• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1763_1764
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• 2009

관성항법시스템에서는 항법을 수행하기 전 항체의 자세를 구하는 정렬을 수행하여야 한다. 본 논문에서는 추정치 기반의 섭동모델인 Psi각 오차모델을 이용하여 정밀 정렬을 수행하는 알고리즘을 제시하고 모의실험을 통하여 정렬 오차가 예상 결과 범위 내로 추정됨을 확인하였다.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.361-370
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• 2004

The DSN(Deep Space Network) measurement model for interplanetary navigations which is essential for precise orbit determination has been developed. The DSN measurement model produces fictitious DSN observables such as range, doppler and angular data, containing the potential observational errors in geometric data obtained from orbit propagator. So the important part of this research is to model observational errors in DSN observation and to characterize the errors. The modeled observational errors include the range delay effect caused by troposphere, ionosphere, antenna offset, and angular refraction effect caused by troposphere. Non-modeled errors are justified as the parameters. All of these results from developed models show about $10\%$ errors compared to the JPL's reference results, that are within acceptable error range.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.89-101
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• 2015

This paper proposes a statistical model of 3-D positions when tracking moving targets using the uncooled infrared (IR) stereo camera system. The proposed model is derived from two errors. One is the position error which is caused by the sampling pixels in the digital image. The other is the timing jitter which results from the irregular capture-timing in the infrared cameras. The capture-timing in the IR camera is measured using the jitter meter designed in this paper, and the observed jitters are statistically modeled as Gaussian distribution. This paper derives an integrated probability distribution by combining jitter error with pixel position error. The combined error is modeled as the convolution of two error distributions. To verify the proposed statistical position error model, this paper has some experiments in tracking moving objects with IR stereo camera. The 3-D positions of object are accurately measured by the trajectory scanner, and 3-D positions are also estimated by stereo matching from IR stereo camera system. According to the experiments, the positions of moving object are estimated within the statistically reliable range which is derived by convolution of two probability models of pixel position error and timing jitter respectively. It is expected that the proposed statistical model can be applied to estimate the uncertain 3-D positions of moving objects in the diverse fields.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.3
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• pp.245-254
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• 2000

This paper proposes a new discrete curvature error metric to generate LOD meshes. For mesh simplification, discrete curvatures are defined with geometric attributes, such as angles and areas of triangular polygonal model, and dihedral angles without any smooth approximation. They can represent characteristics of polygonal surface well. The new error metric based on them, discrete curvature error metric, increases the accuracy of simplified model by preserving the geometric information of original model and can be used as a global error metric. Also we suggest that LOD should be generated not by a simplification ratio but by an error metric. Because LOD means the degree of closeness between original and each level's simplified model. Therefore discrete curvature error metric needs relatively more computations than known other error metrics, but it can efficiently generate and control LOD meshes which preserve overall appearance of original shape and are recognizable explicitly with each level.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.449-449
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• 2022

제주도는 용수의 대부분을 지하수에 의존하므로 지하수위의 예측 및 관리는 매우 중요한 사항이다. 제주도의 지층은 화산활동에 의한 현무암이 겹겹이 쌓여있는 형태를 나타내며 육지의 지층구조와 매우 다른 복잡한 형태를 나타낸다. 이에 따라 제주도 지하수위의 예측은 매우 난해하며, 최근에는 딥러닝 인공지능 모델을 활용하여 지하수위를 예측하는 연구사례가 증가하고 있다. 기존의 연구들은 인공지능 모델들이 지하수위를 적절히 예측한다고 보고하고 있으나 예측의 적절성에 대한 판단기준을 제시하지 못하였으므로 이에 대한 명확한 제시가 필요하다. 본 연구의 목표는 인공지능을 활용한 지하수위 예측오차가 허용 가능한지 판단할 수 있는 기준을 제시함에 있다. 이를 위해 전 세계의 과거 20년 동안 관련 연구결과들을 수집 및 분석하였으며, 분석 결과 인공지능 모델의 지하수위 예측오차는 지하수위 변동성이 큰 지역일수록 증가하는 것을 확인하였다. 이것은 지하수위의 변동형태가 크고 복잡할수록 인공지능 모델의 지하수위 예측성능은 낮아진다는 것을 의미한다. 이 관계를 명확하게 나타내기 위해 지하수위 최대변동폭과 평균제곱근오차 및 최대오차와의 관계를 선형회귀식으로 도출하여 허용가능한 예측오차 기준을 제시하였다. 그리고 기존 연구들에서 제시한 Nash-Sutcliffe 효율성지수와 결정계수를 분석하여 선형회귀식에 의한 기준을 보완할 수 있는 추가적인 기준을 제시하였다. 본 연구에서 제시한 인공지능 모델에 의한 지하수위 예측결과의 적절성 판단기준은 향후 지속적으로 증가하는 인공지능 예측연구에 유용하게 사용될 수 있다.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.45-48
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• 2005

