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大学院国際資源学研究科 |
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Yasuda H.
Journal of Great Lakes Research ( Journal of Great Lakes Research ) 48 ( 2 ) 468 - 477 2022年04月 [査読有り]
研究論文（学術雑誌） 国際共著
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Teleconnection of rainfall time series in the central Nile Basin with sea surface temperature
Yasuda H.
Paddy and Water Environment ( Paddy and Water Environment ) 16 ( 4 ) 805 - 821 2018年10月 [査読有り]
研究論文（学術雑誌） 国際共著
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Construction of Virtual Reality Space of the Tottori Sand Dunes using UAVs
SAITO Tadaomi, KAWAI Takayuki, OKASHITA Kisumi, INOSAKO Koji
沙漠研究 ( 日本沙漠学会 ) 32 ( S ) 187 - 191 2022年12月
<p>The Tottori Sand Dunes, located along Japan’s Sanin Coast, are a UNESCO Global Geopark and a popular tourist attraction with millions of annual visitors. However, the tourism opportunities offered by them are hampered by such problems as severe meteorological conditions and vast, undulating landscapes. Constructing a virtual reality (VR) space might be one solution to these problems. Recently, a technique that combined unmanned aerial vehicles (UAVs or drones) and structure from motion (SfM) photogrammetry has been attracting attention for generating 3D models. The main objective of this paper is to construct a VR space of the Tottori Sand Dunes using 3D models generated from UAVs. Another objective is to examine optimal photography conditions and model generation conditions to create beautiful but small 3D models for the construction of a VR space. Two types of UAVs were used to acquire the image data. Metashape (Agisoft) was used as the SfM software for data processing. A cross-platform game engine called Unity (Unity Software Inc.) was used to construct the VR spaces. VIVE Cosmos (HTC) was employed as a head-mounted display (HMD) with controllers for the VR system. As the results, the VR space was successfully constructed in Unity using a 3D model generated by a combination of UAV techniques and SfM photogrammetry. The optimal photography and model generation conditions were determined and used to generate beautiful 3D models for the construction of a VR space.</p>
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Yasuda H.
Geofizika ( Geofizika ) 39 ( 1 ) 1 - 20 2022年
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Agroecology-based soil erosion assessment for better conservation planning in Ethiopian river basins
Ayele Almaw Fenta, Atsushi Tsunekawa, Nigussie Haregeweyn, Mitsuru Tsubo, Hiroshi Yasuda, Takayuki Kawai, Kindiye Ebabu, Mulatu Liyew Berihun, Ashebir Sewale Belay, Dagnenet Sultan
ENVIRONMENTAL RESEARCH ( ACADEMIC PRESS INC ELSEVIER SCIENCE ) 195 2021年04月
Soil erosion by water is one of the main environmental concerns in Ethiopia. Several studies have examined this at plot and watershed scales, but no systematic study of soil erosion severity and management solutions at national scale is available. This study investigated soil erosion and the potential of land-cover- and agroecology-specific land management practices in reducing soil loss through employing the Revised Universal Soil Loss Equation and the best available datasets. The mean rate of soil loss by water erosion in Ethiopia was estimated as 16.5 t ha(-1) yr(-1), with an annual gross soil loss of ca. 1.9 x 10(9) t, of which the net soil loss was estimated as ca. 410 x 10(6) t (22% of the gross soil loss). Soil loss varied across land cover types, 15 agroecological zones, and 10 river basins, with the main contributors in the respective analyses being cropland (ca. 23% of Ethiopia; 50% of the soil loss; mean soil loss rate of 36.5 t ha(-1) yr(-1)), Moist Weyna Dega (ca. 10%; 20%; 33.3 t ha(-1) yr(-1)), and the Abay basin (ca. 15%; 30%; 32.8 t ha(-1) yr(-1)). Our results show that ca. 25% of Ethiopia (28 x 10(6) ha) has soil loss rates above 10 t ha(-1) yr(-1), which is higher than the tolerable soil loss limits estimated for Ethiopia. Ex-ante analysis revealed that implementation of land-cover- and agroecology-specific land management practices (level bunds, graded bunds, trenches, and exclosures combined with trenches and/or bunds) in such areas could reduce the mean soil loss rate from 16.5 t ha(-1) yr(-1) to 5.3 t ha(-1) yr(-1) (mean, by ca. 68%; range, 65-70%). Suitable land management practices in the Abay and Tekeze basins and Dega and Weyna Dega agroecologies, which experience particularly severe erosion, would account for ca. 50 and 70% of the estimated soil loss reduction, respectively. This study can help raise awareness among policy makers and land managers of the extent and severity of soil loss by water erosion for better conservation planning in river basins to support sustainable use of land and water resources.
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Ground penetrating radar for soil-water measurement in a semi-arid climate in the Orkhon River basin, central Mongolia
Amarsaikhan Tsogtbaatar, Takayuki Kawai, Motoyuki Sato
EXPLORATION GEOPHYSICS ( TAYLOR & FRANCIS LTD ) 2021年04月
In this paper, we present a velocity analysis technique using ground-penetrating radar (GPR) data to estimate near-surface soil-water content affected by topography and solar radiation on a mountain peak, mountain mid-slope, and alluvial plain sites in a semi-arid climate area in central Asia. By making precise measurements of reflected EM wave velocity, the water content in the near-surface soil was determined. The GPR experiments at several frequencies were carried out in two sequential phases (comprising common-offset and multi-offset methods) to obtain the soil-water content and illustrate the subsurface structure. We then tried to determine the relationship between near-surface moisture content and permafrost thawing. Therefore, we used several different methods including time-domain reflectometry and a resistivity survey. We also confirmed via the GPR data that vegetation cover indicates soil-water content in the near-surface soil. The results evaluated in this study provide meaningful information about soil water as well as subsurface structures. The GPR data acquired at the survey sites indicated a large range of near-surface water content due to the topography of the survey lines.
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Influence of polacrylamede application on structure stability of Ethiopian soils
Fujimaki H, Kawai T, Mamedov A.L
10th International congress on the Soil resources and environment conservation 2018年10月 - 2018年10月
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Aerial photogrammetry and three-dimensional modeling of the Tottori sand dune using UAV
Saito, T, Kawai, T, Inosako, K, Yasuda, H
Desert Technology 13 International Conference 2018年03月 - 2018年03月
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Estimation of hydrogeological structure combining groundwater-aeration-sound, ground-penetrating- radar and resistivity tomography in semi-arid area
Takayuki Kawai, Motoyuki Sato, Yasuyuki Tada, Ryota Tsuchiya, Yuki Morinaga, Masato Shinoda, Seiichirou Kuroda, Hiroshi Yasuda
Desert Technology 13 International Conference 2018年03月 - 2018年03月
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NMR and GPR sounding to characterize groundwater aquifer in sand dunes area
Chisato Konishi, Kunio Aoike, Takayuki Kawai, Seiichiro Kuroda
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2017 2017年03月 - 2017年03月