• Title/Summary/Keyword: Elevation Model

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Evolution of Internal Waves Near a Turning Point in the South China Sea using SAR Imagery and Numerical Models

  • Kim, Duk-Jin;Lyzenga, David R.;Choi, Woo-Young;Kim, Youn-Soo
    • Korean Journal of Remote Sensing
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    • v.23 no.5
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    • pp.385-391
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    • 2007
  • Subsurface Internal Waves(IWs) can be detected in satellite images as periodic alternating brighter/darker stripes. It is known that there are two types of IWs-depression type and elevation type-depending on the water depth in stratified oceans. In this study, we have quantitatively verified the process of converting polarity from depression waves to elevation waves using ERS-2 SAR image acquired over the northern South China Sea. We simulated the evolution of IWs near a turning point with a numerical model for internal wave propagation. The simulation results near the turning point clearly showed us not only a conversion process of IWs from depression to elevation waves, but also a similar wave pattern with the observed SAR image. We also simulated SAR intensity variation near the turning point. The upper layer currents were computed at regular intervals using the numerical model, as the IWs were passing through the turning point. Then, an integrated hydrodynamic-electromagnetic model was used for simulating SAR intensity profiles from the upper layer currents. The simulated SAR intensity profiles were compared with the observed SAR intensities.

FINITE ELEMENT MODELING FOR HYDRODYNAMIC AND SEDIMENT TRANSPORT ANALYSIS (II) : SEDIMENT TRANSPORT STUDY

  • Noh, Joon-Woon
    • Water Engineering Research
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    • v.4 no.2
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    • pp.99-109
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    • 2003
  • Since bed elevation changes are mainly dependent on the flow velocity and corresponding shear stress, it is possible to predict bed elevation numerically using velocity components. For the scour analysis due to channel contraction, a bed load transport model is developed and applied to estimate scour depth around coffer dam in the Mississippi River. During Phase I of the Lock & Dam No. 26 replacement project, a coffer dam was constructed to reduce the flow area approximately by 50%. Flow velocity increases due to the flow area reduction yields significant lowering (erosion) of the channel bed elevation. The proposed numerical model solves the sediment continuity equation using the finite element method to evaluate scour process in the vicinity of the coffer dam

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Analysis of Flood Inundation Area using HEC-RAS/GIS (HEC-RAS/GIS를 이용한 홍수 범람지역 분석)

  • An, Seung Seop;Lee, Jeung Seok;Kim, Jong Ho
    • Journal of Environmental Science International
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    • v.13 no.1
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    • pp.19-26
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    • 2004
  • The purpose of the study was to construct a forecast system of flood inundation area at natural stream channels. The study built the system to interpret the flood inundation area in four stages ; constructing topography data around the stream channel, interpreting flood discharge, interpreting flood elevation in the stream channel, and interpreting the flood inundation and mapping. According to the result of the analysis, as for the characteristic of flood inundation around the area within the purview of this study, although there were areas where flood inundation over a bank caused a flooded area, the failure of the internal drainage in the ground lower than flood elevation caused more serious problems. Rather than the existing method where only the estimated flood elevation data is used based on the hydrographical stream channel trace model(such as the HEC-RAS model) to establish the flood inundation area, if the procedure introduced in this study was applied to interpret the floodplain, actual flood inundation area could be visibly confirmed.

Automatic Generation of a SPOT DEM: Towards Coastal Disaster Monitoring

  • Kim, Seung-Bum;Kang, Suk-Kuh
    • Korean Journal of Remote Sensing
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    • v.17 no.2
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    • pp.121-129
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    • 2001
  • A DEM(digital elevation model) is generated from a SPOT panchromatic stereo-pair using automated algorithms over a 8 km$\times$10 km region around Mokpo city. The aims are to continue the accuracy assessment over diverse conditions and to examine the applicability of a SPOT DEM for coastal disaster monitoring. The accuracy is assessed with respect to three reference data sets: 10 global positioning system records, 19 leveling data, and 1:50,000 topography map. The planimetric error is 10.6m r.m.s. and the elevation erroer ranges from 12.4m to 14.4m r.m.s.. The DEM accuracy of the flat Mokpo region is consistent with that over a mountainous area, which supports the robustness of the algorithms. It was found that coordinate transformation errors are significant at a few meters when using the data from leveling and topographic maps. The error budget is greater than the requirements for coastal disaster monitoring. Exploiting that a sub-scene is used, the affine transformation improves the accuracy by 50% during the camera modeling.