Study on the thermal pointing error analysis for optical bench was performed in this paper. Spacecraft FEM is necessary to conduct thermal pointing error analysis for optical bench. But generally during the preliminary design, exact spacecraft FEM does not exist. So the analysis method to predict thermal pointing error of spacecraft is necessary without exact spacecraft FEM. In this study, these analysis techniques are described.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.5
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• pp.459-466
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• 2012

The ionospheric delay is the largest error source in GPS positioning after the SA effect has been turned off. The ionospheric error can be easily removed by using ionospheric-free combinations but it is only restricted for dual-frequency receivers. Therefore, in this study, the regional ionospheric grid model was developed for single-frequency receivers. The developed model was compared with GIM to validate its accuracy. As a result, it yielded RMSE of 3.8 TECU for 10 days. And L1 medium- and long-range relative positioning was performed to evaluate positioning accuracy improvements. The positioning accuracy was improved by 46.7% compared with that without any correction of ionosphere and troposphere and was improved by 14.5% compared with that only tropospheric correction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.12
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• pp.1232-1237
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• 2009

The ICAO and FAA are developing and verifying of GBAS for civil aircraft landing and take-off. The guarantee of aircraft integrity issue is the important part of GBAS. To guarantee integrity, the GBAS ground facility broadcasts various informations to aircraft. The informations are related to the estimated accuracy of each pseudorange correction and the estimated error terms, for example B-value and standard deviation of the ground facility error. These parameters are used to calculate position error (estimated value of the user). If estimated position errors don't satisfy requirements, aircraft use alternate navigation means. In this paper, GBAS reference stations's real data, which operated by KARI (Korea Aerospace Research Institute) in Jeju international airport, are used to development of new ground facility error standard deviation model. We verify improvement of GBAS availability, with respected to vertical protection level, using B-value based a new ground facility error standard deviation model and a sigma inflation factor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.4
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• pp.47-56
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• 2005

In GPS/INS/barometer navigation system for UAV, vertical channel damping loop was introduced to suppress divergence of the vertical axis error of INS, which could be reduced to the level of accuracy of pressure altitude measured by a pitot-static tube. Because static pressure measured by the pitot-static tube depends on the speed and attitude of the vehicle, static pressure error models, based on aerodynamic data from wind tunnel test, CFD analysis, and flight test, were applied to reduce the error of pressure altitude. Through flight tests and sensitivity analyses, the error model using the ratio of differential pressure and static pressure turned out to be superior to the model using only differential pressure, especially in case of high altitude flight. Both models were proposed to compensate the effect of vehicle speed change and used differential and static pressure which could be obtained directly from the output of pressure transducer.

• Journal of IKEEE
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• v.11 no.4
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• pp.137-144
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• 2007

Fire Control System(FCS) errors can be classified as hardware errors and software errors, and one of the software errors is from target tracking filter which estimates target's location, velocity, acceleration, and so on. It affects function of ballistic calculation equipment significantly. For gun to form predicted hitting point accurately and enhance hitting rate, we need status information of target's future location. Target tracking filter algorithms consist of Single Singer Model, Fixed Gain filter algorithm, IMM, PBIMM and so on. This paper will design IMM tracking filer, which is going to be! applied to domestic warship. Target tracking filter using CV model, Song model and CRT model for IMM tracking filter is made, and tracking ability is analyzed through Monte-Carlo simulation.