• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.3
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• pp.290-297
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• 1994

As satellite altimetry is being progressed to apply with higher precision to marginal seas, it is necessary to improve correction procedures fer tidal signals in altimetry with more accurate tidal model than the well-known model of Schwiderski. The Bay of Bengal renders many conspicuous coastal oceanographic issues including tide and storm surge interactions along the upper Bangladesh coast. As a first step. tidal regime of semidiurmal tides (M$_2$, S$_2$, $N_2$, $K_2$) and diurnal tides (K$_1$, $O_1$, P$_1$) are computed with a model having a mesh resolution of 1/4 degree over the whole Bay of Bengal. Computed results are discussed with observation and previous Schwideski's tidal map of the region.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2003.04a
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• pp.115-120
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• 2003

일반적으로 광학위성은 궤도가 부정확하여 지상기준점(GCP)을 이용하여 궤도를 보정하는 작업을 수행한 후 수치 표고모형 자료(DEM)를 추출한다. 지상기준점은 실제 측량이나 지형도로부터 얻게 되지만, 이러한 작업이 불가능한 경우에는 광학영상으로부터 수치 표고 모형 자료를 추출할 수 없다. 본 연구에서는 수-수십 cm의 위성 궤도 정확도를 지니는 ESA ERS영상과 약 1Km의 해상도를 지니는 GTOPO-30 DEM을 이용하여 지상기준점을 추출 방법에 대해 연구하였다. 연구지역인 대전 주변에 대하여 지상기준점을 추출한 결과 경도 -0.348초, 위도 0.293초의 오차를 나타내었다. 또한 추출된 지상기준점을 이용하여 한 쌍의 SPOT 위성영상으로부터 DEM을 추출이 가능하였으며, 레이더 interferometry 기술을 이용한 지형고도 추출 및 변화 탐지에도 활용될 수 있음을 확인하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.144-146
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• 2019

과거의 해안선조사방법으로는 GNSS가 도입되면서 크게 발전하여 위성측위기를 이용한 현장조사방법과 항공기를 이용한 사진측량 방법이 조사의 주를 이루었다. 그러나, 현재 무인항공기(UAV)를 이용한 저고도 정밀조사 방법이 도입되어 무인항공기를 이용한 정밀사진측량이 가능하게 되었다. 무인항공기 정밀사진측량은 기존 조사방법과 비교시 저비용, 고정밀 성과를 취득 할 수 있다. 무인항공기 정밀사진측량은 해안선변화조사에 적용되어 무인항공기 정밀사진측량에서 취득된 고정밀 정사영상 및 수치표면모형(DSM)자료를 이용해 해안선을 추출하고 해안선변화 지역을 분석하는 자료로 활용되고 있다. 2016년도부터 우리나라 해안선변화조사 사업에 무인항공기를 이용한 조사가 실시되고 있으며 추후 여러 다방면으로 무인항공기를 이용한 다양한 조사가 이루어 질것으로 기대 된다.

• Journal of Korea Spatial Information System Society
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• v.3 no.2 s.6
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• pp.5-19
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• 2001

We are able to construct and utilize DEM(Digital Elevation Model) throughout the NGIS(National Geographic Information System) project. It is important that interpolation methods and appreciate size of grid for the construction of accurate DEM(Digital Elevation Model). There were several references related to the DEM(Digital Elevation Model) construction method, however they couldn't consider various topographical characteristics in the korea. In this study, we recommended that suitable interpolation method for each topographic element. After dividing Poonggi area into mountain, hill, urban, agricultural land, we constructed DEM(Digital Elevation Model) with various interpolation methods and grid size using 1:5,000 digital map. Then evaluated accuracy using elevation data which extracted from air-photo. The interpolation methods were analyzed and compared for various topographical conditions. As a result, Kriging method was superior to TIN method for all the topographical conditions. Another experiment was performed to examine optimal grid space for DEM with each topographical condition. 10m grid space was most suitable for mountain area and hilly districts, while 30m grid space was most suitable for urban area and farm land.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.496-499
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• 2004

컴퓨터와 다양한 software의 보급과 함께 흐름의 수치해석 분야는 급속한 발전을 보게 되었고 고도의 수치해법이나 복잡한 경계 처리 등을 통해 실제현상과 같은 흐름해석을 가능케 하고 있으며, 이러한 수치해석을 위해 정확한 Bathymetry는 필수적이다. 본 연구에서는 등 격자간격의 수심도 생성을 위하여 전자해도를 작업에 적합하게 수정하고 부족한 조간대의 수심자료는 보완하고, 파일형식에 따른 적절한 프로그램밍 언어를 통하여 해도상 지점들의 수심자료를 획득하고 내삽하여 기존에 사용되는 방법에 비하여 비교적 간단하고 해도의 정보를 정확하게 반영하는 Bathymetry를 생성하는 기법을 제안하였다.

