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Removal of water‐surface reflection effects with a temporal minimum filter for UAV‐based shallow‐water photogrammetry 下载免费PDF全文
I GD Yudha Partama Ariyo Kanno Motoyasu Ueda Yoshihisa Akamatsu Ryutei Inui Masahiko Sekine Koichi Yamamoto Tsuyoshi Imai Takaya Higuchi 《地球表面变化过程与地形》2018,43(12):2673-2682
The recent development of structure‐from‐motion (SfM) and multi‐view stereo (MVS) photogrammetry techniques has enabled semi‐automatic high‐resolution bathymetry using aerial images taken by consumer‐grade digital cameras mounted on unmanned aerial vehicles (UAVs). However, the applicability of these techniques is sometimes limited by sun and sky reflections at the water surface, which render the point‐cloud density and accuracy insufficient. In this research, we present a new imaging technique to suppress the effect of these water‐surface reflections. In this technique, we order a drone to take a short video instead of a still picture at each waypoint. We then apply a temporal minimum filter to the video. This filter extracts the smallest RGB values in all the video frames for each pixel, and composes an image with greatly reduced reflection effects. To assess the performance of this technique, we applied it at three small shallow‐water sites. Specifically, we evaluated the effect of the technique on the point cloud density and the accuracy and precision of the photogrammetry. The results showed that the proposed technique achieved a far denser point cloud than the case in which a randomly chosen frame was used for each waypoint, and also showed better overall accuracy and precision in estimating water‐bottom elevation. The effectiveness of this new technique should depend on the surface wave state and sky radiance distribution, and this dependence, as well as the applicability to large areas, should be investigated in future research. Copyright © 2018 John Wiley & Sons, Ltd. 相似文献
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一种基于真实身份的BBS系统实名保障技术 总被引:1,自引:0,他引:1
用户身份的真实性一直是BBS系统管理的重要方面之一。采用SAML协议,将跨域单点登录中的认证技术引入到BBS系统中,从而实现了用户采用真实身份登录BBS系统,保证了BBS用户的实名。并以多个高校的BBS系统作为样例,建立起基于真实身份的示范BBS系统。 相似文献
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F.J Cook W Hicks E.A Gardner G.D Carlin D.W Froggatt 《Marine pollution bulletin》2000,41(7-12):319-326
Disturbed acid sulphate soils are potent sources of acidity in coastal waterways. Monitoring studies of the drainage water for sites at East Trinity, Cairns and Pimpama, south-east Queensland indicate that considerable acidity is found in the drainage water from these sites. Hydrogen (H+), ferrous (Fe2+) and aluminium (Al) ions are the dominant acid cations involved. When drainage water is mixed with fresh or marine waters the effect of H+ on acidity generation is immediate. Aluminium can release acidity on hydrolysis, while the oxidation of Fe2+ to Fe3+ both acidifies and removes dissolved oxygen from the water. Strongly acidic waters with low levels of dissolved oxygen concentration are undesirable for most forms of aquatic life. Export of acidity from acid sulphate soil is likely to have a major effect on inshore fisheries and breeding grounds especially in periods of flood following drought or periods of low rainfall, where large volumes of acidity can be flushed/leached into sensitive aquatic/marine habitats. Impacts may include low dissolved oxygen, fish kills, epizootic ulceration syndrome and damage to oysters. During the processes of oxidation and hydrolysis, iron and aluminium flocs form, that can smother benthic communities. Heavy metals are found in the drainage water at elevated levels and may also be of concern for aquatic organisms. Chronic effects such as habitat degradation, mortality of marine worms, bivalves, invasion of acid tolerant species (both plant and animal) and avoidance of habitat have been documented elsewhere. These areas require further research. 相似文献
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Li-Cai Deng Heidi Jo Newberg Chao Liu Jeffrey L. Carlin Timothy C. Beers Li Chen Hsu-Tai Lee Carl J. Grillmair Puragra Guhathakurta Zhan-Wen Han Jin-Liang Hou Sebastien Lepine Jing Li Xiao-Wei Liu Kai-Ke Pan J. A. Sellwood Bo Wang Hong-Chi Wang Fan Yang Brian Yanny Hao-Tong Zhang Yue-Yang Zhang Zheng Zheng Zi Zhu 《天体物理学报》2012,(7):735-754
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Jeffrey L. Carlin Sebastien Lepine Heidi Jo Newberg Li-Cai Deng Timothy C. Beers Yu-Qin Chen Norbert Christlie Xiao-Ting Fu Shuang Gao Carl J. Grillmair PuragraGuhathakurta Zhan-Wen Han Jin-Liang Hou Hsu-Tai Lee Jing Li Chao Liu Xiao-Wei Liu Kai-Ke Pan J. A. Sellwood Hong-Chi Wang Fan Yang Brian Yanny Yue-Yang Zhan Zheng Zheng Zi Zhu 《天体物理学报》2012,(7):755-771
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High hydrogen pressure pyrolysis (hydropyrolysis) was performed on samples of solvent extracted Kimmeridge Clay Formation
source rock with a maturity equivalent to ca. 0.35% vitrinite reflectance. We describe the types and distributions of organic nitrogen compounds in the pyrolysis products
(hydropyrolysates) using GC-MS. Compounds identified included alkyl-substituted indoles, carbazoles, benzocarbazoles, quinolines
and benzoquinolines. The distributions of the isomers of methylcarbazoles, C2-alkylcarbazoles and benzocarbazoles in the hydropyrolysates were compared to a typical North Sea oil. The hydropyrolysates
compared to the North Sea oil, showed increased contributions from alkylcarbazole isomers where the nitrogen group is "exposed"
(no alkyl substituents adjacent to the nitrogen functionality) and appreciable levels of benzo[b]carbazole relative to benzo[a]- and benzo[c]carbazoles. Hydropyrolysis is found to be an ideal technique for liberating appreciable quantities of heterocyclic organic
nitrogen compounds from geomacromolecules. The products released from the immature Kimmeridge Clay are thought to represent
a potential source of nitrogen compounds in the bound phase (kerogen) able to contribute to the free bitumen phase during
catagenesis. 相似文献
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