• Journal of Advanced Navigation Technology
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• v.8 no.1
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• pp.26-37
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• 2004

Consistent and realistic error covariance information is important for position estimation, error analysis, fault detection, and integer ambiguity resolution for differential GNSS. In designing a position domain carrier-smoothed-code filter where incremental carrier phases are used for time-propagation, formulation of consistent error covariance information is not easy due to being bounded and temporal correlation of propagation noises. To provide consistent and correct error covariance information, this paper proposes two recursive filter algorithms based on carrier-smoothed-code techniques: (a) the stepwise optimal position projection filter and (b) the stepwise unbiased position projection filter. A Monte-Carlo simulation result shows that the proposed filter algorithms actually generate consistent error covariance information and the neglection of carrier phase noise induces optimistic error covariance information. It is also shown that the stepwise unbiased position projection filter is attractive since its performance is good and its computational burden is moderate.

• Journal of Advanced Navigation Technology
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• v.16 no.4
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• pp.602-610
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• 2012

Ionospheric delay error, one of main error sources in GPS signal, varies with signal frequency. Dual-frequency user uses L1, L2 frequency pseudorange to estimate the ionospheric delay, and there are errors caused by pseudorange measurement noise. So, filter is usually used to smooth the measurement. Weighted hatch filter can estimate optimal smoothed pseudorange measurement. But measurement noise model is needed to use this filter. In this paper, measurement noise modeling is conducted for NDGPS reference station. Using noise modeling result, weighted hatch filter estimate smoothed pseudorange measurement and ionospheric delay. Standard deviation of ionospheric dealy error drops to one-twenty fifth of non-filtered result.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.371-382
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• 2004

To improve the precision of relative positioning for GPS single frequency(L1) receiver, we accomplished the GPS data processing using the weighted smoothing techniques. The weighted phase smoothing technique is used to minimize the measurement error of pseudorange and position domain smoothing technique is adopted to make the complement of cycle-slip affection. we also considered some component errors like as ionospheric error, which are related with baseline length, and processed for several baselines (5, 10, 30, 40, and 150 km) to check the coverage area of this algorithm. This paper shows that weighted phase smoothing technique give more stable results after using this technique and the position domain smoothing technique can reduce the errors which are sensitive to the observational environment. Based on the results, we could find out that this algorithm is available for post-time and real-time applications and these techniques can be substitution methods which is able to get the high accuracy and precision without resolving the Integer ambiguity.

• Proceedings of the Korea Multimedia Society Conference
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• 2000.04a
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• pp.184-189
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• 2000

역 해프토닝의 성능을 향상시키려면 최적의 평활화마스크가 생성되어야하고, ？거의 평활화 마스크를 생성하기 위해서는 정확한 해프톤 셀 정보가 구해져야한다. 이에 본 논문에서는 퓨리에 공간에서 가우시안 보간법에 의해 구해진 피크위치를 이용해서 해프톤 셀 정보의 초기값을 설계하고 spatial 공간에서 셀크기, 각도 및 offset을 미세조정하면서 , 반복연산 (iteration )을 통한 해프톤 셀정보 추출방법을 제안한다. 제안한 방법으로 구한 해프톤 셀 정보를 이용하면 최적의 평활화 마스크를 만들 수 있으며 , 영상의 원점에서 멀리 떨어져 오차가 많이 누적되는 부분에서도 해프톤 셀 중심(seed pixel)을 정확하게 구하는 것을 실험을 통해 확인하였다. 제안한 방법은 평활화 마스크를 만들기 위한 정보로 사용될 뿐만 아니라 , 해프톤 셀단위의 연산이나, 퓨리에 공간의 피크 정보를 이용하여 텍스쳐 패턴을 찾는 분야등에 유용하게 활용할 수 있다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.1
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• pp.79-88
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• 2018

