometric model of octagonal lamp poles along with a new model-driven point cloud registration method is proposed. The new geometric model uses the rotational symmetry property of the polygon to overcome the challenges of modelling the polygonal periphery using a single equation instead of piecewise functions. The proposed registration method is based on the model and requires only point clouds of a single octagonal lamp pole as registration primitives, and no actual overlap between the point clouds of the pole captured at different scan locations is needed. Each proposed method was individually verified with several real datasets, and most of them were also tested with some simulated datasets. The results suggest that all the proposed methods are practical and also offer improvements compared to the existing methods. The main contribution of this work is that many cylindrical and polygonal objects already exist in the built environment can now be used for sensor calibration, point cloud registration, and some other potential new applications as discussed in the last chapter of this thesis.
- ItemOpen AccessDetecting and Monitoring Change to an Arctic Heritage Site Using UAV Photogrammetry: A Case Study From Qikiqtaruk / Herschel Island, YT(2022-04) O'Keefe, Katelyn; Dawson, Peter C.; Oetelaar, Gerald A.; Lichti, DerekArctic heritage sites are increasingly at risk due to modern climate change. Traditional documentation and monitoring of valuable heritage resources are time-consuming. In recent years, UAV (drone) photogrammetry has become a powerful tool for visualizing heritage sites. This research goes beyond visualization by evaluating the suitability of UAV data, acquired for documenting heritage resources, and for other reasons, to perform change detection analysis on Arctic cultural landscapes. The procedures developed throughout this research can also be used to create a heritage monitoring strategy. The case study used in this research is Simpson Point on Qikiqtaruk (Herschel Island), the most western Canadian Arctic island and the only island on the Yukon coast. Within Herschel Island – Qikiqtaruk Territorial Park, the heritage resources represent 800 years of continuous occupation by Inuvialuit, their ancestors, the Thule, and Euro-North Americans. UAV imagery of Simpson Point from July 2017 and 2019 was processed using photogrammetric software. The outputs (orthomosaics and point clouds) were prepared prior to employing two highly compatible change detection methods. The results of the change detection analysis were used to explore short-term change to the heritage features and the landscape, some of which are the result of climate change-induced overland flooding and coastal erosion. Other changes required confirmation from heritage restoration personnel. The framework of a heritage monitoring strategy for the territorial park, improvements to the future UAV data collection strategy, and the advantages and disadvantages of the change detection methods used are discussed. In addition, an emphasis is placed on the importance of data sharing, the reuse of found data, and the long-term curation of digital data.
- ItemOpen AccessDetection of Road Furniture from Mobile Terrestrial Laser Scanning Point Clouds(2013-03-07) IBRAHIM, SHERIF; Lichti, DerekThere is an increased utilization of the mobile terrestrial laser scanning (MTLS) systems in different road corridor applications. These systems are fast and accurate; allowing very high density point clouds to be acquired. But their use is still limited due to their cost and the huge amount of data they capture. Processing that huge amount of data is extremely labor intensive, time consuming and requires a lot of manual processing. The aim of this research are to automatically detect different road furniture such as poles, curb and the street floor. This will be done by developing new methods for the automated segmentation of those features from a 3D point cloud captured by a MTLS system. Automating the analysis of the data reduces human bias, and both the field scanning and the point cloud processing can be conducted more rapidly. The MTLS systems are expensive, but normally the cost of utilizing them and the point cloud processing software is less expensive than the equivalent analysis using traditional methods like utilizing the Total Station and GPS. Automatically identifying the road poles from the MTLS point cloud is very important and will make the detection of the attached objects easier. The road curb and the street floor represent very important road furniture. The curb separates the street floor and side walk; it is also used to direct rainwater into the drainage system. The automatic detection of curb points from the MTLS point clouds helps in defining the road boundaries and the curb condition. Automatically detecting a highly detailed street floor helps in maintaining the pavement by estimating the road surface conditions. The location of bumps and dips can be detected to estimate the roughness of the road surface. In this research different point cloud processing pipelines have been proposed and implemented. These pipelines have successively detected the road poles, the road curb and the street floor from different MTLS point cloud scenes. The detection is done just based on the input 3D point cloud and without utilizing any additional data source. Four different point cloud datasets have been tested with the proposed methodologies. These datasets were captured by the TITAN MTLS system. The datasets represent different road scenes, like downtown and highway areas. They have different point cloud densities and side objects. These varieties enable testing the performance of the proposed methodologies. The results show the efficiency of the different point cloud processing pipelines and its applicability with different road scenes. Also, the proposed curb and street floor detection pipelines do not require any additional information about the road, like its geometry and direction. This additional information need other data sources such as the trajectory of the scanning system, aerial image or a map. The main contribution of this research is to automate most of the processing steps of the point cloud captured by MTLS systems. Automating the detection of different road furniture like the poles, the curb and the street floor is important step in order to get the full benefits of the MTLS systems. This is done through developing a new point cloud processing pipelines which are applicable to be utilized on different scenes, and automatically setting most of the thresholds for the utilized detection parameters.
