1,656 research outputs found
Design and evaluation of multispectral LiDAR for the recovery of arboreal parameters
No full textMultispectral light detection and ranging (LiDAR) has the potential to recover structural and physiological data from arboreal samples and, by extension, from forest canopies when deployed on aerial or space platforms. In this paper, we describe the design and evaluation of a prototype multispectral LiDAR system and demonstrate the measurement of leaf and bark area and abundance profiles using a series of experiments on tree samples “viewed from above” by tilting living conifers such that the apex is directed on the viewing axis. As the complete recovery of all structural and physiological parameters is ill posed with a restricted set of four wavelengths, we used leaf and bark spectra measured in the laboratory to constrain parameter inversion by an extended reversible jump Markov chain Monte Carlo algorithm. However, we also show in a separate experiment how the multispectral LiDAR can recover directly a profile of Normalized Difference Vegetation Index (NDVI), which is verified against the laboratory spectral measurements. Our work shows the potential of multispectral LiDAR to recover both structural and physiological data and also highlights the fine spatial resolution that can be achieved with time-correlated single-photon countin
sj-pdf-1-jso-10.1177_23971983221138712 – Supplemental material for Development and validation of Hebrew version of the UCLA Scleroderma Clinical Trial Consortium Gastrointestinal Tract Instrument 2.0
No full textSupplemental material, sj-pdf-1-jso-10.1177_23971983221138712 for Development and validation of Hebrew version of the UCLA Scleroderma Clinical Trial Consortium Gastrointestinal Tract Instrument 2.0 by David Ozeri, Shani Peretz, Amit Oppenheim, Abdallah Watad, Merav Lidar and Yolanda Braun-Moscovici in Journal of Scleroderma and Related Disorders</p
LiDAR-guided dense matching for detecting changes and updating of buildings in Airborne LiDAR data
No full textChange detection is essential to keep 3D city models up-to-date. LiDAR data with high accuracy are used to create 3D city models. However, updating LiDAR data at state or nation level often takes around a decade. Very high resolution (VHR) stereo images, with often yearly updating rate and dense 3D information, provide an option for validating and updating LiDAR data. However, the 3D information in both data sources has quality problems. LiDAR point clouds are sparse and irregularly spaced, and have mixed returns near building edges, while 3D information extracted from stereo images are affected by shadow and low texture. This research proposes LiDAR-guided dense matching to address these problems explicitly for detecting accurate building changes. Data sparsity and irregular spacing is addressed by densifying LiDAR points in a form of a digital surface model (DSM). Instead of applying interpolation with associated edge problems due to mixed returns, three candidate DSMs are created by linking each DSM pixel to up to three planes as identified in segmented and triangulated LiDAR data. The candidate DSMs limit the disparity search space for dense matching, addressing low texture and shadow problems in images. Through edge-aware dense matching, the detailed building edge information in stereo pairs determine the optimal heights to address LiDAR edge problem. Changes are detected where corresponding pixels from dense matching have large color differences. Due to homogeneous surroundings and shadows, only partial changes are initially detected. A second hierarchical dense matching step is employed to complete changes and update 3D information by propagating initial partial changes iteratively. The proposed method is applied on data from two cities, Amersfoort and Assen, the Netherlands, with around 1200 existing buildings. In both areas, the method successfully verifies unchanged buildings while detecting minimum changes of 2×2×2m3. New and removed building detection in Amersfoort both have a F1 score of over 0.8, both in pixel and object evaluation, while F1 scores in Assen are over 0.9 for both categories. The experiments also show that the proposed method outperforms two well-known change detection methods in terms of verifying unchanged buildings and detecting small changes simultaneously.Accepted Author ManuscriptOptical and Laser Remote Sensin
Storing and analysing massive aerial LIDAR datasets in a DBMS
No full textOTB onderzoekOTB Research Institute for the Built Environmen
Design of a Deep Sea LiDAR System: Laser Pulse Reception and LiDAR Control Logic