GENERATION OF DEM FROM CONTOURS FOR THE ORTHORECTIFICATION OF HIGH-RESOLUTION STELLITE IMAGES

  • Choi, Joon-Soo;Cha, Young-Min;Heo, Jae-Wee;Ryu, Young-Soo;Kim, Choen;Oh, Seung-Jun
    • Proceedings of the KSRS Conference
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    • 2008.10a
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    • pp.7-10
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    • 2008
  • We present a technique for constructing a digital elevation model (DEM) from contours. The elevation of each ground point in DEM is computed by interpolating the heights of the two adjacent contours of the point. The technique decomposes each sub-domain between adjacent contours into a set of sub-regions. The decomposition is accomplished by constructing a medial axis of the sub-domain. Each sub-region in the decomposition is classified into a variety of terrain features like hillsides, valleys, ridges, etc. The elevations of points are interpolated with different methods according to terrain features they belong to. For a given point in hillside, an approximate gradient line passing through the point is determined and the elevation of the point is interpolated from the known elevations of the two adjacent contours along the approximate gradient line. The univariate monotone rational Hermite spline is used for the interpolation. The DEM constructed by the technique is to be used to orthorectify the high-resolution KOMPSAT3 imagery.

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The Structural Relationship between the Possibility of Socioeconomic Class Elevation of Workers and Related Variables

  • Hyo-Young LEE
    • The Journal of Industrial Distribution & Business
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    • v.14 no.10
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    • pp.35-43
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    • 2023
  • Purpose: The purpose of this study is to analyze the structural relationship between the possibility of socioeconomic class elevation of wage earners, happiness and organizational commitment, and life satisfaction. Research design, data and methodology: Data from the 24th fiscal year (2021) of the Korea Labor Panel data were used for analysis. Only wage earners who measured job satisfaction and organizational engagement were analyzed, and a sample of 9,138 respondents was finally used, excluding missing values. Structural Equation Modeling was performed using AMOS 23.0, and Maximum Likelihood Estimation (MLE) was used as a model estimation method. Results: First, the hypothetical structural model set up for the study was found to be suitable. Second, the Possibility of Socioeconomic Class Elevation of wage earners, happiness, and organizational commitment were found to have a direct impact on life satisfaction. Third, the possibility of improving the socio-economic status of wage earners affects life satisfaction, and happiness and organizational commitment appear to have a partially mediating effect. Conclusions: This study is significant in that it has increased interest in organizational participation and life satisfaction, which were not covered in previous studies on the possibility of wage workers moving up the socioeconomic class.

A Study on the Data Driven Neural Network Model for the Prediction of Time Series Data: Application of Water Surface Elevation Forecasting in Hangang River Bridge (시계열 자료의 예측을 위한 자료 기반 신경망 모델에 관한 연구: 한강대교 수위예측 적용)

  • Yoo, Hyungju;Lee, Seung Oh;Choi, Seohye;Park, Moonhyung
    • Journal of Korean Society of Disaster and Security
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    • v.12 no.2
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    • pp.73-82
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    • 2019
  • Recently, as the occurrence frequency of sudden floods due to climate change increased, the flood damage on riverside social infrastructures was extended so that there has been a threat of overflow. Therefore, a rapid prediction of potential flooding in riverside social infrastructure is necessary for administrators. However, most current flood forecasting models including hydraulic model have limitations which are the high accuracy of numerical results but longer simulation time. To alleviate such limitation, data driven models using artificial neural network have been widely used. However, there is a limitation that the existing models can not consider the time-series parameters. In this study the water surface elevation of the Hangang River bridge was predicted using the NARX model considering the time-series parameter. And the results of the ANN and RNN models are compared with the NARX model to determine the suitability of NARX model. Using the 10-year hydrological data from 2009 to 2018, 70% of the hydrological data were used for learning and 15% was used for testing and evaluation respectively. As a result of predicting the water surface elevation after 3 hours from the Hangang River bridge in 2018, the ANN, RNN and NARX models for RMSE were 0.20 m, 0.11 m, and 0.09 m, respectively, and 0.12 m, 0.06 m, and 0.05 m for MAE, and 1.56 m, 0.55 m and 0.10 m for peak errors respectively. By analyzing the error of the prediction results considering the time-series parameters, the NARX model is most suitable for predicting water surface elevation. This is because the NARX model can learn the trend of the time series data and also can derive the accurate prediction value even in the high water surface elevation prediction by using the hyperbolic tangent and Rectified Linear Unit function as an activation function. However, the NARX model has a limit to generate a vanishing gradient as the sequence length becomes longer. In the future, the accuracy of the water surface elevation prediction will be examined by using the LSTM model.

