A New Threshold-Based Method for Extracting Canopy Temperature from Thermal Infrared Images of Cork Oak Plantations
Canopy temperature (T<sub>c</sub>) is used to characterize plant water physiology, and thermal infrared (TIR) remote sensing is a convenient technology for measuring T<sub>c</sub> in forest ecosystems. However, the images produced through this method contain background pixels...
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MDPI AG
2021-12-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/13/24/5028 |
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| author | Linqi Liu Yingchao Xie Xiang Gao Xiangfen Cheng Hui Huang Jinsong Zhang |
| author_facet | Linqi Liu Yingchao Xie Xiang Gao Xiangfen Cheng Hui Huang Jinsong Zhang |
| author_sort | Linqi Liu |
| collection | DOAJ |
| description | Canopy temperature (T<sub>c</sub>) is used to characterize plant water physiology, and thermal infrared (TIR) remote sensing is a convenient technology for measuring T<sub>c</sub> in forest ecosystems. However, the images produced through this method contain background pixels of forest gaps, thereby reducing the accuracy of T<sub>c</sub> observations. Extracting T<sub>c</sub> data from TIR images is of great significance for understanding changes in ecosystem water status. In this study, a temperature threshold method was developed to rapidly, accurately, and automatically extract forest canopy pixels for T<sub>c</sub> data obtention. Specifically, this method takes the temperature corresponding to the point with a slope of 0.5 in the curve composed of the normalized average temperature and the normalized cumulative number of pixels as the segmentation threshold to separate the forest gap pixels from the forest canopy pixels in the TIR images and extract the separated forest canopy pixels based on the pixel coordinates for T<sub>c</sub> data obtention. Taking the T<sub>c</sub> values, measured using a thermocouple, as the standard, T<sub>c</sub> extraction using the new temperature threshold method and traditional methods (the Otsu algorithm and direct extraction) was compared in cork oak plantations. The results showed that the temperature threshold method offered the highest extraction accuracy, followed by the direct extraction method and the Otsu algorithm. The temperature threshold method was determined to be the most suitable for extracting T<sub>c</sub> data from the TIR images of cork oak plantations. |
| first_indexed | 2024-03-10T03:12:00Z |
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| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T03:12:00Z |
| publishDate | 2021-12-01 |
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| series | Remote Sensing |
| spelling | doaj.art-d6429ff587cc412399f52eaf5d282b182023-11-23T10:23:53ZengMDPI AGRemote Sensing2072-42922021-12-011324502810.3390/rs13245028A New Threshold-Based Method for Extracting Canopy Temperature from Thermal Infrared Images of Cork Oak PlantationsLinqi Liu0Yingchao Xie1Xiang Gao2Xiangfen Cheng3Hui Huang4Jinsong Zhang5Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, ChinaCollege of Forestry, Henan Agricultural University, Zhengzhou 450002, ChinaKey Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, ChinaKey Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, ChinaKey Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, ChinaKey Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, ChinaCanopy temperature (T<sub>c</sub>) is used to characterize plant water physiology, and thermal infrared (TIR) remote sensing is a convenient technology for measuring T<sub>c</sub> in forest ecosystems. However, the images produced through this method contain background pixels of forest gaps, thereby reducing the accuracy of T<sub>c</sub> observations. Extracting T<sub>c</sub> data from TIR images is of great significance for understanding changes in ecosystem water status. In this study, a temperature threshold method was developed to rapidly, accurately, and automatically extract forest canopy pixels for T<sub>c</sub> data obtention. Specifically, this method takes the temperature corresponding to the point with a slope of 0.5 in the curve composed of the normalized average temperature and the normalized cumulative number of pixels as the segmentation threshold to separate the forest gap pixels from the forest canopy pixels in the TIR images and extract the separated forest canopy pixels based on the pixel coordinates for T<sub>c</sub> data obtention. Taking the T<sub>c</sub> values, measured using a thermocouple, as the standard, T<sub>c</sub> extraction using the new temperature threshold method and traditional methods (the Otsu algorithm and direct extraction) was compared in cork oak plantations. The results showed that the temperature threshold method offered the highest extraction accuracy, followed by the direct extraction method and the Otsu algorithm. The temperature threshold method was determined to be the most suitable for extracting T<sub>c</sub> data from the TIR images of cork oak plantations.https://www.mdpi.com/2072-4292/13/24/5028plantation canopy temperature extractionthermal infrared imagesthe temperature threshold methodthe Otsu algorithmthe direct extraction method |
| spellingShingle | Linqi Liu Yingchao Xie Xiang Gao Xiangfen Cheng Hui Huang Jinsong Zhang A New Threshold-Based Method for Extracting Canopy Temperature from Thermal Infrared Images of Cork Oak Plantations Remote Sensing plantation canopy temperature extraction thermal infrared images the temperature threshold method the Otsu algorithm the direct extraction method |
| title | A New Threshold-Based Method for Extracting Canopy Temperature from Thermal Infrared Images of Cork Oak Plantations |
| title_full | A New Threshold-Based Method for Extracting Canopy Temperature from Thermal Infrared Images of Cork Oak Plantations |
| title_fullStr | A New Threshold-Based Method for Extracting Canopy Temperature from Thermal Infrared Images of Cork Oak Plantations |
| title_full_unstemmed | A New Threshold-Based Method for Extracting Canopy Temperature from Thermal Infrared Images of Cork Oak Plantations |
| title_short | A New Threshold-Based Method for Extracting Canopy Temperature from Thermal Infrared Images of Cork Oak Plantations |
| title_sort | new threshold based method for extracting canopy temperature from thermal infrared images of cork oak plantations |
| topic | plantation canopy temperature extraction thermal infrared images the temperature threshold method the Otsu algorithm the direct extraction method |
| url | https://www.mdpi.com/2072-4292/13/24/5028 |
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