  Tidal flat topography provides crucial insights for understanding tidal flats
and their dynamic evolution. However, the wide-ranging and rapidly changing
nature of tidal flats, which are periodically submerged in shallow water, pose
challenges for many current monitoring methods in terms of both efficiency and
precision. In this study, we considered the dynamic process of tidal flat
submergence and utilized time-series Sentinel-2 images on Google Earth Engine
(GEE) to calculate the tidal flat exposure frequency. This information was used
to determine the spatial extent of the tidal flats, and subsequently, by
employing ICESat-2 data, we established a 1D-linear regression model based on
elevation and frequency values, which realizes the inversion of the tidal flat
elevation within Cixi City. The study shows the following: (1) the tidal flat
exposure frequency and ICESat-2 elevation data exhibit a strong positive
correlation (R2=0.85); (2) the tidal flat area within Cixi City is 115.81 km2,
and the overall accuracy is 95.36%; and (3) the elevation range of the tidal
flats in the study area is between -0.42 and 2.73 m, and the mean absolute
error (MAE) is 0.24 m. Additionally, we consider that the temporal resolution
of remote sensing imagery plays a crucial role in determining the accuracy of
the elevation inversion, and we found that higher tidal flats exhibit better
inversion accuracy than lower tidal flats.
