• Journal of Wetlands Research
• /
• v.12 no.1
• /
• pp.63-73
• /
• 2010

Rainfall is one of the most important input data of hydrologic models. Rain gage is used to estimate areal rainfall for hydrologic models using several interpolation method such as Thiessen polygon, Inverse Distance Squared(IDS) and Kriging. However, it is still difficult to derive actual spatial distribution of the rainfall using the aforementioned approaches. On the other hand, radar can offer a significant analytic improvement for rainfall analysis by providing directly more representative of the true spatial distribution of rainfall. In this study, In this study, spatial distributions of rainfall derived form rain gages using IDS and Kriging and rainfall from radar are compared. As results, it is found that using radar can provide actual spatial distribution than rain gages.

• Journal of Korea Water Resources Association
• /
• v.51 no.5
• /
• pp.451-459
• /
• 2018

We calculated the optimal exponent values based on the hourly rainfall data observed in South Korea by treating the exponent value as a variable without fixing it as a square in the inverse distance method. For this purpose, rainfall observation stations providing the data are classified into four groups which are located at the Han river upstream, downstream, the Geum river upstream, and the Nakdong river midstream area. A total of 52 cases were analyzed for seven stations in each group. The optimal exponent value of distance was calculated in a case including one base station and four surrounding stations in a group. We applied the golden section search method to calculating this optimum values using rainfall data for 10 years (2004~2013) and verified the optimum values for the last three years (2014~2016). We compared and analyzed two results of the conventional inverse distance method and the inverse distance method in this study. The optimal values of distance exponent obtained in this study were 3.280, 1.839, 2.181, and 2.005 respectively, in the four groups, and totally mean value was 2.326. It is shown the proposed inverse distance method applying the optimal exponent is superior to the conventional inverse distance method.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.247-247
• /
• 2018

공학이나 과학에서 다루는 거의 모든 현상이나 물체는 시공간적으로 연속성을 지니고 있으며, 지형이나 지하수위분포가 대표적인 사례에 해당한다. 강수량 분포 또한 지역적인 스케일을 고려할 때 연속성을 지니고 있다고 가정될 수 있다. 이러한 연속성을 지닌 현상이나 물체를 연구 대상으로 취할 경우, 모든 위치에서의 관찰 값이나 계산 값을 얻기란 불가능하므로, 불연속적이거나 이산적인 위치에서 불연속적인 값을 얻게 된다. 이러한 시공간적으로 이산적이고 불연속적인 자료를 바탕으로 어떠한 작업을 수행하고자 할 때 자료의 연속성을 가정하게 되며, 따라서 연속성을 가정하고 내삽 처리된 근사값을 이용하게 된다. 따라서 불연속적인 자료의 내삽 처리 과정이 연구 결과의 성패를 좌우할 만큼 매우 중요할 수 있다. 하지만 대다수의 연구자나 실무자들은 내삽 처리의 중요성을 간과하고 있으며, 자료처리나 준비 과정에서 거쳐야하는 하나의 단순한 단계로만 여길 뿐이다. 따라서, 본 연구에서는 역거리 가중치법(Reciplocal Inverse Distance method), 역거리 제곱 가중치법(Inverse Square Distance method), Dual Kriging법, Hardy의 Multiquadric법, Completely Regularized spline법, 삼각망법(TIN) 등 기존에 알려진 공간자료 보간법에 대해서 소개하며, 알려져 있는 공간함수를 이용하여 다양한 경우에 대한 비교, 분석을 수행한다. 보간법의 종류에 따라 내삽 결과는 매개변수 값에 지대한 영향을 받을 수 있기 때문에, 매개변수에 따른 내삽 결과를 분석하고, 정확성과 적용성 등 다양한 내삽기법들에 대해서 평가한다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.701-705
• /
• 2006

