Department of Geography, University of Gour Banga, Malda, India.
Environ Sci Pollut Res Int. 2023 Sep;30(41):94485-94500. doi: 10.1007/s11356-023-29027-1. Epub 2023 Aug 3.
Research on investigating spatial resolution effect on image-based wetland mapping was done, and reported finer resolution is more appropriate. But is Sentinel image more effective than Landsat image for delineating ox-bow lake, a cut-off channel of a river, and for mapping inundation frequency? Inundation frequency means regularly, water appears in a pixel. In order to obtain these answers, the present study used frequently used spectral indices like normalized difference water index (NDWI), modified NDWI (MNDWI), re-modified NDWI (RmNDWI) and ensemble vegetation inclusive aggregated water index (ViAWI). For obtaining inundation consistency character, the water presence frequency (WPF) approach was adopted. A set of accuracy matrices was applied for validating the resolution effect. Results revealed that among the used indices, MNDWI was found suitable for ox-bow lake mapping. But this index is not able to map vegetated part of the ox-bow lakes. This problem was resolved using ensemble ViAWI. Inundation frequency analysis exhibited that about 70% of the area is consistent with water presence and therefore is hydro-ecologically and economically viable, and no such major differences were recorded between Sentinel and Landsat images. The study further revealed that finer resolution Sentinel images are more effective in ox-bow lake mapping and characterising inundation frequency, but they were not significantly better. Accuracy difference between them was found at the very minimum. Therefore, the study recommended that in a Sentinel image sparse condition, Landsat images could alternatively be used without much accuracy departure, particularly on those water bodies where water appearance is not highly erratic.
本研究使用了常用的光谱指数，如归一化差异水体指数（NDWI）、改进的 NDWI（MNDWI）、再改进的 NDWI（RmNDWI）和综合植被含水综合指数（ViAWI），以调查基于图像的湿地制图中空间分辨率效应的研究，并报告更精细的分辨率更合适。但是，对于描绘牛轭湖（河流的一个断流河道）和绘制淹没频率，Sentinel 图像是否比 Landsat 图像更有效？淹没频率是指定期出现水的像素。为了获得这些答案，本研究使用了常用的光谱指数，如归一化差异水体指数（NDWI）、改进的 NDWI（MNDWI）、再改进的 NDWI（RmNDWI）和综合植被含水综合指数（ViAWI）。为了获得淹没一致性特征，采用了水出现频率（WPF）方法。本研究应用了一套精度矩阵来验证分辨率效应。结果表明，在所使用的指数中，MNDWI 适合于牛轭湖的制图。但是，该指数无法绘制牛轭湖的植被部分。这个问题通过使用综合的 ViAWI 得到了解决。淹没频率分析表明，约 70%的区域与水的存在一致，因此在水生态和经济上是可行的，并且在 Sentinel 和 Landsat 图像之间没有记录到重大差异。研究进一步表明，更精细的分辨率 Sentinel 图像在牛轭湖制图和描述淹没频率方面更有效，但它们并没有显著更好。它们之间的精度差异非常小。因此，本研究建议在 Sentinel 图像稀疏的情况下，可以使用 Landsat 图像代替，而不会有太大的精度偏差，特别是对于那些水出现不太频繁的水体。
