Search

The LiDAR sensor mounted on a UAV becomes a new powerful tool for geoinfomatic technology. We integrate autonomous unmanned helicopter Pulse Aerospace Vapor 55, carrying Riegl VUX-1 UAV LiDAR with Trimble Applanix AP20 for surveying missions. In this study, we applied the instruments for three regions for different purposes, including bore sight and lever arm parameter determination, and for multiple flight missions tests. Based on the drone and instrument capacity, adapted with the terrain landform and topographic elevation changes, the optimal drone mission planning and scanning parameters are thus assigned, thus capable to acquire dense point clouds higher than 159 points/m^2 in nadir direction within single fly line. To access the dataset, several software packages are used, including: the Trimble Applanix POSPac Mobile Mapping Suite software, GNSS-Aided Inertial post-processing for georeferencing data collected from UAS LiDAR. The Riegl RiPROCESS designed for managing, processing, analyzing, and visualizing and data export for the data acquired based on Riegl Laser Scanners. And finally, access and evaluate the dataset by means of Riegl RiPROCESS and TerraMatch softwares for managing, processing, especially for fly-line adjustment and classification the UAS LiDAR point clouds, so as to compare the UAS dataset with the airborne's. The study tries to evaluate the parameters for fully-automatic point cloud classification by TerraScan, which is used regularly in Taiwan. This study analyzes the influence and efficiency of different parameters for point cloud classification, to separates the ground point from the all point so as to construct the digital elevation model. Finally, the averaged point clouds density of the all and the ground point are higher than 400 and 25 points/m2, respectively. Thus the spatial resolution of digital elevation model (DEM) is about 20 by 20cm. Compared with the data points measured from site surveying, ground control points and check points by means of e-GNSS, RTK (real time kinematic GPS survey) and total station etc., the elevation errors is less than five centimeters; thus the high resolution and high precision digital terrain models (DTMs) are capable to construct. UAS LiDAR point cloud after instrument calibration and flight trajectory adjustment, the surveying data acquisition can achieved as centimetric precision. According to the results, the technology of UAS LiDAR is capable and suitable for high resolution geoinfomatic data acquisition and for multi-disciplinary applications. [ABSTRACT FROM AUTHOR]

Taiwan is among the activest neotectonic place in the World as it is the result of the rapid collision of both Eurasian and Philippine Sea Plates, with an annual average convergence rate of more than 9cm.y-1. This active tectonic shortening generates the Taiwan relief which is characterized by two major mountain ranges: (1) the metamorphic Central Range from Eurasian continental origin, and (2) the eastern Coastal Range characterized by a volcanic Philippine Sea Plate affinity. In between both runs the crustal suture so-called the Longitudinal Valley Fault (LVF), 125km long and N020°E trending, which presents both inter-seismic (Champenois et al., 2013) and earthquake seismic crisis. Effectively it has been affected by 7 earthquakes (EQ) of magnitude larger than 5 within 43 days during the last 70 years: Oct.22, 1951 in Hualien M7.1-7.3, Nov25, 1951 in Chihshang M6.1 and in Yuli M7.3, Dec5, 1951 in Taitung M5.8, see Central Weather Bureau, 1952, or May20 1986 M 6.2 in Hualien, 2003 Mw6.8 in Chengkung, 2006 Mw5.9 in Taitung, 2013 Ruisui EQ, Feb.6 2018 Mw 6.4 Hualien EQ. Consequently, the detailed study of this major active seismic plate suture zone is a major concern for any Taiwan citizens.We herein settle an UAS survey above the Longitudinal Valley Fault zone and the Lichi Melange (W part of the Coastal Range - E. Taiwan) and acquired 17483 high resolution photographs through 2 drones flying at 350 meters above ground level height, by total 23 flight missions, covering a total area of 195km2. After classical photogrammetric processing, we calculate the high resolution Digital Terrain Model (HR-DTM) of the studied area, (with a 10cm planimetric resolution and below 40cm vertical accuracy) and its immediate surroundings along a "buffer" zone of 2.5km. This UAS HR-DTM enables us through classical morphostructural interpretation to up-date the pre-existing geological map (e.g. CGS geological maps, Lin et al., 2009 ; Shyu et al., 2005, 2006, 2007, 2008) into much details. Moreover we mapped into much details also the tectonics structures of the Longitudinal Valley Fault and their evolution. Moreover, we use and combine this morphostructural interpretation with levelings, GPS and PSInSAR datasets (Champenois 2011, and Champenois et al., 2013) in order (1) to locate the active tectonic structures (faults and folds); (2) to characterize those using also field studies; and (3) to quantify them with various complementary geodetic measurements (e.g. Yu et al., 1997; Lee et al., 2008; Hsu et al., 2009; Huang et al., 2010, Zhang et al. 2018).Moreover, several Sea cruises where settled North of the LVF and the Coastal Range in the Hualien vicinity order to extend tectonic structures at sea and better study the onshore/offshore geodynamic transition. They highlights deposits affected in a complex structural geometry which we interpret in the lights of both tectonic inversion associated with major landslides processes (Hsu S.-K., Lin L.-K., work in progress). [ABSTRACT FROM AUTHOR]

