First Demonstration of Space-Borne Polarization Coherence Tomography for Characterizing Hyrcanian Forest Structural Diversity
Structural diversity is recognized as a complementary aspect of biological diversity and plays a fundamental role in forest management, conservation, and restoration. Hence, the assessment of structural diversity has become a major effort in the primary international processes, dealing with biodiver...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-01-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/15/3/555 |
| _version_ | 1797623403769757696 |
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| author | Maryam Poorazimy Shaban Shataee Hossein Aghababaei Erkki Tomppo Jaan Praks |
| author_facet | Maryam Poorazimy Shaban Shataee Hossein Aghababaei Erkki Tomppo Jaan Praks |
| author_sort | Maryam Poorazimy |
| collection | DOAJ |
| description | Structural diversity is recognized as a complementary aspect of biological diversity and plays a fundamental role in forest management, conservation, and restoration. Hence, the assessment of structural diversity has become a major effort in the primary international processes, dealing with biodiversity and sustainable forest management. Because of prohibitive costs associated with the ground measurements of forest structure, despite their high accuracy, space-borne polarization coherence tomography (PCT) can introduce an alternative approach given its ability to provide a vertical reflectivity profile and spatiotemporal resolutions related to detecting forest structural changes. In this study, for the first time ever, the potential of space-borne PCT was evaluated in a broad-leaved Hyrcanian forest of Iran over 308 circular sample plots with an area of 0.1 ha. Two aspects of horizontal structure diversity, including standard deviation of diameter at breast height (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>d</mi><mi>b</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula>) and the number of trees (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>N</mi></semantics></math></inline-formula>), were predicted as important characteristics in wood production and biomass estimation. In addition, the performance of prediction algorithms, including multiple linear regression (MLR), <i>k</i>-nearest neighbors (<i>k</i>-NN), random forest (RF), and support vector regression (SVR) were compared. We addressed the issue of temporal decorrelation in space-borne PCT utilizing the single-pass TanDEM-X interferometer. The data were acquired in standard DEM mode with single polarization of HH. Consequently, airborne laser scanning (ALS) was used to estimate initial values of height <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>h</mi><mi>v</mi></msub></mrow></semantics></math></inline-formula> and ground phase <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>φ</mi><mn>0</mn></msub></mrow></semantics></math></inline-formula>. The Fourier–Legendre series was used to approximate the relative reflectivity profile of each pixel. To link the relative reflectivity profile averaged within each plot with corresponding ground measurements of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>d</mi><mi>b</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>N</mi></semantics></math></inline-formula>, thirteen geometrical and physical parameters were defined (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mn>1</mn><mo>−</mo><mi>P</mi><mn>13</mn></mrow></semantics></math></inline-formula>). Leave-one-out cross validation (LOOCV) showed a better performance of <i>k</i>-NN than the other algorithms in predicting <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>d</mi><mi>b</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>N</mi></semantics></math></inline-formula>. It resulted in a relative root mean square error (rRMSE) of 32.80%, mean absolute error (MAE) of 4.69 cm, and R<sup>2</sup>* of 0.25 for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>d</mi><mi>b</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula>, whereas only 22% of the variation in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>N</mi></semantics></math></inline-formula> was explained using the PCT algorithm with an rRMSE of 41.56%. This study revealed promising results utilizing TanDEM-X data even though the accuracy is still limited. Hence, an entire assessment of the used framework in characterizing the reflectivity profile and the possible effect of the scale is necessary for future studies. |
| first_indexed | 2024-03-11T09:28:26Z |
| format | Article |
| id | doaj.art-8749a3a243cc4eb9ac92b5e3bab17fd1 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-11T09:28:26Z |