With the increasing popularity of electronic toll collection system using 5.8 GHz dedicated short-range communications (DSRC) technology, DSRC-based travel-time collection systems have been deployed on major urban and rural arterial routes in Korea. However, since probe sample sizes are frequently insufficient in probe-based systems, the gathered travel times from probe vehicles fluctuate significantly compared to those of the population; as a result, the accuracy of the collected travel times could decrease. To mitigate the fluctuations (also known as biases), smoothing techniques need to be applied. In this study, some smoothing techniques-moving average, the Loess, and Savitzky-Golay filtering-were applied to probe travel times. Resultantly, the error in the smoothed travel times at the lowest sampling plan (5%) decreased as much as 45% compared to those in non-smoothed travel times. The results of this study can be practically applied to probe-based travel-time estimation systems for providing reliable travel times along the travel corridor.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.937-945
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• 2000

The assessment of machined surface is difficult because the freeform surface must be evaluated by surface fairness as well as dimensional accuracy. In this study, the machined freeform surface is modeled by interpolating the data measured on the machine tool into the mathematical continuous surface, and then the surface model is improved with the parameterization to minimize surface fairness. The accuracy reliability of the measured data is confirmed through compensation of volumetric errors of the machine tool and of probing errors. Non-uniform B-spline surface interpolation method is adopted to guarantee the continuity of surface model. Surface fairness is evaluated with the consideration of normal curvature on the interpolated surface. The validity and usefulness of the proposed method is examined through computer simulation and experiment on the machine tool.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.2
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• pp.149-157
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• 2004

Implicit finite element analysis of the flat surface-straight edge hemming process is performed by using a commercial code ABAQUS/Standard. Methods of finite element modeling for springback simulation and contact pair definition are discussed. An optimal mesh system is chosen through the error analysis that is based on the smoothing of discontinuity in the state variables. This study has focused on the investigation of the influence of process parameters in flanging, pre-hemming and main hemming on final hem quality, which can be defined by turn-down, warp and roll-in. The parameters adopted in this parametric study are flange length, flange angle, flanging die corner radius, face angle and insertion angle of pre-hemming punch, and over-stroke of pre-hemming and main hemming punches.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.502-502
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• 2015

현재 기상레이더로부터 제공되고 있는 레이더 자료의 공간해상도는 $1^{\circ}{\times}250m$, 시간해상도는 10 분으로 보통 기상 및 수문분야에서는 10 분 이상의 $1km{\times}1km$의 격자 자료를 활용하고 있다. 그러나 이와 같은 크기의 해상도는 중규모 이상의 유역에서의 강우-유출 해석에 적합할지 모르나 이보다 고해상도의 자료를 요구하는 도시 유역과 같은 소규모 유역에서는 한계점이 있어왔다. 또한 너무 높은 해상도 자료를 강우-유출 과정에 입력하게 되면 레이더 강우 자료에 내포되어 있는 무작위 오차로 인해 강우-유출의 오차가 커지게 된다. 반면 너무 낮은 해상도 자료를 강우유출과정에 입력하게 되면 강우의 공간적인 특성이 평활화되고 이로 인해 레이더 강우 자료는 분포형 강우 자료로써의 기능을 잃게 된다. 이에 적절한 시공간 해상도 결정을 위해 공간 해상도에 따른 도시홍수모형의 입력 자료를 분석하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.204-209
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• 1999

In general, neural networks are widely used for the category classification. But when low contrast images, such as multispectral images, are used as the input of neural networks, neural networks converge very slowly and are of bad performance. To overcome this problem, we propose a new image enhancement method which consists of smoothing process, finding the main valley and enhancement process. And the enhanced images by the proposed method are used as the input of neural networks for the category classification. When the new category classification method is applied to multispectral LANDSAT TM images, we verified that neural networks converge very fast and overall category classification performance is improved.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.2 s.314
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• pp.55-62
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• 2007

This paper proposes method to get exquisite third dimension data removing included noise by error that occur in third dimension reconstruction through camera auto-calibration. Though reconstructing third dimension data by previous noise removing method, mesh that area is wide is happened problem by noise. Because mesh's area is important, the proposed algorithm need preprocessing that remove unnecessary triangle meshes of acquired third dimension data. The research analyzes the characteristics of noise using the area information of 3-dimensional meshes, separates a peek noise and a Gauss noise by its characteristics and removes the noise effectively. We give a quantitative evaluation of the proposed preprocessing filter and compare with the mesh smoothing procedures. We demonstrate that our effective preprocessing filter outperform the mesh smoothing procedures in terms of accuracy and resistance to over-smoothing.