| Summary: | 碩士 === 國立彰化師範大學 === 地理學系 === 106 === Coastal areas are highly dynamic and sensitive, vulnerable to the coastal processes and other natural and human-induced causes. It is fundamental to monitor the evolution of coastal landscape and to understand their dynamic and complex of coastal geomorphological system. The advances in unmanned aerial vehicles (UAV) and photogrammetry provide an effective approach to produce accurate, high spatiotemporal resolution DTMs. In this study, we used UAV photogrammetry to survey the topography change in the Jebel Spit in Penghu, the largest spit landscape in Taiwan. The survey was taken at June 2017, August 2017, and May 2018. We used the Pix4Dmapper, a photogrammetry software, to generate high resolutions DSMs. By comparing the DSMs and sampling the grain size of the spit, we illustrated the topography change spatial-temporal aspects and its linkage to the wave and tidal processes. The results show that the optimum accuracies of DSMs were 1 cm and 2 cm in horizontal and vertical directions, respectively, and have ground resolution of 0.8 cm. By comparing the DSMS the topography has 41.1cm of deposition during typhoon season and has 40.9 cm of erosion during northeast monsoon season. Beach surface shows an annually mass balance between the deponition of typhoon and ersion of northeast monsoon. Northeast monsoon plays an erosive role in the intrusion and sedimentation of the spit, and is closely linked to the change of the monsoon direction, the direction of the dominant sediment transport and the surrounding shore platform. As a whole, the UAV photogrammetry can effectively monitor the coastal topographical changes, and the use of high spatial resolution DSM and orthophoto can help understand the changing characteristics of coastal micro-topography.
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