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Article

Multi-Spectral Water Index (MuWI): A Native 10-m Multi-Spectral Water Index for Accurate Water Mapping on Sentinel-2

1
School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
2
Department of Geography, The University of Hong Kong, Hong Kong 999077, China
3
School of Geographical Sciences, Guangzhou University, Guangzhou 510006, China
*
Author to whom correspondence should be addressed.
Remote Sens. 2018, 10(10), 1643; https://doi.org/10.3390/rs10101643
Received: 21 August 2018 / Revised: 25 September 2018 / Accepted: 12 October 2018 / Published: 16 October 2018
(This article belongs to the Section Remote Sensing in Geology, Geomorphology and Hydrology)
Accurate water mapping depends largely on the water index. However, most previously widely-adopted water index methods are developed from 30-m resolution Landsat imagery, with low-albedo commission error (e.g., shadow misclassified as water) and threshold instability being identified as the primary issues. Besides, since the shortwave-infrared (SWIR) spectral band (band 11) on Sentinel-2 is 20 m spatial resolution, current SWIR-included water index methods usually produce water maps at 20 m resolution instead of the highest 10 m resolution of Sentinel-2 bands, which limits the ability of Sentinel-2 to detect surface water at finer scales. This study aims to develop a water index from Sentinel-2 that improves native resolution and accuracy of water mapping at the same time. Support Vector Machine (SVM) is used to exploit the 10-m spectral bands among Sentinel-2 bands of three resolutions (10-m; 20-m; 60-m). The new Multi-Spectral Water Index (MuWI), consisting of the complete version and the revised version (MuWI-C and MuWI-R), is designed as the combination of normalized differences for threshold stability. The proposed method is assessed on coincident Sentinel-2 and sub-meter images covering a variety of water types. When compared to previous water indexes, results show that both versions of MuWI enable to produce native 10-m resolution water maps with higher classification accuracies (p-value < 0.01). Commission and omission errors are also significantly reduced particularly in terms of shadow and sunglint. Consistent accuracy over complex water mapping scenarios is obtained by MuWI due to high threshold stability. Overall, the proposed MuWI method is applicable to accurate water mapping with improved spatial resolution and accuracy, which possibly facilitates water mapping and its related studies and applications on growing Sentinel-2 images. View Full-Text
Keywords: MuWI; Sentinel-2; multi-spectral water index; water index; NDWI; MNDWI; AWEI; machine learning; SVM; OSH; water mapping; water classification; Landsat; sunglint; shadow MuWI; Sentinel-2; multi-spectral water index; water index; NDWI; MNDWI; AWEI; machine learning; SVM; OSH; water mapping; water classification; Landsat; sunglint; shadow
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MDPI and ACS Style

Wang, Z.; Liu, J.; Li, J.; Zhang, D.D. Multi-Spectral Water Index (MuWI): A Native 10-m Multi-Spectral Water Index for Accurate Water Mapping on Sentinel-2. Remote Sens. 2018, 10, 1643. https://doi.org/10.3390/rs10101643

AMA Style

Wang Z, Liu J, Li J, Zhang DD. Multi-Spectral Water Index (MuWI): A Native 10-m Multi-Spectral Water Index for Accurate Water Mapping on Sentinel-2. Remote Sensing. 2018; 10(10):1643. https://doi.org/10.3390/rs10101643

Chicago/Turabian Style

Wang, Zifeng; Liu, Junguo; Li, Jinbao; Zhang, David D. 2018. "Multi-Spectral Water Index (MuWI): A Native 10-m Multi-Spectral Water Index for Accurate Water Mapping on Sentinel-2" Remote Sens. 10, no. 10: 1643. https://doi.org/10.3390/rs10101643

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