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Remote Sensing for Land & Resources    2020, Vol. 32 Issue (1) : 35-42     DOI: 10.6046/gtzyyg.2020.01.06
Application of U-net model to water extraction with high resolution remote sensing data
Ning WANG1, Jiahua CHENG2(), Hanye ZHANG2, Hongjie CAO1,3, Jun LIU3
1. Beijing Unistrong Science and Technology Co., Ltd., Beijing 100015, China
2. East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai 200090, China
3. BeiDou Navigation and LBS (Beijing) Co., Ltd., Beijing 100191, China
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In this paper, the authors used a U-net model to conduct water extraction, and the result was compared with that of the random forest model. The accuracy of the U-net model was validated by using GF-1 images in Chaohu Lake Basin. The results show that both models are of high accuracy for large area of water body, but random forest model has more spots for small area of water body, and the result of U-net model is more consistent with the manual visual interpretation result. Moreover, the U-net model can effectively remove the shadows of mountains and buildings. The result indicates that U-net model performs better than random forest model with the overall accuracy of 98.69%, Kappa coefficient of 0.95, omission error of 1.90% and commission error of 1.18%. In contrast, the overall accuracy, Kappa coefficient, omission error and commission error of random forest model are about 98.05%, 0.92, 1.61% and 2.99%, respectively. In addition, the classification features for traditional machine learning model are always calculated by manual extraction. However, the inputs for U-net model are the 4 band spectrum data of GF-1 images. These data suggest that the U-net model avoids the process of manually extracting classification features and has a higher degree of automation. It should be noted that the U-net model uses more train samples with less time-consuming. It is believed that this model can significantly improve the surface water detection accuracy and can be used for the automatic renewal of a larger range of water bodies.

Keywords GF-1      U-net      random forest      water extraction     
:  TP79  
Corresponding Authors: Jiahua CHENG     E-mail:
Issue Date: 14 March 2020
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Cite this article:   
Ning WANG,Jiahua CHENG,Hanye ZHANG, et al. Application of U-net model to water extraction with high resolution remote sensing data[J]. Remote Sensing for Land & Resources, 2020, 32(1): 35-42.
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Fig.1  Location of the study area
Fig.2  Structure of the U-net model
评价指标 计算方法
总体精度 正确分类像元数占总像元数的比例
Kappa系数 Kappa=Nxii-(xi·x·i)N2-(xi·x·i)
漏分误差 水体错分为非水体的像元数占真实水体总像元数的比例
错分误差 非水体错分为水体的像元数占分类得到水体总像元数的比例
Tab.1  Evaluation indexes on remote sensing image classification results
Fig.3  Comparison of the water extraction results between U-net and random forest
Fig.4  Comparison of the extraction results for small water bodies
Fig.5  Comparison of shadow removal results by U-net and random forest
模型 总体精度/% Kappa 漏分误差/% 错分误差/%
U-net 98.69 0.95 1.90 1.18
随机森林 98.05 0.92 1.61 2.99
Tab.2  Comparison of water extraction accuracy
模型 训练样本数/(像元×像元) 耗时/s
U-net 14 200×8 000 1 136
随机森林 14 200×100 14 126
Tab.3  Efficiency of different models for water extraction
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