Growth Height Determination of Tree Walls for Precise Monitoring in Apple Fruit Production Using UAV Photogrammetry
In apple cultivation, spatial information about phenotypic characteristics of tree walls would be beneficial for precise orchard management. Unmanned aerial vehicles (UAVs) can collect 3D structural information of ground surface objects at high resolution in a cost-effective and versatile way by usi...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2020-05-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/12/10/1656 |
| _version_ | 1797567291821391872 |
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| author | Marius Hobart Michael Pflanz Cornelia Weltzien Michael Schirrmann |
| author_facet | Marius Hobart Michael Pflanz Cornelia Weltzien Michael Schirrmann |
| author_sort | Marius Hobart |
| collection | DOAJ |
| description | In apple cultivation, spatial information about phenotypic characteristics of tree walls would be beneficial for precise orchard management. Unmanned aerial vehicles (UAVs) can collect 3D structural information of ground surface objects at high resolution in a cost-effective and versatile way by using photogrammetry. The aim of this study is to delineate tree wall height information in an apple orchard applying a low-altitude flight pattern specifically designed for UAVs. This flight pattern implies small distances between the camera sensor and the tree walls when the camera is positioned in an oblique view toward the trees. In this way, it is assured that the depicted tree crown wall area will be largely covered with a larger ground sampling distance than that recorded from a nadir perspective, especially regarding the lower crown sections. Overlapping oblique view images were used to estimate 3D point cloud models by applying structure-from-motion (SfM) methods to calculate tree wall heights from them. The resulting height models were compared with ground-based light detection and ranging (LiDAR) data as reference. It was shown that the tree wall profiles from the UAV point clouds were strongly correlated with the LiDAR point clouds of two years (2018: R<sup>2</sup> = 0.83; 2019: R<sup>2</sup> = 0.88). However, underestimation of tree wall heights was detected with mean deviations of −0.11 m and −0.18 m for 2018 and 2019, respectively. This is attributed to the weaknesses of the UAV point clouds in resolving the very fine shoots of apple trees. Therefore, the shown approach is suitable for precise orchard management, but it underestimated vertical tree wall expanses, and widened tree gaps need to be accounted for. |
| first_indexed | 2024-03-10T19:40:39Z |
| format | Article |
| id | doaj.art-65f557e989ef4bc2bf37d9719988afa8 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T19:40:39Z |
| publishDate | 2020-05-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-65f557e989ef4bc2bf37d9719988afa82023-11-20T01:18:52ZengMDPI AGRemote Sensing2072-42922020-05-011210165610.3390/rs12101656Growth Height Determination of Tree Walls for Precise Monitoring in Apple Fruit Production Using UAV PhotogrammetryMarius Hobart0Michael Pflanz1Cornelia Weltzien2Michael Schirrmann3Leibniz Institute for Agricultural Engineering and Bioeconomy, 14469 Potsdam, GermanyLeibniz Institute for Agricultural Engineering and Bioeconomy, 14469 Potsdam, GermanyLeibniz Institute for Agricultural Engineering and Bioeconomy, 14469 Potsdam, GermanyLeibniz Institute for Agricultural Engineering and Bioeconomy, 14469 Potsdam, GermanyIn apple cultivation, spatial information about phenotypic characteristics of tree walls would be beneficial for precise orchard management. Unmanned aerial vehicles (UAVs) can collect 3D structural information of ground surface objects at high resolution in a cost-effective and versatile way by using photogrammetry. The aim of this study is to delineate tree wall height information in an apple orchard applying a low-altitude flight pattern specifically designed for UAVs. This flight pattern implies small distances between the camera sensor and the tree walls when the camera is positioned in an oblique view toward the trees. In this way, it is assured that the depicted tree crown wall area will be largely covered with a larger ground sampling distance than that recorded from a nadir perspective, especially regarding the lower crown sections. Overlapping oblique view images were used to estimate 3D point cloud models by applying structure-from-motion (SfM) methods to calculate tree wall heights from them. The resulting height models were compared with ground-based light detection and ranging (LiDAR) data as reference. It was shown that the tree wall profiles from the UAV point clouds were strongly correlated with the LiDAR point clouds of two years (2018: R<sup>2</sup> = 0.83; 2019: R<sup>2</sup> = 0.88). However, underestimation of tree wall heights was detected with mean deviations of −0.11 m and −0.18 m for 2018 and 2019, respectively. This is attributed to the weaknesses of the UAV point clouds in resolving the very fine shoots of apple trees. Therefore, the shown approach is suitable for precise orchard management, but it underestimated vertical tree wall expanses, and widened tree gaps need to be accounted for.https://www.mdpi.com/2072-4292/12/10/1656oblique viewstructure from motion (SfM)3D point cloudunmanned aerial vehicle (UAV)LiDARsite-specific |
| spellingShingle | Marius Hobart Michael Pflanz Cornelia Weltzien Michael Schirrmann Growth Height Determination of Tree Walls for Precise Monitoring in Apple Fruit Production Using UAV Photogrammetry Remote Sensing oblique view structure from motion (SfM) 3D point cloud unmanned aerial vehicle (UAV) LiDAR site-specific |
| title | Growth Height Determination of Tree Walls for Precise Monitoring in Apple Fruit Production Using UAV Photogrammetry |
| title_full | Growth Height Determination of Tree Walls for Precise Monitoring in Apple Fruit Production Using UAV Photogrammetry |
| title_fullStr | Growth Height Determination of Tree Walls for Precise Monitoring in Apple Fruit Production Using UAV Photogrammetry |
| title_full_unstemmed | Growth Height Determination of Tree Walls for Precise Monitoring in Apple Fruit Production Using UAV Photogrammetry |
| title_short | Growth Height Determination of Tree Walls for Precise Monitoring in Apple Fruit Production Using UAV Photogrammetry |
| title_sort | growth height determination of tree walls for precise monitoring in apple fruit production using uav photogrammetry |
| topic | oblique view structure from motion (SfM) 3D point cloud unmanned aerial vehicle (UAV) LiDAR site-specific |
| url | https://www.mdpi.com/2072-4292/12/10/1656 |
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