강우자료는 수문 모델링 작업에서 가장 기초적인 수문학적 입력자료로 시간과 공간에 따른 변동성이 크므로 규명하기 복잡한 수문현상 중의 하나이다. 산악지역이 많은 우리나라의 지형학적 특성과 태풍, 장마 및 특히, 최근의 게릴라성 집중호우 등으로 인하여 이러한 변동성이 더욱 커지고 있는 실정이다. 장기간 실측된 수문기상 기초 자료가 부족한 우리나라의 실정상 홍수예보 및 수공구조물 설계를 위해 정확한 강우량 자료의 취득이 선행돼야 한다. 따라서 적절한 장소에 수문관측소 설치 및 관리를 통해 양호한 강우량 자료를 획득해야 하지만, 현장 여건상 등의 이유로 미계측 및 결측, 이상자료가 발생하고 있다. 따라서 이러한 미계측 혹은 결측지점의 우량을 추정할 수 있는 방법을 비교, 분석하여 적절한 보정과정을 수행할 필요가 있다. 그간의 연구에서는 미계측 지점 혹은 산악지역에서의 점 강우량 보정방법에 대한 연구가 진행되었지만, 본 연구에서는 '도시홍수재해관리기술연구사업단'에서 운영 중인 도시하천 유역 특히 소배수구역에서의 결측 자료에 대해 여러 추정 방법을 비교, 분석하여 적절한 방안을 찾고자 한다. 이를 위하여 중랑천 유역의 3개 소배수 구역(월계1 배수구역, 군자 배수구역, 어린이대공원 배수구역)에 설치된 3개 우량관측소와 건설교통부 관할 우량관측소 2개소의 우량자료를 사용하였다. 본 연구에서는 결측치 보간을 위하여 널리 이용되고 있는 산술평균법(Arithmetic Average method), 역거리법(Reciprocal Distance Squared method), 거리고도비율법(Ratio of Distance and Elevation method), 인근관측소와의 관계식 이용, 크리깅방법(Simple Kriging method)을 비교, 검토 적용하였다. 중랑천 유역의 소배수구역을 대상으로 연중 발생하는 큰 호우사상에 대해 임의의 강우관측소를 결측지점으로 가정하고 주변의 강우관측소로부터 각각의 방법을 이용해 가중치들을 산정하여 결측지점의 강우량 값을 보정하고자 하였다. 또한 각각의 방법을 이용하여 얻어진 결과에 대해 실측값과 보정값의 오차정도를 평균절대오차법(Mean Absolute Error)과 제곱평균제곱근오차법(Root Mean Squared Error)에 의해 산정하여 보정 방법간의 효율성을 검토하고자 하였다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5A
• /
• pp.917-925
• /
• 2006

Experimental tests were performed to estimate velocities of the acoustic signals through prestressed concrete beam and source locations using acoustic emission (AE) techniques. Seven AE sensors are mounted on the surface of 5m length test beam with equal spacing and using Schmidt Hammer AE events are made at 18 locations. The velocities of AE signals are estimated using the time differences of arrival times and the distances between the source locations and the AE sensor locations. In addition, using the Least Square Method, the AE source locations are re-evaluated reversely using both of the arrival times and the velocities of AE signals. Test results show the average velocity of the AE signals is about 4,000 m/sec and the velocity decreased with the increase of the distance from source locations to AE sensors due to the effect of attenuation. Based on the estimation of the source locations, it is observed that the errors of source locations are decreased when the velocities of each AE sensor are used rather than the average velocity.

• Journal of Korea Water Resources Association
• /
• v.48 no.5
• /
• pp.357-365
• /
• 2015

Both exponents of distance and elevation into distance-and-elevation ratio method for estimating missing rainfall data are expressed as squares together but in this study the two exponents are differently separated and analyzed. We used 326 hourly rainfall events of precipitation data during 10 years of 2004 to 2013 observed at a base station of Pyeongchang and the five neighboring index stations-Bangrim, Suju, Cheongoksan, Jinbu, Yeongwol1-in Han River basin for a case study. As a result, exponent values of distance and elevation appropriate for a topography of the site appear as 3.7 and 0.57 respectively. The exponents of distance and elevation difference need to be applied according to topographical characteristics of site where estimating missing data or interpolation are required.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.7
• /
• pp.33-44
• /
• 2004

