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1.
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
2.
Ariake Bay, Kyushu Island, has recently exhibited environmental degradation in the form of red tides and anoxic bottom water.
To determine the characteristics and regional classification of the copepod community, zooplankton surveys were made throughout
the bay in three cruises each in October 2004, January 2005 and March 2009 by vertical tows of a 0.1-mm-mesh plankton net.
Oithona davisae was the most abundant in January and March, and Microsetella norvegica in October. Cluster analysis revealed that the copepod community from each cruise was generally separated into the inner
to eastern-middle region and the western-middle to mouth region. A SIMPER analysis revealed that dissimilarity between the
groups and similarity within each group were mainly due to the dominant species, but the similarities within the outer-region
group in January and March were mostly contributed by Paracalanus parvus s.l. A non-metric multidimensional scaling with bubble plots of environmental variables and a BIOENV analysis showed that
transparency was more different between the two groups than temperature and salinity. As compared with two similarly sized,
eutrophic bays (Tokyo and Osaka Bays), Ariake Bay differs from Tokyo Bay in the dominance of M. norvegica and from Osaka Bay in the high abundance of O. davisae even in the colder season. The dominant species and the regional classification of the copepod community in the bay were
similar to those in the studies in the 1970s, suggesting that the copepod community has not notably changed during the last
3 decades. 相似文献
3.
Cheol-Hee Kim Lim-Seok Chang Jeong-Soo Kim Fan Meng Mizuo Kajino Hiromasa Ueda Yuanhang Zhang Hye-Young Son Youjiang He Jun Xu Keiichi Sato Chang-Keun Song Soo-Jin Ban Tatsuya Sakurai Zhiwei Han Lei Duan Suk-Jo Lee Shang-Gyoo Shim Young Sunwoo Tae-Young Lee 《Asia-Pacific Journal of Atmospheric Sciences》2011,47(4):399-411
Three comprehensive acid deposition models were used to simulate the sulfur concentrations over northeast Asia over the period covering entire year of 2002, and discussed the aggregated uncertainties and discrepancies of the three models. The participating models are from the countries participating in the project of Longrange Transboundary Air Pollutants in Northeast Asia (LTP): China, Japan and Korea. The Eulerian Model-3/CMAQ (by China), Regional Air Quality Model (RAQM, by Japan), and Comprehensive Acid Deposition Model (CADM, by Korea) were employed by each country with common emissions data established by the administrative agencies of China, Japan and Korea. The episodic simulation results between 1 to 15, March 2002 are also presented, during which aircraft measurements were carried out over the Yellow sea. The episodic results show both a wide short-term variability in simulations against measurements, and maximum concentration differences of 3~5 times among the three models, requiring that further attention before confidence among the three models can be claimed for short-term simulations. However, the year-long cumulative simulations showed almost the same general features, with lower aggregated uncertainties between the three models, produced by the long term integration over northeast Asia. 相似文献
4.
Mixing states of cloud interstitial particles between water-soluble and insoluble materials apparently differ under various cloud-forming conditions. To study the mixing states of cloud interstitial particles, we made observations at Mt. Tateyama, Japan (2300 m a.s.l.) during June 2007 using fog (> 10 μm)-cut inlets. Number concentrations of dried particles (0.3–0.5 μm diameter) selected for less-grown (LG) particles (particles smaller than 0.56 μm diameter at 88% relative humidity) were used to quantify tendencies of the growth characteristics of cloud interstitial particles. Size-segregated soot mass concentrations (< 0.4 and < 1.1 μm) were also measured for cloud interstitial particles. Three samples of cloud interstitial LG particles at 88% RH were investigated for water-soluble and insoluble components using dialysis (extraction) of water-soluble materials with transmission electron microscopy (TEM). For one TEM sample with high fractions of the LG particles and high soot mass concentrations under high precipitation (2–6 mm/h), most particles (0.1–0.5 μm) were found to be water insoluble. More than half of the water-insoluble particles were considered to be soot particles showing chain aggregations of electron-opaque spherules. Regarding the other two TEM samples with low fractions of the LG particles under less intense precipitation (ca. 1 mm/h), most particles were partly water soluble. The scavenging process in the precipitating cloud can change the population of particles left behind, preferentially leaving insoluble particles according to cloud formation conditions. 相似文献
5.
6.
Marked fluctuation of concentrations of90Sr and137Cs was observed in the bottom waters at the entrance of Wakasa Bay during 1987–1992, and the cause was investigated. The concentrations of90Sr and137Cs in the bottom waters were significantly low when the upper level of the Japan Sea Proper Water (JSPW) was high and covered the sampling depth, but high when the upper level of the JSPW was low. The cause of the fluctuation observed in the bottom waters is, therefore, suggested to be the vertical fluctuation of the upper level of the JSPW on the shelf slope, which has been little described before. 相似文献
7.
Motoyasu Miyata 《Journal of Oceanography》1979,35(1):43-46
A theory of the coastal Kelvin wave is presented in which the pressure is assumed not to be hydrostatic. The results show that the non-hydrostatic Kelvin wave is dispersive and that the e–1 decay distance of the wave amplitude from the coast decreases as the wave length becomes shorter. Similar conclusions can be drawn on the equatorial Kelvin wave. 相似文献
8.
The contents of major and some of the minor elements, nickel, cobalt, copper, zinc and lead were studied on sediments collected from three inlets of Nanao Bay located at eastern side of Noto Peninsula. Little variation was found on the average contents of silicon, iron, titanium, aluminum, manganese, magnesium and potassium among the sediments of West, South and North Bays in Nanao Bay. Whereas significant difference was found on the contents of calcium, chlorine, sulfur and nitrogen among sediments of three bays.As to the minor elements, the average contents of nickel (20±5 ppm), cobalt (5±1 ppm), copper (18±5 ppm) and lead (17±8 ppm) are relatively low but zinc content is high in these sediments comparing with those of coastal deposit around Japan Island. From the results obtained here, it became clear that no environmental contamination of nickel, cobalt, copper and lead, and a little organic pollution were found in Nanao Bay sediments. 相似文献
9.
Landslides - Centrifuge model tests on slopes subject to shaking and rainfall have been performed to examine the response of slopes with shaking-induced cracks to subsequent rainfall and evaluate... 相似文献
10.
Masanori Iye Tatsuo Ueda Masafumi Noguchi Shinko Aoki 《Astrophysics and Space Science》1983,89(2):363-376
A new scheme has been devised to calculate discrete unstable global shearing spiral modes of gaseous disk models of galaxies. The scheme makes use of the Legendre expansion of eigen functions and the problem of stability analysis is reduced to an eigenvalue problem of an infinite matrix. The spiral patterns of these shearing wave solutions of linearized equations change their form in the course of time due to the differential rotation of the equilibrium disk. These shearing wave solutions are presumed to have intermediate characteristics between so-called density-waves and material arms. Comparison between these shearing modes and the non-shearing normal modes for a series of disk models is presented. 相似文献