The Effect of Grid Size in a Slope Analysis of Terrain by DEM for Hydrological Analysis (수문해석을 위한 DEM에 의한 지형의 경사도분석에서 격자크기의 영향)

  • 양인태;김연준
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.15 no.2
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    • pp.221-230
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    • 1997
  • In hydrology analysis, the result of a slope analysis for terrain have an very important effect on water quality and water quantity Recently, a slope analysis tend to use the digital elevation model rater than the traditional map sheet. But a terrain slope analysis by the digital elevation model depends on grid size of the digital elevation model. Hence the effect of a slope analysis by the digital elevation model is a important factor. In this study, therefor, in order to determine a hydrological parameter and a terrain parameter for simulation of the water quality and the hydrological property, we adapted two sample area that are the Nerin stream of the basin of the Soyang lake and a Osip stream of Samchuk, and its individual coverages are $640\;km^2$ and $33\;km^2$. Also to analyze the effect of grid size in the slope of a basin, we apply DEM changing a grid size respectively at intervals of 100 m from 100 m to 1.000m for the Nerin stream basin and at intervals of 10 m from 20 m to 300 m for the Osip stream basin.

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Image Resampling for Epipolar Geometry in Digital Photogrammetry (數値寫眞測量에 있어서 epipolar 幾何狀態를 形成하기 위한 映像再配列)

  • Yeu, Bock-Mo;Youn, Kyung-Chul;Jeong, Soo
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.10 no.2
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    • pp.25-30
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    • 1992
  • Most algorithms in computer vision and digital photogrammetry assume that digital stereo pairs are registered in epipolar geometry. But, an aerial stereo pair is not likely to be in epiplar geometry since the attitude of the camera at the instant of exposure is different at every exposure station. In this paper, stereo digital imagery is obtained from aerial stereo pair by scanner. Then procesure to resample the digital imagery to epipolar geometry using exterior orientation elements after absolute orientation is described. As a result, a stereo imagery in epipolar geometry is produced from stereo digital imagery. Epipolar imagery in this paper is applied to the image matching method by digital image correlation technique. Then, a digital elevation model is produced from the result of image matching. The digital elevation model in this paper is compared to the other digital elevation model produced by analytical plotter. As a result, an economical method to generate digital elevation model is presented.

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A Study to Determine the Slope Length and Steepness Factor of Universal Soil Loss Equation with Determining and Adapting Major Slope Length at Field Scale (필지 단위 주경사장 산정 및 적용을 통한 범용토양유실공식 지형인자 산정 개선 연구)

  • Park, Youn Shik;Park, Jong-Yoon;Jang, Won Seok;Kim, Jonggun
    • Journal of The Korean Society of Agricultural Engineers
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    • v.61 no.6
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    • pp.55-65
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    • 2019
  • Universal Soil Loss Equation (USLE) is to estimate potential soil loss and has benefit in use with its simplicity. The equation is composed of five factors, one of the factors is the slope length and steepness factor (LS factor) that is for topographic property of fields to estimate potential soil loss. Since the USLE was developed, many equations to compute LS was suggested with field measurement. Nowadays the factor is often computed in GIS software with digital elevation model, however it was reported that the factor is very sensitive to the resolution of digital elevation model. In addition, the digital elevation model of high resolution less than 3 meter is required in small field application, however these inputs are not associate with the empirical models' backgrounds since the empirical models were derived in 22.1 meter field measurements. In the study, four equation to compute LS factor and two approaches to determine slope length and steepness were examined, and correction factor was suggested to provide reasonable precision in LS estimations. The correction factor is computed with field area and cell size of digital elevation model, thus the correction factor can be adapted in any USLE-based models using LS factor at field level.