Comparison of forest canopy gap fraction measurements from drone-based video frames, below-canopy hemispherical photography, and airborne laser scanning
The amount of gaps in forest canopy is related to the radiation interception for photosynthesis and visibility through the canopy. The dependence of forest canopy gap fraction determination on view zenith angle was calculated from polar-transformed sparse ([Formula: see text]) airborne laser scannin...
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| Format: | Article |
| Language: | English |
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Taylor & Francis Group
2025-12-01
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| Series: | European Journal of Remote Sensing |
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| Online Access: | https://www.tandfonline.com/doi/10.1080/22797254.2025.2456629 |
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| author | Mait Lang Mikk Antsov Andres Mumma Indrek Suitso Andres Kuusk Kaarel Piip |
| author_facet | Mait Lang Mikk Antsov Andres Mumma Indrek Suitso Andres Kuusk Kaarel Piip |
| author_sort | Mait Lang |
| collection | DOAJ |
| description | The amount of gaps in forest canopy is related to the radiation interception for photosynthesis and visibility through the canopy. The dependence of forest canopy gap fraction determination on view zenith angle was calculated from polar-transformed sparse ([Formula: see text]) airborne laser scanning (ALS) point clouds for a Scots pine (Pinus sylvestris L.) stand growing on Kiriku Bog, Estonia. Visibility of ground targets was estimated from video image frames taken during drone (UAV) overpass at low altitude (40 m). Below-canopy digital hemispherical images (DHP) were taken in zenith direction as reference measurements. Angular grids of 3[Formula: see text] and 5[Formula: see text] were used to match the three data sources so as to decrease uncertainties in measurement geometries. The linear relationship between DHP and UAV data had [Formula: see text] = 0.67, with most of the deviations occurring at gap boundaries. Relationships over individual targets between DHP and polar-transformed ALS data had [Formula: see text]. However, the simulation overestimated gap fraction at smaller zenith angles because of uncertainties in constructing lidar pulse footprints from point data. We conclude that regional coverage by means of sparse ALS point clouds shows potential for the assessment of forest canopy gaps at off-nadir angles. |
| format | Article |
| id | doaj-art-8b7e6775bdcc4c47aae0e941db5ea9cf |
| institution | Kabale University |
| issn | 2279-7254 |
| language | English |
| publishDate | 2025-12-01 |
| publisher | Taylor & Francis Group |
| record_format | Article |
| series | European Journal of Remote Sensing |
| spelling | doaj-art-8b7e6775bdcc4c47aae0e941db5ea9cf2025-01-29T07:08:05ZengTaylor & Francis GroupEuropean Journal of Remote Sensing2279-72542025-12-0158110.1080/22797254.2025.2456629Comparison of forest canopy gap fraction measurements from drone-based video frames, below-canopy hemispherical photography, and airborne laser scanningMait Lang0Mikk Antsov1Andres Mumma2Indrek Suitso3Andres Kuusk4Kaarel Piip5Tartu Observatory, University of Tartu, Tõravere, EstoniaEstonian Military Academy, Tartu, EstoniaEstonian Academy of Security Sciences, Tallinn, EstoniaEstonian Military Academy, Tartu, EstoniaTartu Observatory, University of Tartu, Tõravere, EstoniaEstonian Military Academy, Tartu, EstoniaThe amount of gaps in forest canopy is related to the radiation interception for photosynthesis and visibility through the canopy. The dependence of forest canopy gap fraction determination on view zenith angle was calculated from polar-transformed sparse ([Formula: see text]) airborne laser scanning (ALS) point clouds for a Scots pine (Pinus sylvestris L.) stand growing on Kiriku Bog, Estonia. Visibility of ground targets was estimated from video image frames taken during drone (UAV) overpass at low altitude (40 m). Below-canopy digital hemispherical images (DHP) were taken in zenith direction as reference measurements. Angular grids of 3[Formula: see text] and 5[Formula: see text] were used to match the three data sources so as to decrease uncertainties in measurement geometries. The linear relationship between DHP and UAV data had [Formula: see text] = 0.67, with most of the deviations occurring at gap boundaries. Relationships over individual targets between DHP and polar-transformed ALS data had [Formula: see text]. However, the simulation overestimated gap fraction at smaller zenith angles because of uncertainties in constructing lidar pulse footprints from point data. We conclude that regional coverage by means of sparse ALS point clouds shows potential for the assessment of forest canopy gaps at off-nadir angles.https://www.tandfonline.com/doi/10.1080/22797254.2025.2456629View zenith anglevisibility of groundforestsparse point cloudpolar transformationdrone |
| spellingShingle | Mait Lang Mikk Antsov Andres Mumma Indrek Suitso Andres Kuusk Kaarel Piip Comparison of forest canopy gap fraction measurements from drone-based video frames, below-canopy hemispherical photography, and airborne laser scanning European Journal of Remote Sensing View zenith angle visibility of ground forest sparse point cloud polar transformation drone |
| title | Comparison of forest canopy gap fraction measurements from drone-based video frames, below-canopy hemispherical photography, and airborne laser scanning |
| title_full | Comparison of forest canopy gap fraction measurements from drone-based video frames, below-canopy hemispherical photography, and airborne laser scanning |
| title_fullStr | Comparison of forest canopy gap fraction measurements from drone-based video frames, below-canopy hemispherical photography, and airborne laser scanning |
| title_full_unstemmed | Comparison of forest canopy gap fraction measurements from drone-based video frames, below-canopy hemispherical photography, and airborne laser scanning |
| title_short | Comparison of forest canopy gap fraction measurements from drone-based video frames, below-canopy hemispherical photography, and airborne laser scanning |
| title_sort | comparison of forest canopy gap fraction measurements from drone based video frames below canopy hemispherical photography and airborne laser scanning |
| topic | View zenith angle visibility of ground forest sparse point cloud polar transformation drone |
| url | https://www.tandfonline.com/doi/10.1080/22797254.2025.2456629 |
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