• Smart Structures and Systems
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• 제21권5호
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• pp.601-609
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• 2018

The estimated probabilistic model of wind data based on the conventional approach may have high discrepancy compared with the true distribution because of the uncertainty caused by the instrument error and limited monitoring data. A sequential quadratic programming (SQP) algorithm-based finite mixture modeling method has been developed in the companion paper and is conducted to formulate the joint probability density function (PDF) of wind speed and direction using the wind monitoring data of the investigated bridge. The established bivariate model of wind speed and direction only represents the features of available wind monitoring data. To characterize the stochastic properties of the wind parameters with the subsequent wind monitoring data, in this study, Bayesian inference approach considering the uncertainty is proposed to update the wind parameters in the bivariate probabilistic model. The slice sampling algorithm of Markov chain Monte Carlo (MCMC) method is applied to establish the multi-dimensional and complex posterior distribution which is analytically intractable. The numerical simulation examples for univariate and bivariate models are carried out to verify the effectiveness of the proposed method. In addition, the proposed Bayesian inference approach is used to update and optimize the parameters in the bivariate model using the wind monitoring data from the investigated bridge. The results indicate that the proposed Bayesian inference approach is feasible and can be employed to predict the bivariate distribution of wind speed and direction with limited monitoring data.

• 한국측량학회지
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• 제40권4호
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• pp.325-332
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• 2022

우주 측지 기술 사이의 상대적인 위치 관계를 설명하는 벡터를 결정하기 위해서는 VLBI IVP (Very Long Baseline Interferometry Invariant Point)의 위치를 정밀하게 계산하여야 한다. 이를 위해 일반적으로 VLBI 안테나에 반사 타겟을 부착한 후 필라들로부터 경사 거리, 수평각, 수직각을 관측한다. 그 다음 단계에서는 관측값과 미지수를 연결하는 수학 모델을 이용하여 조정 계산을 수행하게 된다. 따라서 계산된 미지수는 관측값의 정밀도에 영향을 받게 된다. 이때 특히 문제가 되는 것은 반사 타켓이 일반적인 측량 정밀도를 확보하기 어려운 곳에 위치하고 있다는 점이다. 즉, 반사 타겟의 방향을 조정하여 측량 기기에 정확하게 맞출 수 없다는 것이다. 따라서 이러한 부분은 관측 오차에 또 다른 형태로 나타날 것이며 조정 계산 시 오차 모델링에 오류를 발생시킬 수도 있다. 본 연구에서는 조정 계산 후 계산된 잔차의 특성에 대한 분석을 수행하였다. 먼저 관측 타입별 통계 분석을 통해 정규성을 검정하였으며 분산에 차이가 있는 지에 대한 검정도 실시하였다. 관측 타입별로 등분산 검정을 한 경우 분산이 서로 다른 것으로 나타났다. 각 필라에 대해 관측 타입별 등분산 검정을 했을 때 경사 거리와 수평 및 수직각 사이에는 분산에 차이가 있는 것으로 나타났다. 따라서 결합 측량으로부터 최적의 결과를 얻기 위해서는 관측 오차에 대해 보다 세분화된 모델링이 필요한 것으로 나타났다.

• Korean Journal of Geomatics
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• 제1권1호
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• pp.1-5
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• 2001

This paper presents an investigation into the operational comparison of SPOT triangulation to build GCP library by analytical plotter and DPW (digital photogrammetric workstation). GCP database derived from current SPOT images can be used to other image sensors of satellite, if any reasons, such as lack of topographic maps or GCPs. But, general formulation of a photogrammetric process for GCP measurement has to take care of the scene interpretation problem. There are two classical methods depending on whether an analytical plotter or DPW is being used. Regardless of the method used, the measurement of GCPs is the weakest point in the automation of photogrammetric orientation procedures. To make an operational comparison, five models of SPOT panchromatic images (level 1A) and negative films (level 1AP) were used. Ten images and film products were used for the five GRS areas. Photogrammetric measurements were carried out in a manual mode on P2 analytical plotter and LH Systems DPW770. We presented an approach for exterior orientation of SPOT images, which was based on the use of approximately eighty national geodetic control points as GCPs which located on the summit of the mountain. Using sixteen well-spaced geodetic control points per model, all segments consistently showed RMS error just below the pixel at the check points in analytical instrument. In the case of DPW, half of the ground controls could not found or distinguished exactly when we displayed the image on the computer monitor. Experiment results showed that the RMS errors with DPW test was fluctuated case by case. And the magnitudes of the errors were reached more than three pixels due to the lack of image interpretation capability. It showed that the geodetic control points is not suitable as the ground control points in DPW for modeling the SPOT image.

• 대기
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• 제32권1호
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• pp.27-37
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• 2022

The Korean Integrated Model (KIM) forecast system was extended to assimilate Horizontal Line-Of-Sight (HLOS) wind observations from the Atmospheric Laser Doppler Instrument (ALADIN) on board the Atmospheric Dynamic Mission (ADM)-Aeolus satellite. Quality control procedures were developed to assess the HLOS wind data quality, and observation operators added to the KIM three-dimensional variational data assimilation system to support the new observed variables. In a global cycling experiment, assimilation of ALADIN observations led to reductions in average root-mean-square error of 2.1% and 1.3% for the zonal and meridional wind analyses when compared against European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) analyses. Even though the observable variable is wind, the assimilation of ALADIN observation had an overall positive impact on the analyses of other variables, such as temperature and specific humidity. As a result, the KIM 72-hour wind forecast fields were improved in the Southern Hemisphere poleward of 30 degrees.