No full textCurrent subsea LiDAR implementations are inherently depth limited, and make LiDAR applications in the deep-sea costly. To this end, the SLiDAR project aims to develop a pressure tolerant LiDAR system for use at any ocean depth. This thesis elaborates the high-level system design of the LiDAR system, as well as the design and implementation of the laser pulse reception stage and the onboard central control unit. Due to the short time frame of the project and the high work load, the LiDAR system as a whole and its subsystems are not tested in practise. Hence, this thesis aims to provide a basis for future development, testing and verification of both the LiDAR system, its laser reception stage, and its central control unit.SLiDARElectrical Engineering | Circuits and System
Graph Based LiDAR-Inertial Lo- calization with a Low Power Solid State LiDAR
No full textMapping an environment with a Light Detection and Ranging (LiDAR) sensor through the use of a LiDAR Simultaneous Localization And Mapping (SLAM) algorithm is a powerful technology that allows for the creation of detailed 3D models. Recently various LiDAR sensors have been developed based on Micro-Electro-Mechanical System (MEMS) technology. These LiDARs are very low cost and considerably smaller than conventional LiDARs. They also often incorporate other sensors such as Inertial Measurement Unit (IMU)s and cameras into the same device. Performing LiDAR SLAM with MEMS based LiDAR is challenging due to the short range, the smaller Field of View (FOV) and the sensitivity to ambient light of MEMS based LiDAR. In this thesis the objective is to reduce the effect of these factors when doing LiDAR SLAM by incorporating IMU measurements into the position estimation of the sensor.A graph based positioning approach is proposed to achieve tight coupling of the IMU sensor and LiDAR position estimates. The method is made more robust by incorporating an outlier detection mechanism that reduces the influence of wrong LiDAR position estimates caused by insufficient points in the LiDAR FOV or by ambient light disturbance.The method was built in ROS and implemented on the Intel ® L515 sensor. The performance is evaluated in indoor situations with varying presence of ambient sunlight and where room size approaches the maximum limit of the sensor range. The algorithm achieves lower drift than the current state of the art for the Intel ® L515. The algorithm especially achieves altitude drift reduction and increases robustness to outliers in the LiDAR positioning.Mechanical Engineering | Systems and Contro
Design of a deep sea LiDAR system: Laser Pulse transmission
No full textCurrent subsea LiDAR implementations are inherently depth limited, and make LiDAR applications in the deep-sea costly. To this end, the SLiDAR project aims to develop a pressure tolerant LiDAR system for use at any ocean depth. This thesis elaborates the design and implementation of the laser pulse transmission of the LiDAR and the circuit which will supply the bias voltage for the Avalanche photodiode (APD) from the receiving stage. Although testing of the transmission stage showed the laser can be pulsed, there can be more optimizations done in the future as better laser system can be designed to achieve higher optical output power and an even smaller pulse width. Furthermore,future optimizations should be considered for the APD bias circuit. Unfortunately, the LiDAR system as a whole was not tested in practise, due to time limitations. Hence, this thesis aims to provide a basis for future development, testing and verification of both the LiDAR system and its laser pulse transmission stage.SLiDARElectrical Engineerin
3D Habitat Mapping Using High-Resolution Optical Satellite and Lidar Data
No full textRemote sensing datasets are great resources to map habitat types. In this study, 3D habitat maps were generated using high-resolution multispectral imagery and a LiDAR-derived digital surface model (DSM). Two study areas in the United Kingdom (UK) were selected to investigate the potential of the developed models in habitat classification. The overall classification accuracies for the two study areas were high (91% and 82%), indicating the satisfactory performance of the developed approach for habitat mapping in the study areas. Overall, it was observed that a synergy of high-resolution multi-spectral imagery and LiDAR data could provide reliable 3D information on habitat types.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Geo-engineerin
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