Extracting urban water bodies from high-resolution radar images: Measuring the urban surface morphology to control for radar’s double-bounce effect
Satellite remote sensing is an effective method for extracting water bodies on a large scale. Radar imagery, such as synthetic aperture radar (SAR) imagery, can penetrate clouds and provide opportunities for water body identification when in situ observations are difficult to obtain because of sever...
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| Format: | Article |
| Language: | English |
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Elsevier
2020-03-01
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| Series: | International Journal of Applied Earth Observations and Geoinformation |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0303243419306968 |
| _version_ | 1818245379809869824 |
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| author | Hao-Yu Liao Tzai-Hung Wen |
| author_facet | Hao-Yu Liao Tzai-Hung Wen |
| author_sort | Hao-Yu Liao |
| collection | DOAJ |
| description | Satellite remote sensing is an effective method for extracting water bodies on a large scale. Radar imagery, such as synthetic aperture radar (SAR) imagery, can penetrate clouds and provide opportunities for water body identification when in situ observations are difficult to obtain because of severe weather conditions. However, when using SAR images in urban areas to extract water bodies, the radar’s double-bounce effect results in complicated backscatter patterns of water near urban features such as buildings due to the side-looking properties of SAR sensors and the vertical urban structures. Therefore, the objective of this study is to propose a reliable urban water extraction framework for SAR images that integrates urban surface morphological features for controlling radar’s multiple bounces. Statistical (logistic regression) and machine-learning (random forest) models were used to explore how radar’s double-bounce effect influences the prediction performance of urban water extraction. Our findings indicate that when extracting urban water bodies, urban water’s backscatter values could be significantly interfered by the neighboring building density above a threshold height that contributes to radar’s multiple bounces. Without model calibration, our framework incorporating urban surface morphology demonstrates high prediction ability with an Area Under the Curve (AUC) of 0.914 and with 97.0% of urban water cells correctly identified by testing in another city sharing similar urban forms. In summary, our study provides a better understanding of the role of the urban surface morphology in the double-bounce effect in SAR images, specifically for differentiating urban water and land, thereby improving the accuracy of urban water extraction and enhancing the feasibility of further applications of SAR imagery under complex urban landscapes. |
| first_indexed | 2024-12-12T14:31:59Z |
| format | Article |
| id | doaj.art-9b3d684e2d6842dd9ea1af0537c88be9 |
| institution | Directory Open Access Journal |
| issn | 1569-8432 |
| language | English |
| last_indexed | 2024-12-12T14:31:59Z |
| publishDate | 2020-03-01 |
| publisher | Elsevier |
| record_format | Article |
| series | International Journal of Applied Earth Observations and Geoinformation |
| spelling | doaj.art-9b3d684e2d6842dd9ea1af0537c88be92022-12-22T00:21:28ZengElsevierInternational Journal of Applied Earth Observations and Geoinformation1569-84322020-03-0185102003Extracting urban water bodies from high-resolution radar images: Measuring the urban surface morphology to control for radar’s double-bounce effectHao-Yu Liao0Tzai-Hung Wen1Department of Geography, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, 10617, Taipei, TaiwanCorresponding author.; Department of Geography, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, 10617, Taipei, TaiwanSatellite remote sensing is an effective method for extracting water bodies on a large scale. Radar imagery, such as synthetic aperture radar (SAR) imagery, can penetrate clouds and provide opportunities for water body identification when in situ observations are difficult to obtain because of severe weather conditions. However, when using SAR images in urban areas to extract water bodies, the radar’s double-bounce effect results in complicated backscatter patterns of water near urban features such as buildings due to the side-looking properties of SAR sensors and the vertical urban structures. Therefore, the objective of this study is to propose a reliable urban water extraction framework for SAR images that integrates urban surface morphological features for controlling radar’s multiple bounces. Statistical (logistic regression) and machine-learning (random forest) models were used to explore how radar’s double-bounce effect influences the prediction performance of urban water extraction. Our findings indicate that when extracting urban water bodies, urban water’s backscatter values could be significantly interfered by the neighboring building density above a threshold height that contributes to radar’s multiple bounces. Without model calibration, our framework incorporating urban surface morphology demonstrates high prediction ability with an Area Under the Curve (AUC) of 0.914 and with 97.0% of urban water cells correctly identified by testing in another city sharing similar urban forms. In summary, our study provides a better understanding of the role of the urban surface morphology in the double-bounce effect in SAR images, specifically for differentiating urban water and land, thereby improving the accuracy of urban water extraction and enhancing the feasibility of further applications of SAR imagery under complex urban landscapes.http://www.sciencedirect.com/science/article/pii/S0303243419306968Synthetic aperture radar (SAR) imagesUrban morphologyWater body extractionRadar’s double-bounce effectSentinel-1 satellites |
| spellingShingle | Hao-Yu Liao Tzai-Hung Wen Extracting urban water bodies from high-resolution radar images: Measuring the urban surface morphology to control for radar’s double-bounce effect International Journal of Applied Earth Observations and Geoinformation Synthetic aperture radar (SAR) images Urban morphology Water body extraction Radar’s double-bounce effect Sentinel-1 satellites |
| title | Extracting urban water bodies from high-resolution radar images: Measuring the urban surface morphology to control for radar’s double-bounce effect |
| title_full | Extracting urban water bodies from high-resolution radar images: Measuring the urban surface morphology to control for radar’s double-bounce effect |
| title_fullStr | Extracting urban water bodies from high-resolution radar images: Measuring the urban surface morphology to control for radar’s double-bounce effect |
| title_full_unstemmed | Extracting urban water bodies from high-resolution radar images: Measuring the urban surface morphology to control for radar’s double-bounce effect |
| title_short | Extracting urban water bodies from high-resolution radar images: Measuring the urban surface morphology to control for radar’s double-bounce effect |
| title_sort | extracting urban water bodies from high resolution radar images measuring the urban surface morphology to control for radar s double bounce effect |
| topic | Synthetic aperture radar (SAR) images Urban morphology Water body extraction Radar’s double-bounce effect Sentinel-1 satellites |
| url | http://www.sciencedirect.com/science/article/pii/S0303243419306968 |
| work_keys_str_mv | AT haoyuliao extractingurbanwaterbodiesfromhighresolutionradarimagesmeasuringtheurbansurfacemorphologytocontrolforradarsdoublebounceeffect AT tzaihungwen extractingurbanwaterbodiesfromhighresolutionradarimagesmeasuringtheurbansurfacemorphologytocontrolforradarsdoublebounceeffect |