• Journal of the Korean Geographical Society
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• v.34 no.3
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• pp.319-336
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• 1999

본 연구는 우리나라의 수치지형도에서 수치고도모형(DEM)을 개발하고자 할 때 고려해야 할 요인들을 분석하였다. 특히 DEM의 정확도에 결정적으로 영향을 미치는 내삽법의 과정을 지형적 유형(평지.계곡.산지)과 공간적 표본추출법(체계적추출법.군집형무작위추출법.복합점진적표본추출법)에 따라 구분하여 살펴 보았다. RMSE의 측정을 통해 크리깅 내삽법이 지형의 기복에 산관없이 정확도를 유지함녀서 DEM을 생성할 수 있는 방법으로 평가되었다. 그리고 표본추출법에 따라 공간적 표본 밀도를 달리한 낮은 표본을 대상으로 한 경우에 비해 낮게 나타났다. 또한 본 연구에서 제안한 복합 점진적 표본추출법을 적용한 DEM의 정확도는 다른 표본추출법을 적용한 경우보다 그 정확도가 향상됨을 확인하였고, 반면에 계산상의 효율성이 다른 방법에 비해 떨어지는 단점을 보였다.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.279-288
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• 2000

The impact of land slope to the degree of flow divergence was considered employing distributional applications of slope exponents in the now directlOn algoriUnns. Lmear, exponential and ]X)wer law of distributional functIons were employed to address the variation of slope exponents m a terrain analysis. Dongok subwatershed at Wichun test watershed was selected as a study area. Digital Elevation Models of 20m, 30m, 40m and 50m grid size were made to perfonn the analysis. Various calcualtion methodologies of topographic index and the impact of grid sizes were investigated in terms of statistical and spatial aspects. DIstributional applications of slope e.xponents made it possible to represent the flow divergence and convergence about the ten-ain characteristics. The Monte~Carlo method was used to simulate six runoff events to check the impact of topographic factor in the runoff simulation.

• 한국공간정보시스템학회:학술대회논문집
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• 2000.06a
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• pp.67-76
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• 2000

Recently, SAR Interferometry method is actively being studied as a new technic in topographic mapping using satellite imageries. it extract height values using two SAR imageries covering same areas. Unlike when using SPOT imageries, it isn't affected by atmospheric conditions and time. But it is difficult to process radar imageries and the height accuracy is very low where relief displacements are high. In this study, we produced DEM(Digital Elevation Model) using ERS-1, ERS-2 tandem data and analysed the height accuracy over 14 ground control points. The mean error in height was 14.06m. But when using airborne SAR data, it Is expected that we can produce more accurate DEM which will be able to ue used in updating 1/10,000 or 1/25,000 map.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.15 no.1
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• pp.51-61
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• 1997

A two-dimensional numerical tidal model with $1/3^\circ$ resolution has been established to investigate the distribution of semidiurnal constituents$(M_2,\;S_2,\;K_2,\;N_2)$ and diurnal constituents$(K_1,\;O_1,\;P_1,\;Q_1)$ of the global ocean. The $1/3^\circ$ numerical model has been applied to the computation of detailed tidal distributions in the marginal seas and the shelf seas. Tidal characteristics in shallow areas could be hardly resolved with the existing global chart due to the low resolution. Computed tidal charts obtained by $1/3^\circ$ numerical model have been compared with the existing global charts and the altimetry-derived tidal charts. Computed harmonic constants have also been com-pared with the pelagic tidal observations. The results obtained with fine-grid numerical model can be used to determine the time-independent sea surface topography by removing the tidal components from the altimetry-derived sea surface height.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.115-123
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• 2005

Quantitative understanding of spatial characteristics of the study site is a prerequisite to investigate water and carbon cycles in agricultural and forest ecosystems, particularly with complex, heterogeneous landscapes. The spatial characteristics of variables related with topography, vegetation and soil in Gwangneung forest watershed are quantified in this study. To characterize topography, information on elevation, slope and aspect extracted from DEM is analyzed. For vegetation and soil, a land-cover map classified from LANDSAT TM images is used. Four satellite images are selected to represent different seasons (30 June 1999, 4 September 2000, 23 September 2001 and 14 February 2002). As a flux index for CO₂ and water vapor, normalized difference vegetation index (NDVI) is calculated from satellite images for three different grid sizes: MODIS grid (7km x 7km), intensive observation grid (3km x 3km), and unit grid (1km x 1km). Then, these data are analyzed to quantify the spatial scale of heterogeneity based on semivariogram analysis. As expected, the scale of heterogeneity decreases as the grid size decreases and are sensitive to seasonal changes in vegetation. For the two unit grids where the two 40 m flux towers are located, the spatial scale of heterogeneity ranges from 200 to 1,000m, which correspond well to the climatology of the computed tower flux footprint.