Accuracy Assessment of Multi-Temporal Intertidal DEM in Taiwan Using ICESat-2 Ying-Cih Shih(a), Kuo-Hsin Tseng(a,b)
a) Department of Civil Engineering, National Central University, Taiwan
b) Center for Space and Remote Sensing Research, National Central University, Taiwan
Abstract
The steep eastern terrain and gentle western slopes of Taiwan have shaped extensive sandy coastlines and numerous wetlands along the western shore. Situated in a subtropical region with variable climatic conditions, the coastlines are frequently affected by typhoons, tides, and coastal currents, resulting in continual shoreline changes. These factors highlight the importance of timely observation and analysis of intertidal zones. To capture such dynamic changes, this study utilizes Sentinel-2 multispectral imagery from 2018 to 2024 to reconstruct intertidal topography and applies ICESat-2 laser altimetry data to validate elevation accuracy. The objective is to identify the optimal time span for reconstruction and determine the most suitable temporal scale for intertidal monitoring in Taiwan.
The study area is located at the Dadu River Estuary Wetland. ICESat-2 ATL03 point cloud data from June 2020 to January 2024 were collected, with the lowest-tide observation used as the starting point for reconstructing intertidal topography across various time scales. A Modified Normalized Difference Water Index (MNDWI) was first applied to delineate the land-water boundary. Then, inundation probabilities were calculated and combined with tidal models to estimate elevation values. The reconstructed intertidal topography was validated using ICESat-2 elevation profiles. Results show that RMSE values across different observation periods range from 0.3 to 0.7 meters, with optimal accuracy achieved at the nine-month period. These findings demonstrate that the proposed method effectively evaluates reconstruction performance across varying time spans and helps identify the optimal temporal scale for intertidal monitoring in Taiwan, offering valuable guidance for future wetland and coastal management.