- ItemOpen AccessDevelopment of an Automated Monitoring and Control System for Construction Projects(2017) Maalek, Reza; Ruwanpura, Janaka; Lichti, Derek; El-Sheimy, Naser; Jergeas, George; Fapojuwo, Abraham; Jaselskis, EdwardConstruction project progress monitoring and structural dimensional compliance control are essential for decision makers to identify discrepancies between the planned and the as-built states of a project, and take timely measures where required. In practice, monitoring is performed manually, a time consuming, error-prone and labour intensive task, particularly in large scale projects. Thus, large projects are monitored unsystematically by collecting limited onsite data, restricting the project management team to identify delays, and rework on time. The correct determination of the project’s performance also relies heavily on the correctness and completeness of the collected data during the monitoring process. Hence, site supervisory personnel spend considerable time just to manually control the quality of the manually collected onsite data. Several research studies have aimed to use remote sensing technologies such as LiDAR and cameras to acquire 3D point clouds of building elements to improve the quality of the collected data; however, these studies assume the planned BIM as a priori knowledge to assign the point clouds to their corresponding structural element, which provide inaccurate basis for reporting the as-built status of a project, especially when the planned and the actual differ or the planned model is not available with sufficient detail. Here, using the most up-to-date pattern recognition, robust statistical analysis and mathematical modelling techniques, a new robust approach was formulated, independent from a pre-existing planned model, to automatically generate the as-built model of common structural elements with predominantly planar and linear surfaces directly from the acquired point cloud. In the context of four experiments, ten sets of point clouds, nine from actual construction sites, were collected to express, verify and validate the diverse applicability of the proposed system for automated progress monitoring, structural displacement analysis, and dimensional conformation control. It was demonstrated that the novel robust planar and linear point cloud classification and segmentation method, presented here, achieved an overall accuracy of better than 90.4% for all datasets, indicating its generic applicability for construction projects. It was also shown that the proposed system is capable of automatically generating as-built models of common structural elements with the 3-5mm desired construction grade accuracy.
- ItemOpen AccessDynamic In-Vivo Knee Cartilage Contact With Aging(2020-07-27) Kupper, Jessica C.; Ronsky, Janet L.; Boyd, Steven K.; Lichti, Derek; Edwards, W. Brent; Rainbow, MichaelJoint contact mechanics are important to the study of cartilage health and disease. Risk factors such as aging are speculated to result in altered cartilage contact locations, magnitudes, and sliding velocities, leading to altered loading of typical cartilage contact and non-contact areas. Altered contact patterns are speculated to be an influential mechanism associated with osteoarthritis-related cartilage changes such as softening, stiffening, or swelling. It is unknown whether knee joint contact patterns differ in an asymptomatic aging population compared to their younger counterparts.This feasibility study aimed to enhance understanding of relations amongst contact mechanics, cartilage health, and functional status and aging. This work applied high-speed biplanar videoradiography and magnetic resonance imaging to non-invasively measure a weighted centroid (WC) of tibiofemoral cartilage contact during gait in participants between the ages of 20-30 years (n = 5), and 50-60 years (n = 5). Cartilage contact regions during walking were linked to cartilage-health imaging outcomes (i.e., T2 relaxometry).Assessment of techniques for calculating the WC revealed that interval-based weighting factors provided the optimal approach, showing low sensitivity to errors but high sensitivity to clinically relevant changes. In aging vs. younger participants, no significant differences were found in WC location (median difference between heel strike and first force peak of gait cycle: younger 5.21-9.69%, older 2.12-7.44%), sliding distance (at onset of terminal swing: younger 0.50-1.15 mm, older 0.74-1.84 mm), or phase plot slope (change in sliding velocity over the surface of the joint; for swing phase: younger 4.14-14.99 mm/s%, older 6.15-14.47 mm/s%). For the first time, a functional relationship was found between T2 relaxometry and the gait cycle with lower T2 values during stance compared to prior to terminal swing. No differences were detected (younger vs. older) in T2 relaxometry values (medial tibial compartment at first force peak of gait: younger 29.8-43.1 ms, older 31.0-37.6 ms). These findings could not support differences in contact mechanics in older asymptomatic tibiofemoral joints compared to younger joints. Nevertheless, some potentially atypical patterns in older participants provide motivation to better understand linkages amongst aging, contact mechanics and cartilage health status across the cartilage degeneration spectrum.