| publishDate | 2023-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-8749a3a243cc4eb9ac92b5e3bab17fd12023-11-16T17:50:54ZengMDPI AGRemote Sensing2072-42922023-01-0115355510.3390/rs15030555First Demonstration of Space-Borne Polarization Coherence Tomography for Characterizing Hyrcanian Forest Structural DiversityMaryam Poorazimy0Shaban Shataee1Hossein Aghababaei2Erkki Tomppo3Jaan Praks4Department of Electronics and Nanoengineering, Aalto University, 02150 Espoo, FinlandDepartment of Forestry, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan 49189-43464, IranDepartment of Earth Observation Science, University of Twente, 7514AE Enschede, The NetherlandsDepartment of Forest Sciences, University of Helsinki, 00014 Helsinki, FinlandDepartment of Electronics and Nanoengineering, Aalto University, 02150 Espoo, FinlandStructural diversity is recognized as a complementary aspect of biological diversity and plays a fundamental role in forest management, conservation, and restoration. Hence, the assessment of structural diversity has become a major effort in the primary international processes, dealing with biodiversity and sustainable forest management. Because of prohibitive costs associated with the ground measurements of forest structure, despite their high accuracy, space-borne polarization coherence tomography (PCT) can introduce an alternative approach given its ability to provide a vertical reflectivity profile and spatiotemporal resolutions related to detecting forest structural changes. In this study, for the first time ever, the potential of space-borne PCT was evaluated in a broad-leaved Hyrcanian forest of Iran over 308 circular sample plots with an area of 0.1 ha. Two aspects of horizontal structure diversity, including standard deviation of diameter at breast height (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>d</mi><mi>b</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula>) and the number of trees (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>N</mi></semantics></math></inline-formula>), were predicted as important characteristics in wood production and biomass estimation. In addition, the performance of prediction algorithms, including multiple linear regression (MLR), <i>k</i>-nearest neighbors (<i>k</i>-NN), random forest (RF), and support vector regression (SVR) were compared. We addressed the issue of temporal decorrelation in space-borne PCT utilizing the single-pass TanDEM-X interferometer. The data were acquired in standard DEM mode with single polarization of HH. Consequently, airborne laser scanning (ALS) was used to estimate initial values of height <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>h</mi><mi>v</mi></msub></mrow></semantics></math></inline-formula> and ground phase <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>φ</mi><mn>0</mn></msub></mrow></semantics></math></inline-formula>. The Fourier–Legendre series was used to approximate the relative reflectivity profile of each pixel. To link the relative reflectivity profile averaged within each plot with corresponding ground measurements of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>d</mi><mi>b</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>N</mi></semantics></math></inline-formula>, thirteen geometrical and physical parameters were defined (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mn>1</mn><mo>−</mo><mi>P</mi><mn>13</mn></mrow></semantics></math></inline-formula>). Leave-one-out cross validation (LOOCV) showed a better performance of <i>k</i>-NN than the other algorithms in predicting <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>d</mi><mi>b</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>N</mi></semantics></math></inline-formula>. It resulted in a relative root mean square error (rRMSE) of 32.80%, mean absolute error (MAE) of 4.69 cm, and R<sup>2</sup>* of 0.25 for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>d</mi><mi>b</mi><mi>h</mi></mrow></msub></mrow></semantics></math></inline-formula>, whereas only 22% of the variation in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>N</mi></semantics></math></inline-formula> was explained using the PCT algorithm with an rRMSE of 41.56%. This study revealed promising results utilizing TanDEM-X data even though the accuracy is still limited. Hence, an entire assessment of the used framework in characterizing the reflectivity profile and the possible effect of the scale is necessary for future studies.https://www.mdpi.com/2072-4292/15/3/555SARbroad-leaved forestsPCTstandard deviation of dbhnumber of treesTanDEM-X |
| spellingShingle | Maryam Poorazimy Shaban Shataee Hossein Aghababaei Erkki Tomppo Jaan Praks First Demonstration of Space-Borne Polarization Coherence Tomography for Characterizing Hyrcanian Forest Structural Diversity Remote Sensing SAR broad-leaved forests PCT standard deviation of dbh number of trees TanDEM-X |
| title | First Demonstration of Space-Borne Polarization Coherence Tomography for Characterizing Hyrcanian Forest Structural Diversity |
| title_full | First Demonstration of Space-Borne Polarization Coherence Tomography for Characterizing Hyrcanian Forest Structural Diversity |
| title_fullStr | First Demonstration of Space-Borne Polarization Coherence Tomography for Characterizing Hyrcanian Forest Structural Diversity |
| title_full_unstemmed | First Demonstration of Space-Borne Polarization Coherence Tomography for Characterizing Hyrcanian Forest Structural Diversity |
| title_short | First Demonstration of Space-Borne Polarization Coherence Tomography for Characterizing Hyrcanian Forest Structural Diversity |
| title_sort | first demonstration of space borne polarization coherence tomography for characterizing hyrcanian forest structural diversity |
| topic | SAR broad-leaved forests PCT standard deviation of dbh number of trees TanDEM-X |
| url | https://www.mdpi.com/2072-4292/15/3/555 |
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