• Journal of the Korean Association of Geographic Information Studies
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• v.4 no.4
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• pp.61-71
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• 2001

In these days, surveying instruments are developing rapidly and the precision is improving continuously. The reappearance of three dimensional terrains of a great precision are possible and the calculation of the area or the volume has a high precision due to the development of the technique of the spatial information system using computer. But actually, in construction site they calculate two-dimensional area using the traditional method, plane table surveying, planimeter, and then get ground surface area through timing the slope correction factor. In this study, I show the defect and inefficiency of the calculation of the area by the traditional methods and survey the area with Electronic Distance Measuring equipment and GPS instrument. With these data, we made the three dimensional terrain model and calculated two-dimensional area and ground surface area. After that, I compared areas that calculated by algorithm method of irregular triangle and analysis of grid method with standardizing the area that calculated by the traditional method. Finally, I suggested more effective and precise method in calculating ground surface area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.1
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• pp.93-104
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• 1982

DTM data evaluation regards accuracy and efficiency as its most important parameters, and these two elements are sensitively influenced by the sampling technique employed and its procedure. This study attempts to improve sampling techniques and evaluate the accuracy of DTM based on earth volume calculation, using aerial photography and field survey information as basic DTM data, and a regular grid and progressive sampling method for sampling process. Especially, the progressive sampling has employed different combinations of threshold and sampling criteria, that is, parameters influential on efficiency and accuracy, for the purpose of numerical tests intended to permit comparative analysis. The tests have resulted in the findings that in progressive sampling its grid density fits in well with given terrain characteristics in proportion to their variability. and that threshold and accuracy contain close mutual relations in which an increased threshold bringing more efficency but less accuracy. It follows, therefore. that a threshold, when appropriately determined, can be of very efficient use for considerably broad applications, and particularly, will play a significant role in its application to such general civil engineering as earth volume calculation.

• Journal of the Korea Society for Simulation
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• v.32 no.3
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• pp.1-8
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• 2023

Modeling of artificial targets in Synthetic Aperture radar (SAR) mainly simulates radar signals reflected from the faces and edges of the 3D Computer Aided Design (CAD) model with a ray-tracing method, and modeling of the clutter on the Earth's surface uses a method of distinguishing types with similar distribution characteristics through statistical analysis of the SAR image itself. In this paper, man-made targets on the surface and background clutter on the terrain are integrated and made into a three-dimensional (3D) point cloud scatterer model, and SAR image were created through computational signal processing. The results of the SAR Stripmap image generation of the actual automobile based SAR radar system and the results analyzed using EM modeling or statistical distribution models are compared with this 3D point cloud scatterer model. The modeling target is selected as an bridge because it has the characteristic of having both water surface and ground terrain around the bridge and is also a target of great interest in both military and civilian use.

• Journal of IKEEE
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• v.17 no.1
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• pp.1-9
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• 2013

The quantitative evaluation of DEM(Digital Elevation Map) is very important to the assessment of the effectiveness for the applied 3D image analysis technique. This paper presents a new quantitative evaluation method of 3D reconstruction process by using synthetic images. The proposed method is based on the assumption that a preacquired DEM and ortho-image should be the pseudo ground truth. The proposed evaluation process begins by generating a pair of photo-realistic synthetic images of the terrain from any viewpoint in terms of application of the constructed ray tracing algorithm to the pseudo ground truth. By comparing the DEM obtained by a pair of photo-realistic synthetic images with the assumed pseudo ground truth, we can analyze the quantitative error in DEM and evaluate the effectiveness of the applied 3D analysis method. To verify the effectiveness of the proposed evaluation method, we carry out the quantitative and the qualitative experiments. For the quantitative experiment, we prove the accuracy of the photo-realistic synthetic image. Also, the proposed evaluation method is experimented on the 3D reconstruction with regards to the change of the matching window. Based on the fact that the experimental result agrees with the anticipation, we can qualitatively manifest the effectiveness of the proposed evaluation method.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.3
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• pp.164-173
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• 2017

Alternative cropping systems would be one of climate change adaptation options. Suitable areas for a crop could be identified using a climate suitability model. The EcoCrop model has been used to assess climate suitability of crops using monthly climate surfaces, e.g., the digital climate map at high spatial resolution. Still, a high-performance computing approach would be needed for assessment of climate suitability to take into account a complex terrain in Korea, which requires considerably large climate data sets. The objectives of this study were to implement a script for R, which is an open source statistics analysis platform, in order to use the EcoCrop model under a parallel computing environment and to assess climate suitability of maize using digital climate maps at high spatial resolution, e.g., 1 km. The total running time reduced as the number of CPU (Central Processing Unit) core increased although the speedup with increasing number of CPU cores was not linear. For example, the wall clock time for assessing climate suitability index at 1 km spatial resolution reduced by 90% with 16 CPU cores. However, it took about 1.5 time to compute climate suitability index compared with a theoretical time for the given number of CPU. Implementation of climate suitability assessment system based on the MPI (Message Passing Interface) would allow support for the digital climate map at ultra-high spatial resolution, e.g., 30m, which would help site-specific design of cropping system for climate change adaptation.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.4
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• pp.234-246
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• 2007

The role of macropore in the hydrological processes is important at the hillslope scale. Developments and distribution of macropores have not been investigated in conjunction with the characteristics of the hillslope such as topography, soil property, and soil moisture. In this study, macropore properties, such as macropore flow and saturation hydraulic conductivity were measured at a hillslope located in Gwangneung Research Forest, Pochun-gun, Gyeonggi-do, South Korea. An intensive field survey provided a refined Digital Elevation Model (DEM) for surface and subsurface topography. Spatial distributions of upslope area and topographic index were obtained through the digital terrain analysis. The total number of monitoring points was 22, and the selected points were distributed along the transect of the digital contour map. Vertical fluxes through macropores were measured using a tension infiltrometer at the depth of 0.1 m from the surface. Spatial and temporal distributions of soil moisture were obtained using an on-line measurement system, TRASE, installed in the study area. Soil moisture for the aforementioned points was measured at 0.1 and 0.3m depths below the surface. The results from tension infiltrometer experiments present that the macropore flows ranged between 21 and 94%, and the measured macroporosities varied from 1.4 to 47%. Macropore flows and macroporosities tended to increase as the measurement location moved to downslope. The ability for water conduction through macropores becomes increasingly developed as the location approaches the outlet of the hillslope.