- ItemOpen AccessDynamic Structural Deflection Measurement with Range Cameras(2013-05-01) Qi, Xiaojuan; Lichti, DerekConcrete beams are used to construct bridges and other structures. Years of traffic overloading and insufficient maintenance have left civil infrastructure such as bridges in a poor state of repair. Therefore, the structures have to be strengthened. Many options for the reinforcement exist such as fibre-reinforced polymer composites and steel plates can be added. The efficacy of such methods can be effectively evaluated through fatigue load testing in which cyclic loads are applied to an individual structural member under laboratory conditions. During the fatigue test, the deflection of concrete beam is very important parameter to evaluate the concrete beam. This testing requires the measurement of deflection in response to the applied loads. Many imaging techniques such as digital cameras, laser scanners and range cameras have been proven to be accurate and cost-effective methods for large-area measurement of deflection under static loading conditions. However, in order to obtain useful information about behaviour of the beams or monitoring real-time bridge deflection, the ability to measure deflection under dynamic loading conditions is also necessary. This thesis presents a relatively low-cost and high accuracy imaging technique to measure the deflection of concrete beams in response to dynamic loading with different range cameras such as time-of-flight range cameras and light coded range cameras. Due to the time-of-flight measurement principle, even though target movement could lead to motion artefacts that degrade range measurement accuracy, the appropriate sampling frequency can be used to compensate the motion artefacts. The results of simulated and real-data investigation into the motion artefacts show that the lower sampling frequency results in the more significant motion artefact. The results from the data analysis of the deflection measurement derived from time-of-fight range cameras have been indicated that periodic deflection can be recovered with half-millimetre accuracy at 1 Hz and 3 Hz target motion. A preliminary analysis for light coded range cameras is conducted on dynamic deflection measurement. The results demonstrate that the depth measurements of Kinect light coded range cameras are unstable, which implied that it is not sufficient to meet the accuracy required for the dynamic structural deflection measurement.
- ItemOpen AccessFeature-based boresight self-calibration of a mobile mapping system(2011) Chan, Ting On; Lichti, Derek
- ItemOpen AccessGeometric modelling of 3d range cameras and their application for structural deformation measurement(2010) Jamtsho, Sonam; Lichti, Derek
- ItemOpen AccessImage-based Fine-scale Infrastructure Monitoring(2016) Detchev, Ivan; Habib, Ayman; Lichti, Derek; El-Badry, Mamdouh; El-Sheimy, Naser; Sadeghpour, Farnaz; Sohn, GunhoMonitoring the physical health of civil infrastructure systems is an important task that must be performed frequently in order to ensure their serviceability and sustainability. Additionally, laboratory experiments where individual system components are tested on the fine-scale level provide essential information during the structural design process. This type of inspection, i.e., measurements of deflections and/or cracks, has traditionally been performed with instrumentation that requires access to, or contact with, the structural element being tested; performs deformation measurements in only one dimension or direction; and/or provides no permanent visual record. To avoid the downsides of such instrumentation, this dissertation proposes a remote sensing approach based on a photogrammetric system capable of three-dimensional reconstruction. The proposed system is low-cost, consists of off-the-shelf components, and is capable of reconstructing objects or surfaces with homogeneous texture. The scientific contributions of this research work address the drawbacks in currently existing literature. Methods for in-situ multi-camera system calibration and system stability analysis are proposed in addition to methods for deflection/displacement monitoring, and crack detection and characterization in three dimensions. The mathematical model for the system calibration is based on a single or multiple reference camera(s) and built-in relative orientation constraints where the interior orientation and the mounting parameters for all cameras are explicitly estimated. The methods for system stability analysis can be used to comprehensively check for the cumulative impact of any changes in the system parameters. They also provide a quantitative measure of this impact on the reconstruction process in terms of image space units. Deflection/displacement monitoring of dynamic surfaces in three dimensions is achieved with the system by performing an innovative sinusoidal fitting adjustment. The input data for the adjustment comes from either model-based image fitting or full surface fitting procedures. The crack characterization, i.e., estimation of the average crack width, approximate length and overall orientation, is achieved directly in three dimensions by detecting cracks in a region of interest in a truly-rectified photo via image processing techniques. This hybrid approach combines the use of both geometric and radiometric data, and it performs best in a multi-epoch setting.
