光達資料在臺灣海岸地形變遷上的應用
No Thumbnail Available
Date
2009-06-01
Journal Title
Journal ISSN
Volume Title
Publisher
中華民國航空測量及遙感探測學會
Abstract
光達技術生產的高精度數值地形模型，是監測海岸地形變遷的利器。我國已於近年引進光達技術，雖然尚未建置專為海岸監測而產製的規範，但所生產之高精度DTM，仍為海岸變遷研究的寶貴資料，須善加利用。本文回顧國際上如何應用光達資料在海岸變遷研究上，討論臺灣早期圖資中哪些可能和光達資料套疊比對，並以淡水河口南岸八里海岸為樣區，透過實作探討光達資料在監測海岸地形變遷上，有哪些限制或需注意之處。本研究結合1980年代之1:1000海岸像片地形圖和既有之光達資料，並以高程濱線指標為濱線定義，進行濱線變化及地形變化量的探討。比對結果顯示，該段海岸濱線位置在這20年期間，有53-65公尺不等的變動量。以兩種資料直接或間接生產之DTM，套疊進行地形起伏變化量時，則需特別注意因兩種資料的測量、製作方式不同，所產生的問題。簡而言之，臺灣海岸現有光達資料雖然大多只有一期，但應可和海岸像片地形圖或現場實測斷面所生產的DTM進行套疊比對，量化海岸地形之變遷量。展望未來，筆者期盼政府相關單位應儘速建置濱線製圖(shoreline mapping)的規範，包括從現場拍攝、資料生產到濱線指標的訂定，才可能為建立海岸地形(或濱線)變遷監測，奠定堅實的基礎。
LiDAR is a very useful tool on monitoring coastal geomorphic change and has been introduced into Taiwan in recent years. For making the best use of the LiDAR-derived data on long-term coastal change in Taiwan, this research intends to reveal the possibility and limitation of overlapping LiDAR-derived DTM with preexisting pictorial materials, in particular Orthophoto Base Map in the coastal area (OBMC, scale 1:1000, published in 1980s). The study area is the Bali coast, located to the south of the Dan-shui River mouth.Two types of LiDAR data, provided by Central Geological Survey, MOEA, - LAS file and 2m DTM were used, and 1-meter contour line was adopted as the datum-based shoreline indicator. DTM were also constructed by interpolating contour lines of Orthophoto Base Map. Results show that to combine these two sets of pictorial materials to detect shoreline change and calculate volume change of beach and sand dunes is practicable. The amount of shoreline change is from 53 m to 65 m over two decades along the study area. Many details should be taken into account, however, when detecting volume change of beach/sand dune due to the different resolution and accuracy of the two sets of data.So far, most pictorial materials in Taiwan are not produced for the sea shore zone in purpose, and cause many problems on shoreline mapping work. Thus, it is expected that the authority can set up standards and/or guidelines of shoreline mapping (including LiDAR) in the near future.
LiDAR is a very useful tool on monitoring coastal geomorphic change and has been introduced into Taiwan in recent years. For making the best use of the LiDAR-derived data on long-term coastal change in Taiwan, this research intends to reveal the possibility and limitation of overlapping LiDAR-derived DTM with preexisting pictorial materials, in particular Orthophoto Base Map in the coastal area (OBMC, scale 1:1000, published in 1980s). The study area is the Bali coast, located to the south of the Dan-shui River mouth.Two types of LiDAR data, provided by Central Geological Survey, MOEA, - LAS file and 2m DTM were used, and 1-meter contour line was adopted as the datum-based shoreline indicator. DTM were also constructed by interpolating contour lines of Orthophoto Base Map. Results show that to combine these two sets of pictorial materials to detect shoreline change and calculate volume change of beach and sand dunes is practicable. The amount of shoreline change is from 53 m to 65 m over two decades along the study area. Many details should be taken into account, however, when detecting volume change of beach/sand dune due to the different resolution and accuracy of the two sets of data.So far, most pictorial materials in Taiwan are not produced for the sea shore zone in purpose, and cause many problems on shoreline mapping work. Thus, it is expected that the authority can set up standards and/or guidelines of shoreline mapping (including LiDAR) in the near future.