以衛星大數據觀察長期國土變遷──以外傘頂洲為例

Observing Long-term Territorial Changes Through Spatial Big Data: A Case Study of Waisanding Sand Bar

本研究利用衛星大數據分析長期的國土變化，針對嘉義東石漁港外的外傘頂洲進行海岸線變遷的觀察與分析。透過衛星影像的判釋與處理，包括邊緣偵測技術，快速識別出外傘頂洲海岸線的變化情況及估計移動距離，本研究以1991年至2021年近三十年的衛星影像資料，估算外傘頂洲區域的變遷及其移動情形。經過三十年的觀測，發現外傘頂洲受波浪、沿岸流及東北季風的影響，正逐漸向西南方向漂移，本研究估計外傘頂洲的移動距離：北端的整體移動距離約為3312公尺，而南端的移動距離則約為3708公尺。
根據長期變化速率的分析，透過空間資訊進行快速估算，發現外傘頂洲的北端每年向西南方向移動約90公尺，南端則向東移動約150公尺，這些變化資訊對於相關單位而言極為重要，應予以充分重視。

This study analyzes the long-term changes in national territory using satellite big data, focusing on the coastal changes of Waisanding sand bar located outside of Dongshi Fishing Harbor. By interpreting and processing satellite imagery, including edge detection, we identify the coastline changes of Waisanding sand bar. We estimate the movement changes of the island's region by observing satellite images from 1991 to 2021 over nearly three decades. Waisanding sand bar, influenced by waves, coastal currents, and the northeast monsoon, is drifting towards the southwest. We have also estimated the displacement of Waisanding sand bar over the past 30 years. The total displacement of the northern part of the island is approximately 3,312 meters, while the southern part has moved about 3,708 meters.
Through the analysis of long-term change rates and rapid spatial information estimation, we found that the top of Waisanding sand bar moves southwestward by about 90 meters per year, while the southern end moves eastward by approximately 150 meters annually. This information is of great importance and should be taken into consideration by relevant authorities.