- 期刊
應用衛星影像的水線辨識於外傘頂洲的灘線變遷
Shoreline Evolution of the Waisanding Barrier Using Waterline Detection from Satellite Images
摘要
本文提出擷取衛星影像的水線，平移至灘線的方法，並探討外傘頂洲的灘線變遷。研究方法的影像處理技巧包括，IHS轉換法、NDWI、影像強化、形態學及Canny法。另外，修正NAO99b潮位數值模式的潮位資料融合法，來解決外傘頂洲無觀測潮汐資料的問題。自1994至2015年的灘線及陸上面積的長期變化分析後發現，外傘頂洲的海側灘線在北端以-30.5 m/yr，而南端以-119 m/yr的速度往內陸內縮；陸上面積被侵蝕速率近年有增加的趨勢，且長期的變化有夏季增加，但冬季減少的季節特性。若以2009～2015年的陸地面積被侵蝕速率，可預測外傘頂洲的陸地將於2060年完全低於平均潮位而淪為潛沒沙洲。
並列摘要
This paper investigates the shoreline evolution of Waisanding barrier using waterline detection from satellite images. Required image processing includes (1) IHS conversion method (2) NDWI index (3) Image enhancement method (4) Morphology and (5) Canny edge detection for capturing the waterline. Due to no observation on tides at the Waisanding barrier data blending method associated with NAO99b tidal model is used to accurately compute the tidal levels. The horizontal distance to shift the waterline to the shoreline is determined by both obtained tidal level and beachface slope. The shoreline evolution and land-area variation above mean sea level of the Waisanding barrier from 1994 to 2015 are evaluated to show that the northern shoreline of the Waisanding barrier is receding by a rate of 30.5 m/yr and the southern part is by 119 m/yr. The results also indicate that the land area of the Waisanding barrier has a long-term decreasing trend with a faster rate in the recent period and a regular and seasonal variation of erosion in the winter and accretion in the summer. Depending on the decreasing rate of land area from 2009 to 2015 the Waisanding barrier will vanish in 2060 based on the rate.