• Korean Journal of Remote Sensing
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• v.37 no.6_1
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• pp.1731-1738
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• 2021

The objective of this study was to extract individual trees and tree heights using UAV drone images. The study site was Gongju national university experiment forest, located in Yesan-gun, Chungcheongnam-do. The thinning intensity study sites consisted of 40% thinning, 20% thinning, 10% thinning and control. The image was filmed by using the "Mavic Pro 2" model of DJI company, and the altitude of the photo shoot was set at 80% of the overlay between 180m pictures. In order to prevent image distortion, a ground reference point was installed and the end lap and side lap were set to 80%. Tree heights were extracted using Digital Surface Model (DSM) and Digital Terrain Model (DTM), and individual trees were split and extracted using object-based analysis. As a result of individual tree extraction, thinning 40% stands showed the highest extraction rate of 109.1%, while thinning 20% showed 87.1%, thinning 10% showed 63.5%, and control sites showed 56.0% of accuracy. As a result of tree height extraction, thinning 40% showed 1.43m error compared with field survey data, while thinning 20% showed 1.73 m, thinning 10% showed 1.88 m, and control sites showed the largest error of 2.22 m.

• Journal of the Korean earth science society
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• v.40 no.2
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• pp.119-134
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• 2019

In order to analyze the observational environment of solar radiation stations operated by the Korea Meteorological Administration (KMA), we used the digital elevation model (DEM) and the solar radiation model to calculate a topographical shading, sky view factor (SVF) and solar radiation by surrounding terrain. The sky line and SVF were calculated using high resolution DEM around 25 km of the solar stations. We analyzed the topographic effect by analyzing overlapped solar map with sky line. Particularly, Incheon station has low SVF whereas Cheongsong and Chupungryong station have high SVF. In order to validation the contribution of topographic effect, the solar radiation calculated using GWNU solar radiation model according to the sky line and SVF under the same meteorological conditions. As a result, direct, diffuse and global solar radiation were decreased by 12.0, 5.6, and 4.7% compared to plane surface on Cheongsong station. The 6 stations were decreased amount of mean daily solar radiation to the annual solar radiation. Among 42 stations, eight stations were analyzed as the urgent transfer stations or moving equipment quickly and more than half of stations (24) were required to review the observational environment. Since the DEM data do not include artifacts and vegetation around the station, the stations need a detail survey of observational environment.

• Journal of Convergence for Information Technology
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• v.11 no.1
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• pp.136-142
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• 2021

Open-pit mine development requires continuous management because of topographical changes and there is a risk of accidents if the current status survey is performed directly in the process of calculating the earthwork. In this study, the application of UAV photogrammetry, which can acquire spatial information without direct human access, was applied to open-pit mines development area and analyzed the accuracy, earthwork, and mountain restoration plan to determine its applicability. As a result of accuracy analysis at checkpoint using ortho image and Digital Surface Model(DSM) by UAV photogrammetry, Root Mean Square Error(RMSE) is 0.120 m in horizontal and 0.150 m in vertical coordinates. This satisfied the tolerance range of 1:1,000 digital map. As a result of the comparison of the earthwork, UAV photogrammetry yielded 11.7% more earthwork than the conventional survey method. It is because UAV photogrammetry shows more detailed topography. And result of monitoring mountain restoration showed possible to determine existence of rockfall prevention nets and vegetation. If the terrain changes are monitored by acquiring images periodically, the utility of UAV photogrammetry will be further useful to open-pit mine development.

• Journal of Korea Water Resources Association
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• v.53 no.7
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• pp.545-555
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• 2020

A feasibility modeling for potential hydroelectric dam site selection was suggested using 1 sec ASTGTM (ASTER Global Digital Elevation Model) and Terra/Aqua MODIS (Moderate Resolution Imaging Spectroradiometer) derived land use (MCD12Q1) data. The modeling includes DEM pre-processing of peak, sink, and flat, river network generation, watershed delineation and segmentation, terrain analysis of stream cross section and reservoir storage, and estimation of submerged area for compensation. The modeling algorithms were developed using Python and as an open source GIS. When a user-defined stream point is selected, the model evaluates potential hydroelectric head, reservoir surface area and storage capacity curve, watershed time of concentration from DEM, and compensation area from land use data. The model was tested for 4 locations of already constructed Buhang, BohyunMountain, Sungdeok, and Yeongju dams. The modeling results obtained maximum possible heads of 37.0, 67.0, 73.0, 42.0 m, surface areas of 1.81, 2.4, 2.8, 8.8 ㎢, storages of 35.9, 68.0, 91.3, 168.3×10⁶ ㎥ respectively. BohyunMountain and Sungdeok show validity but in case of Buhang and Yeongju dams have maximum head errors. These errors came from the stream generation error due to ASTGTM. So, wrong dam watershed boundary limit the head. This study showed a possibility to estimate potential hydroelectric dam sites before field investigation especially for overseas project.