Evaluating the performance of multi-rotor UAV-Sfm imagery in assessing simple and complex forest structures: comparison to advanced remote sensing sensors

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dc.contributor.advisorSmit, Julian
dc.contributor.authorOnwudinjo, Kenechukwu Chukwudubem
dc.date.accessioned2022-03-08T10:19:17Z
dc.date.available2022-03-08T10:19:17Z
dc.date.issued2021
dc.date.updated2022-03-08T10:15:55Z
dc.description.abstractThe 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.
dc.identifier.apacitationOnwudinjo, K. C. (2021). <i>Evaluating the performance of multi-rotor UAV-Sfm imagery in assessing simple and complex forest structures: comparison to advanced remote sensing sensors</i>. (). ,Faculty of Engineering and the Built Environment ,School of Architecture, Planning and Geomatics. Retrieved from http://hdl.handle.net/11427/35996en_ZA
dc.identifier.chicagocitationOnwudinjo, Kenechukwu Chukwudubem. <i>"Evaluating the performance of multi-rotor UAV-Sfm imagery in assessing simple and complex forest structures: comparison to advanced remote sensing sensors."</i> ., ,Faculty of Engineering and the Built Environment ,School of Architecture, Planning and Geomatics, 2021. http://hdl.handle.net/11427/35996en_ZA
dc.identifier.citationOnwudinjo, K.C. 2021. Evaluating the performance of multi-rotor UAV-Sfm imagery in assessing simple and complex forest structures: comparison to advanced remote sensing sensors. . ,Faculty of Engineering and the Built Environment ,School of Architecture, Planning and Geomatics. http://hdl.handle.net/11427/35996en_ZA
dc.identifier.ris TY - Master Thesis AU - Onwudinjo, Kenechukwu Chukwudubem AB - 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. DA - 2021 DB - OpenUCT DP - University of Cape Town KW - Unmanned Aerial Vehicles KW - Structure‐from-Motion KW - Aerial Laser Scanning KW - Terrestrial Laser Scanning KW - Tree Height KW - Diameter at Breast Height KW - Biomass LK - https://open.uct.ac.za PY - 2021 T1 - Evaluating the performance of multi-rotor UAV-Sfm imagery in assessing simple and complex forest structures: comparison to advanced remote sensing sensors TI - Evaluating the performance of multi-rotor UAV-Sfm imagery in assessing simple and complex forest structures: comparison to advanced remote sensing sensors UR - http://hdl.handle.net/11427/35996 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/35996
dc.identifier.vancouvercitationOnwudinjo KC. Evaluating the performance of multi-rotor UAV-Sfm imagery in assessing simple and complex forest structures: comparison to advanced remote sensing sensors. []. ,Faculty of Engineering and the Built Environment ,School of Architecture, Planning and Geomatics, 2021 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/35996en_ZA
dc.language.rfc3066eng
dc.publisher.departmentSchool of Architecture, Planning and Geomatics
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.subjectUnmanned Aerial Vehicles
dc.subjectStructure‐from-Motion
dc.subjectAerial Laser Scanning
dc.subjectTerrestrial Laser Scanning
dc.subjectTree Height
dc.subjectDiameter at Breast Height
dc.subjectBiomass
dc.titleEvaluating the performance of multi-rotor UAV-Sfm imagery in assessing simple and complex forest structures: comparison to advanced remote sensing sensors
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationlevelMSc
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