- ItemOpen AccessAn Investigation of Coordinates as Mathematical Evidence for Cadastral Surveying in Alberta(2021-04-27) Sakatch, Matthew Michael Philip; Rangelova, Elena; Detchev, Ivan; Lichti, Derek; O'Keefe, Kyle; Jacobson, DanThis research delves into the topic of coordinates as legal survey evidence for boundary positions. It is spurred by the recently adopted Hybrid Cadastre project in Alberta, Canada and the evidentiary changes concurrent with this initiative. A review of literature pertaining to how survey evidence in assessed historically under the Hierarchy of Evidence, as well as the implications of modern evidentiary initiatives with coordinates is provided. Hypotheses are formed from this literature review and enlighten the qualitative study design. Key informant interviews apprise of the profession’s perspectives on this form of evidence are assessed using qualitative methods. Informants included practicing land surveyors, academics, members of the public, and government officials. A descriptive narrative approach was applied to the informant’s feedback to generate emergent themes. Informant feedback was assessed against the themes by incorporating an ordinal scale to provide a parameterized data set. Inferences made from this dataset prime the synthesis and theory development. In synthesis, an emergent theory on coordinates as evidence is provided as well as a continuum for assessing coordinate based evidentiary initiatives. When properly framed within the legislative framework and in specific de facto applications coordinates can govern legal survey boundaries and be considered a sui generis form of boundary evidence. An emergent continuum is proposed to provide a metric for assessing future applications of coordinates as evidence in alternate jurisdictions. This continuum is founded in the principles of cadastral management, and ensuring the public's continued faith in the land framework. Conclusions are provided relating to the adoption of coordinates as evidence currently within the land framework and case law. Ultimately future adoption of coordinates as evidence is a topic that requires legislative intervention to provide for widespread adoption and acceptance.
