标题: 卫星影像的水线辨识及其应用在外伞顶洲的滩线变迁
Waterline detection from satellite images and its application to the shoreline evolution of Waisanding barrier
作者: 赖羿齐
张宪国
Lai ,Yi-Chi
Chang, Hsien-Kuo
土木工程系所
关键字: 外伞顶洲;滩线变迁;影像处理;水线辨识;边缘侦测;Waisanding barrier;Shoreline evolution;Image processing;Detection of waterline;Edge detection
公开日期: 2017
摘要: 本文提出撷取卫星影像的水线并平移至滩线的方法,并以外伞顶
洲为例,探讨其滩线变迁。影像处理的技巧包括提高多频谱态影像解 析度的 IHS 转换法,区分陆域及海域界线的 NDWI,能提高海陆区域
对比度的影像强化,消除水面波纹及碎波白泡沫的形态学,撷取海陆 交接水线的 Canny 法。因外伞顶洲无潮汐观测资料,本文以潮位资料 融合法配合 NAO.99b 的潮位数值模式,获得外伞顶洲精准的潮位。
透过潮位及实际底床滩面的坡度,本文方法可计算出影像的水线平移
至滩线距离,而可决定滩线位置。在选择断面上平移后滩线与实测滩 线的 RMSE 为 15.40~53.48m 及 Bias 为 0.65~10.2m,都比原本水线的 值分别修正 44%~74%,及 89%~98%,证实本方法的可行性。
应用本文方法探讨外伞顶洲自1994年至2015年间滩线及陆上面
积的变化特性。由分析结果发现外伞顶洲以北端为支点南端逆时针旋
转,未来会陆化与台湾接连,陆上面积长期有缩小的趋势,本文预估 外伞顶洲将于 2062 至 2066 间年全部没入平均海平面以下。然而,外
伞顶洲的陆地面积在夏季是增加的而冬季减少,有季节性的变化特 性,此满足 Sunamura and Horikawa(1974) 判断海滩剖面的分类。
Image processing of detecting waterline in satellite images and waterline-to-shoreline shifting method were proposed in this thesis and its application to investigating shoreline evolution and variation of land area of Waisanding barrier. The image processing includes (1) IHS conversion method for improving the resolution of multi-spectral image (2) NDWI index for determining possible interface of land and sea zones (3) Image enhancement method for improving the contrast between land and sea (4) Morphology for eliminating optional spots such as white ripples of breakers (5) Canny edge detection for capturing the waterline. Due to no observation on tides at Waisanding barrier data blending method associated with NAO.99b tidal model is used to compute the accurate tidal levels. By the trigonometry the obtained tidal level and beachface slope lead to a horizontal distance for shifting the waterline to the shoreline, of which the position is thus determined. RMSEs, Root Mean Square Error, between the shifted shoreline and the measured shoreline at different profiles are evaluated to be 15.40 - 53.48 m and the corresponding Biases are 0.65 - 10.2 m. The values are much


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smaller than those between the waterline and the measured shoreline at the same profiles. Modification on RMSE and Bias using the determined shoreline improves by 44% - 74% and 89% - 98%, respectively, rather than using the detected waterline. The proposed method is proven to be applicable.
The shoreline evolution and variations of land area above mean sea level of Waisanding barrier from 1994 to 2015 are investigated using the proposed method. The result shows that southern Waisanding barrier counterclockwise rotates about the southern fixed end. In the near future Waisanding barrier will move and connect to western Taiwan. Meanwhile the dry land of Waisanding barrier has a long-term decreasing trend and possibly disappear during 2062-2066 depending on the linearly fitted rate. The beach of Waisanding barrier suffers from erosion in the winter and accretes in the summer to have a regular and seasonal variations. The result can be explained by the formula for beach types of Sunamura and Horikawa(1974).
URI: http://etd.lib.nctu.edu.tw/cdrfb3/record/nctu/#GT070351250
http://hdl.handle.net/11536/140431
显示于类别:Thesis