• Journal of Cadastre & Land InformatiX
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• v.52 no.1
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• pp.69-80
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• 2022

Drone photogrammetry generally acquires images vertically or obliquely from above, so when photographing for the purpose of three-dimensional modeling, image matching for the ground of a building and spatial accuracy of point cloud data are poor, resulting in poor 3D mesh completeness. Therefore, to overcome this, this study analyzed the spatial accuracy of each drone image by acquiring smartphone images from the ground, and evaluated the accuracy improvement and completeness of 3D mesh when the smartphone image is not combined with the drone image. As a result of the study, the horizontal (x,y) accuracy of drone photogrammetry was about 1/200,000, similar to that of traditional photogrammetry. In addition, it was analyzed that the accuracy according to the photographing method was more affected by the photographing angle of the object than the increase in the number of photos. In the case of the smartphone image combination, the accuracy was not significantly affected, but the completeness of the 3D mesh was able to obtain a 3D mesh of about LoD3 that satisfies the digital twin city standard. Therefore, it is judged that it can be sufficiently used to build a 3D model for digital twin city by combining drone images and smartphones or DSLR images taken on the ground.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.5
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• pp.479-493
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• 2016

LiDAR(Light Detection and Ranging) data acquired from ALS(Airborne Laser Scanner) has been intensively utilized to reconstruct object models. Especially, researches for 3D modeling from LiDAR data have been performed to establish high quality spatial information such as precise 3D city models and true orthoimages efficiently. To reconstruct object models from irregularly distributed LiDAR point clouds, sensor calibration, noise removal, filtering to separate objects from ground surfaces are required as pre-processing. Classification and segmentation based on geometric homogeneity of the features, grouping and representation of the segmented surfaces, topological analysis of the surface patches for modeling, and accuracy assessment are accompanied by modeling procedure. While many modeling methods are based on the segmentation process, this paper proposed to extract key points directly for building modeling without segmentation. The method was applied to simulated and real data sets with various roof shapes. The results demonstrate feasibility of the proposed method through the accuracy analysis.

• International Journal of Highway Engineering
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• v.16 no.2
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• pp.43-52
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• 2014

PURPOSES : To solve problems in current compaction control DCPT(Dynamic Cone Penetrometer Test), highly correlated with various testing methods, simple, and economic is being applied. However, it、s hard to utilize DCPT results due to the few numerical analyses for DCPT have been performed and the lack of data accumulation. Therefore, this study tried to verify the validation of numerical modeling for DCPT by comparing and analyzing the results of numerical analyses with field tests. METHODS: The ground elastic modulus and PR(Penetration Rate) value were estimated by using PFC(Particle Flow Code) 3D program based on the discrete element method. Those values were compared and analyzed with the result of field tests. Also, back analysis was conducted to describe ground elastic modulus of field tests. RESULTS : Relative errors of PR value between the numerical analyses and field tests were calculated to be comparatively low. Also, the relationship between elastic modulus and PR value turned out to be similar. CONCLUSIONS : Numerical modeling of DCPT is considered to be suitable for describing field tests by carrying out numerical analysis using PFC 3D program.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.347-352
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• 2007

Recently, automated construction machines have been developed for technically solving construction industry problems such as labor, productivity, quality and the profit decrease. In domestic construction industry, a research for developing an intelligent excavation robot has been performed. The primary objective of this research is to analysis state-of-the art technologies in order to recognize local ground shape in real-time and compute soil volume of earth moving. This research analyzed five elemental technologies for 3D modeling of local ground shape and selected an optimal technology among the five technologies through using AHP method. It is anticipated that the optimal technology selected for 3D modeling of local ground shape can be effectively used to develop the intelligent excavation robot.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.1
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• pp.59-65
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• 2018