- ItemOpen AccessMeasuring antler lengths using low-cost ToF cameras(2024-05-13) Cheng, Shu; Lichti, Derek; Matyas, John Robert; O'Keefe, Kyle; Bayat, Sayeh; Olsen, Michael J.Antlers have been widely used in pharmaceuticals, understanding regenerative mechanism, monitoring environmental pollutants as bio-indicators, and studying mechanical properties of bony tissues. Antler measurements play a significant role in these domains, indicating the antler growth stages, which are intricately linked to the medical properties, regenerative processes, and variations in pollutant levels within the antler. Traditionally, antler measurements are performed with contact methods like the measuring tape. The complex antler geometry entails multiple measurements and selection of reference points at various locations, making the process prone to human errors. The measuring process also requires manual capture or the use of drugs to keep the animal stationary, raising ethical and security concerns. To address these challenges and accurately monitor antler growth without causing any harm to the animals, an optical imaging method is proposed using a multi-camera system to obtain 3D antler data. The designed imaging system incorporates multiple Time-of-flight (ToF) cameras, an RGB camera, and an external trigger. The RGB camera detects animal motion, together with the external trigger, facilitates sequential data capture by the ToF cameras when animals are not moving substantially, thereby avoiding motion blur and camera interference. This mechanism ensures the collection of complete and usable antler data. In order to generate high quality antler data suitable for extracting measurements, a highly automated data processing workflow has been designed including antler quality control, segmentation, two-step registration and antler denoising. Animal motion and the low reflectivity of antlers are major factors degrading ToF camera data quality. To mitigate motion blur, animals are scanned during stationary periods and frames collected in each static period are merged as a weighted average for improved quality. The antler point cloud is automatically extracted by searching k-nearest neighbors from the environment data. The two-step registration involves registering multiple ToF cameras and aligning antler data from various static periods, which densify the antler data for manipulation. Ultimately, a polar coordinate-based denoising process filters out blunders and noise from the antler data for subsequent modelling process. An adaptive modelling approach has been developed to mathematically represent the antler data and facilitate measurement extraction. This method breaks down the 3D point cloud into slices and reconstructs the contour of each slice. The slice-based method strategically positions feature points where curvature changes occur, allowing for efficient storage and accurate reconstruction. Remarkably, this approach extends beyond antlers and can be applied to diverse shapes without prior knowledge. In summary, this research presents a comprehensive solution for monitoring antler growth, emphasizing precision, automation, and adaptability in the modeling processes and measurement extraction. This innovative approach not only advances antler related research but also lays the foundation for similar studies involving complex biological structures.
- ItemOpen AccessMulti-Sensor Integration for Indoor 3D Reconstruction(2014-05-02) Chow, Jacky; Lichti, Derek; Teskey, WilliamOutdoor maps and navigation information delivered by modern services and technologies like Google Maps and Garmin navigators have revolutionized the lifestyle of many people. Motivated by the desire for similar navigation systems for indoor usage from consumers, advertisers, emergency rescuers/responders, etc., many indoor environments such as shopping malls, museums, casinos, airports, transit stations, offices, and schools need to be mapped. Typically, the environment is first reconstructed by capturing many point clouds from various stations and defining their spatial relationships. Currently, there is a lack of an accurate, rigorous, and speedy method for relating point clouds in indoor, urban, satellite-denied environments. This thesis presents a novel and automatic way for fusing calibrated point clouds obtained using a terrestrial laser scanner and the Microsoft Kinect by integrating them with a low-cost inertial measurement unit. The developed system, titled the Scannect, is the first joint-static-kinematic indoor 3D mapper. Manmade instruments are susceptible to systematic distortions. These uncompensated errors can cause inconsistencies between the map and reality; for example a scale factor error can lead firefighters to the wrong rooms during rescue missions. For terrestrial laser scanners, marker-based user self-calibration has shown effectiveness, but has yet to gain popularity because it can be cumbersome to affix hundreds of targets inside a large room. Previous attempts to expedite this process involved removing the dependency on artificial signalized targets. However, the commonalities and differences of markerless approaches with respect to the marker-based method were not established. This research demonstrated with simulations and real data that using planar features can yield similar calibration results as using markers and much of the knowledge about marker-based calibration is transferable to the plane-based calibration method. For the Microsoft Kinect, there is a limited amount of research dedicated to calibrating the system. Most methods cannot handle the different onboard optical sensors simultaneously. Therefore, a novel and accurate total system calibration algorithm based on the bundle adjustment that can account for all inter-sensor correlations was developed. It is the first and only algorithm that functionally models the misalignments between the infrared camera and projector in addition to providing full variance-covariance information for all calibration parameters. Scan-matching and Kalman filtering are often used together by robots to fuse data from different sensors and perform Simultaneous Localisation and Mapping. However, most research that utilized the Kinect adopted the loosely-coupled paradigm and ignored the time synchronization error between the depth and colour information. A new measurement model that facilitates a tightly-coupled Kalman filter with an arbitrary number of Kinects was proposed. The depth and colour information were treated independently while being aided by inertial measurements, which yielded advantages over existing approaches. For the depth data, a new tightly-coupled iterative closest point algorithm that minimizes the reprojection errors of a triangulation-based 3D camera within an implicit iterative extended Kalman filter framework was developed. When texture variation becomes available, the RGB images automatically update the state vector by using a novel tightly-coupled 5-point visual odometry algorithm without state augmentation.