An automatic tidal flat extraction algorithm for the Bohai Bay incorporating irregular hexagonal grid

doi:10.13474/j.cnki.11-2246.2026.0809

Abstract

Abstract: [Purposes] To improve the accuracy of tidal flat extraction in complex environments，this study proposes a tidal flat extraction algorithm that incorporates an irregular hexagonal grid (IHG). [Methods] Firstly，the algorithm uses a time-series remote sensing image dataset to generate extreme tidal level images based on the modified normalized difference water index (mNDWI)via the maximum spectral index composite (MSIC)method.Then，through an adaptive threshold gridding strategy，the study area is divided into independent hexagonal units，and the Otsu algorithm is applied to achieve fully automatic extraction of tidal flats in the Bohai Bay in 2023. [Findings] Experiments show that the MSIC-Otsu-IHG algorithm reduces the misclassification of confusing land cover types such as salt pans and suspended sediment.Compared with the MSIC-Otsu algorithm，the overall classification accuracy is improved by 8.4%，and the Kappa coefficient increases from 0.63 to 0.86.When comparing the tidal flat extraction results from two types of images，the overall accuracy and Kappa coefficient of Sentinel-2 data reach 93.60% and 0.86，respectively，which are superior to those of Landsat 8 (89.60% and 0.79). [Conclusions] The MSIC-Otsu-IHG algorithm not only effectively improves the accuracy of land cover separation but also exhibits good applicability in both medium and high spatiotemporal resolution images，providing methodological support for the automatic and refined extraction of tidal flats．

Key words: tidal flat extraction, irregular hexagonal grid, adaptive threshold gridding, MSIC-Otsu algorithm, Bohai Bay

CLC Number:

P237

Zhang Xue, Zhang Shuyuan, Zhang Zhijie, He Junliang, Song Kunlun, Qi Qing, Zhang Miaomiao, Zhang Xiao. An automatic tidal flat extraction algorithm for the Bohai Bay incorporating irregular hexagonal grid[J]. Bulletin of Surveying and Mapping, 2026, 0(8): 59-66.

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URL: http://tb.chinasmp.com/EN/10.13474/j.cnki.11-2246.2026.0809

http://tb.chinasmp.com/EN/Y2026/V0/I8/59

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