The object of this paper was to analyze combined load acting on agricultural reservoir. This study was carried out to 3-D numerical modeling for displacement characteristic and seismic acceleration characteristic. The results of study were analyzed and summarized as follow. It was found that the displacement caused by combined load acting on railway and agricultural reservoir did not reflect the effect of load and the seismic wave consistently. The ground accelerations that occur in railway and dam were amplified because 3-D numerical analysis program interprets ground as an elastic body. Actual ground shows characteristics of elasticity and plasticity, so measured values will show different tendency. As a result of analyzing displacement characteristics, it is considered to be related to stiffness. The Ofunato seismic wave, the displacement (77.1 mm) of the body satisfied the allowable displacement (220 mm), but The Hachinohe seismic wave (282.8 mm) did not. It is considered that displacement caused by combined load is affected not only by acceleration but also by characteristics of materials.

• Korean Journal of Geomatics
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• v.2 no.1
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• pp.31-35
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• 2002

This paper describes an experiment for three-dimensional positioning for a pair of KOMPSAT stereostrips using the ancillary data and a single ground control point. The photogrammetric model for three-dimensional positioning was performed as follows: first, initialization of orbital and attitude parameters derived from ancillary data; second, adjustment of orbital and attitude parameters for the satellite to minimize the ground position error with respect to a GCP using the collinearity condition; third, determination of actual satellite position; and lastly, space intersection. This model was tested for a pair of stereo strips with 0.6 base-to-height ratio and GCPs identified from a 1:5,000 scale digital map. As the result, the satellite position of offset was corrected by only one GCP and the accuracy for the geometric modeling showed 38.89m RMSE.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1047-1053
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• 2017

The range data acquired by 2D/3D LIDAR, a core sensor for autonomous navigation of an unmanned ground vehicle, is effectively used for ground modeling and obstacle detection. Within the ambiguous boundary of a road environment, however, LIDAR does not provide enough information to analyze the traversable region. This paper presents a new method to analyze a candidate area using the characteristics of LIDAR reflectivity for better detection of a traversable region. We detected a candidate traversable area through the front zone of the vehicle using the learning process of LIDAR reflectivity, after calibration of the reflectivity of each channel. We validated the proposed method of a candidate traversable region detection by performing experiments in the real operating environment of the unmanned ground vehicle.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2046-2051
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• 2015

Currently, most high-voltage gas circuit breakers (CBs) include asymmetrical geometries in the shield, the tank, the hot-gas exhaust, and the connection parts for bushings. For this reason, a 3-dimensional (3-D) analysis of the insulation capability is necessary, rather than a 2-D analysis. However, a 3-D analysis has difficulties due to the computational time and complex modeling. This paper presents a 3-D analysis considering the asymmetry in high-voltage gas CBs and a technique to reduce the calculation time. In the proposed technique, the arc plasma requiring the most computational time is first calculated by a 2-D analysis. Then, the results such as pressure, temperature, and velocity are input as a source for the 3-D analysis. This technique is applied to a 145kV self-blast-type CB and the analysis result exhibits good agreement with the experimental result.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.773-775
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• 2003

From the view point of data fusion, we integrate LIDAR data and digital aerial images to perform 3D building modeling in this study. The proposed scheme comprises two major parts: (1) building block extraction and (2) building model reconstruction. In the first step, height differences are analyzed to detect the above ground areas. Color analysis is then performed for the exclusion of tree areas. Potential building blocks are selected first followed by the refinement of building areas. In the second step, through edge detection and extracting the height information from LIDAR data, accurate 3D edges in object space is calculated. The accurate 3D edges are combined with the already developed SMS method for building modeling. LIDAR data acquired by Leica ALS 40 in Hsin-Chu Science-based Industrial Park of north Taiwan will be used in the test.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.129-141
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• 2003

The precise prediction of ground displacement plays an important role in planning and constructing tunnels. In this study, an equation for predicting the surface and crown settlement is suggested by examining the theories of ground movement caused by tunnel excavation. From the 3D numerical modeling, the reinforcement effect of UAM (Umbrella Arch Method) is quantitatively analyzed with respect to deformation modulus and overburden. By using a regression technique for the numerical results, an equation for predicting the settlement is suggested.