This paper is focused on the spatial variability of measured strong motion data during earthquake and its relationship with the performance of water distribution pipelines and residential buildings. Analyses of strong motion and the correlations of peak ground velocity (PGV) and pipeline and building damage were conducted with a very large geographical information system (GIS) database including the relationship of time and earthquake intensity and the measured location, and Kriging spatial statistics. Kriging was used to develop regressions of pipeline repair rate (RR) and residential building damage ratio (DR) associated with $90\%$ confidence peak ground velocity (PGV). Such regressions using Kriging provide an explicit means of characterizing the uncertainty embodied in the strong motion data compared with other spacial statistics such as inverse distance method.

• Korean Journal of Remote Sensing
• /
• v.19 no.6
• /
• pp.431-445
• /
• 2003

In this paper, we experimentally investigated the precision of 3D positioning using 4S-Van images in photograrmmetric perspective. The 3D calibration target was built over building facade outside and was captured separately by two CCD cameras installed in 4S-Van. After then, we determined the interior orientation parameter for each CCD camera through self-calibration technique. With the interior orientation parameter computed, the bundle adjustment was performed to obtain the exterior orientation parameters simultaneously for two CCD cameras using calibration target image and object coordinates. The reverse lens distortion coefficients were computed and acquired by least squares method so as to introduce lens distortion into epipolar line. It was shown that the reverse lens distortion coefficients could transform image coordinates into lens distorted image coordinates within about 0.5 pixel. The proposed semi-automatic matching scheme incorporated with lens distorted epipolar line was implemented with scene images captured by 4S-Van in moving. The experimental results showed that the precision of 3D positioning from 4S-Van images in photograrmmetric perspective is within 2cm in the range of 20m from the camera.

• Journal of KIISE:Software and Applications
• /
• v.32 no.7
• /
• pp.612-624
• /
• 2005

In this paper, we propose a surface-based registration using a gaussian weighted distance map for PET-CT brain image fusion. Our method is composed of three main steps: the extraction of feature points, the generation of gaussian weighted distance map, and the measure of similarities based on weight. First, we segment head using the inverse region growing and remove noise segmented with head using region growing-based labeling in PET and CT images, respectively. And then, we extract the feature points of the head using sharpening filter. Second, a gaussian weighted distance map is generated from the feature points in CT images. Thus it leads feature points to robustly converge on the optimal location in a large geometrical displacement. Third, weight-based cross-correlation searches for the optimal location using a gaussian weighted distance map of CT images corresponding to the feature points extracted from PET images. In our experiment, we generate software phantom dataset for evaluating accuracy and robustness of our method, and use clinical dataset for computation time and visual inspection. The accuracy test is performed by evaluating root-mean-square-error using arbitrary transformed software phantom dataset. The robustness test is evaluated whether weight-based cross-correlation achieves maximum at optimal location in software phantom dataset with a large geometrical displacement and noise. Experimental results showed that our method gives more accuracy and robust convergence than the conventional surface-based registration.

• Journal of Wetlands Research
• /
• v.21 no.spc
• /
• pp.51-60
• /
• 2019

In this study, we performed At-site Frequency Analysis(AFA) and Regional Frequency Analysis(RFA) using the observed and climate change scenario data, and the relative root mean squared error(RMMSE) was compared and analyzed for both approaches through Monte Carlo simulation. To evaluate the rainfall quantile, the daily rainfall data were extracted for 615 points in Korea from HadGEM3-RA(12.5km) climate model data, one of the RCM(Regional Climate Model) data provided by the Korea Meteorological Administration(KMA). Quantile mapping(QM) and inverse distance squared methods(IDSM) were applied for bias correction and spatial disaggregation. As a result, it is shown that the RFA estimates more accurate rainfall quantile than AFA, and it is expected that the RFA could be reasonable when estimating the rainfall quantile based on climate change scenarios.