Despite numerous recent works (Zhang et al., 2014, Giletycz et al. 2015A and B, 2017; Deffontaines et al., 2016, 2017/2018; Huang et al., 2018), the Hengchun Peninsula (S.Taiwan) remains still poorly known in terms of geodynamic and geomorphological processes. Contrasting results and opposite conclusions are emitted by those previous works in terms of active uplift/subsidence locations, and dealing with the location of the Hengchun and Kenting active faults that definitely needs a much better regional comprehension in order to understand the geodynamic of the outcropping southern tip of the Taiwan Central Range.Two new high resolution datasets (1) the UAS Digital Terrain Model (<10cm ground resolution and <40cm vertical accuracy) and (2) displacements processed from PSInSAR techniques (modified from J.Champenois, 2011, Deffontaines et al. 2017, 2018) that are validated by some GPS fixed stations, lead us to up-date the Hengchun Peninsula geological mapping. The latter had been validated in the fields and the added PSInSAR lead us to determine the active interseismic structures (active faults and folds) during the monitoring time period taking into account even small magnitude of displacements. Special attention where focussed on the location, characterization and quantification of the Hengchun, Kenting and Manchou Faults and their associated active folds that affect the whole Hengchun Penisula.Moreover South to the Hengchun Peninsula, offshore high resolution bathymetric data sets acquired offshore (Chang K.-J. et al., 2015) and E-W transverse seismic reflection profiles (Liu C.-S., and Hsu H.-H., work in progress) lead us to propose an up-dated and integrated onshore/offshore geodynamic model of the whole Hengchun Penisula and clarify its recent evolution. Definitely, this area remains a major Natural Hazards sensitive area as the still active Taiwan Nuclear Power Plant N°3 is situated so close to the Hengchun Fault.References: Champenois, J., 2011: Caractérisation des déformations tectoniques intersismiques de l'île de Taiwan par interférométrie radar, Geophysics, Université Paris-Est, 244 pp., 2011 (some parts in French).Chang, C. P., et al., 2009: Polyphase deformation in a newly emerged accretionary prism: Folding, faulting and rotation in the southern Taiwan mountain range, Tectonophysics, 466, 395–408.Deffontaines, B., et al.: 2016. Structure and deformation of the Southern Taiwan accretionary prism: The active submarine Fangliao Fault Zone offshore west Hengchun Peninsula, Tectonophysics, 692, 227–240, https://doi.org/10.1016/j.tecto.2016.11.007, 2016.Deffontaines B., et al., 2017 discussion paper, doi:10.5194/nhess-2017-55. and 2018: Active tectonics of the onshore Hengchun Fault using UAS DSM combined with ALOS PS-InSAR time series (Southern Taiwan), Nat. Hazards Earth Syst. Sci., 18, 829–845, 2018https://doi.org/10.5194/nhess-18-829-2018.Giletycz, S.J., 2015A: Landscape dynamics of the Hengchun Peninsula, Southern Taiwan. PhD dissertation, National Central University, Chungli, Taiwan, 184 pp., 2015.Giletycz, S.J., et al. 2015B. Transient fluvial landscape and preservation of low-relief terrains in an emerging orogen: exemple from Hengchun peninsula, Taiwan. Geomorphology 231, 169–181.Giletycz, S.J., et al., 2017: Tectonophysics, http://dx.doi.org/10.1016/j.tecto.2017.10.018Huang, C.Y., et al.,2006. Temporal and spatial records of active arc-continent collision in Taiwan:A synthesis. Geological Society of America Bulletin 118(3/4), 274-288. Zhang, X.C., et al., 2014. Provenance analysis and its geological significance to the Miocene accretionary prism of Hengchun Peninsula, southern Taiwan. Journal of Asian Earth Sciences 85, 26-39. [ABSTRACT FROM AUTHOR]