• Korean Journal of Agricultural and Forest Meteorology
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• v.4 no.4
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• pp.203-212
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• 2002

This study was conducted to remove the urban heat island effects embedded in the interpolated surfaces of daily minimum temperature in the Korean Peninsula. Fifty six standard weather stations are usually used to generate the gridded temperature surface in South Korea. Since most of the weather stations are located in heavily populated and urbanized areas, the observed minimum temperature data are contaminated with the so-called urban heat island effect. Without an appropriate correction, temperature estimates over rural area or forests might deviate significantly from the actual values. We simulated the spatial pattern of population distribution within any single population reporting district (city or country) by allocating the reported population to the "urban" pixels of a land cover map with a 30 by 30 m spacing. By using this "digital population model" (DPM), we can simulate the horizontal diffusion of urban effect, which is not possible with the spatially discontinuous nature of the population statistics fer each city or county. The temperature estimation error from the existing interpolation scheme, which considers both the distance and the altitude effects, was regressed to the DPMs smoothed at 5 different scales, i.e., the radial extent of 0.5, 1.5, 2.5, 3.5 and 5.0 km. Optimum regression models were used in conjunction with the distance-altitude interpolation to predict monthly normals of daily minimum temperature in South Korea far 1971-2000 period. Cross validation showed around 50% reduction in terms of RMSE and MAE over all months compared with those by the conventional method.conventional method.

• Journal of KIISE
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• v.42 no.2
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• pp.264-271
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• 2015

The general way to use a triangulation method is based on PTMP communication between an object and wireless modules in an environment, which is established by more than three wireless modules, to recognize the location of an object. Thus, this method has a problem that the PTMP-based system can only be applied in an environment where the wireless infra is already established. In order to solve this problem, the PTP communication schemes have been proposed but they are insufficient to generalize because they lack specific verification. In this paper, problems of an existed location estimation algorithm based on PTP communication are analyzed, and we propose a location estimation algorithm of a fixed object that satisfyies the condition of a single receiver being substituted to multiple receivers. A location estimation system we designed and implemented using CSS wireless communication modules to evaluate the proposed algorithm. We verify, by experimental results, that the optimum moving interval for the location estimation is 3m in indoor environment of $10m{\times}16m{\times}1m$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1288-1293
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• 2014

This paper proposes a new method to estimate the striking velocity for ballistic limit velocity in MIL-STD-662F. The method from MIL-STD-662F needs relative air density, drag coefficient, form factor, ballistic coefficient for estimating striking velocity. So precedent studies are essential. However, the new method can estimate striking velocity only using measured velocities and distance between the screen and the target. To prove new method, we compared estimation of striking velocity from both the new method and the method from MIL-STD-662F on the basis of datain PRODAS. The new method shows bigger errors in some velocity ranges. But it could still calculate ballistic limit velocity. It also shows smaller errors in most velocity ranges.

• The Journal of the Acoustical Society of Korea
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• v.21 no.5
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• pp.446-454
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• 2002

This paper presents the Doppler Scanning technique which enables us to detect the relative positions of moving distributed sources using Doppler frequency shift estimate when the moving source consists of distributed sources with different signature frequencies. Doppler frequency shifts of characteristic frequencies of machinery noise sources such as ship's generator and propeller, with tine along CPA (Closest Point of Approach of moving source) are unique, and can be functioned with respect to each source position. Therefore, this technique can be applied to estimate the relative geometrical positions between machinery noise sources. The Extended Kalman Filter (EKF) which has a high frequency resolution with high time resolution, is adopted for improving accuracy of Doppler frequency shift estimate geometric resolution of machinery positions since machinery noise sources show in general low frequency band characteristics with limited spacial distance. The performance of the technique is examined by the numerical simulations and is verified by the experiment using loudspeaker sources on the roof of the car.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.4 s.316
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• pp.1-7
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• 2007

When the sensor geometry is poor, the user position estimate obtained by of GN (Gauss-Newton) method is often diverged in radio navigation. In other to avoid divergence problem QCLS (Quadratic Correction Least Square) method using TDOA (Time Difference of Arrival) measurements is introduced, but the estimation error is somewhat large. This paper presents the modified QCLS method using weighted least square. Since the weighting matrix is influenced by the unknown user position, two-step approach is employed in the proposed method. The weighting matrix is estimated in the first step using least square, and then find user position is obtained using weighted least square. Simulation results show that the performance of the proposed method is superior to the conventional QCLS all over the workspace.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.551-560
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• 2011

Recently, There has been increasing concern about WLAN-based indoor positioning system. Most of the existing WLAN-based positioning systems use a fingerprinting method as a main approach. In the fingerprinting approach, the accuracy of the location of a mobile objects is proportional to the number of reference points. However, depending on the increasing number of reference points in the training phase, it requires more time and effort to create fingerprint database. To solve these problems, we propose the new indoor positioning algorithm that calculate the distance between a mobile objects and an AP using the information of surrounding environment WLAN based APs and applied the particle filter to the proposed algorithm in order to improve the accuracy of the estimated location in this paper. To implement this algorithm, at first environmental information database such as wall, iron door, glass door, partition etc. existing in the periphery of the AP should be established. The positioning use attenuation model and path loss model. Our experimental results with proposed algorithm are verified that the positioning accuracy was low but solved the problems with fingerprinting, compared with other positioning algorithms.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.353-360
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• 2012

This paper describes a SLAM method which estimates landmark locations and robot pose simultaneously. The particle filter can deal with nonlinearity of robot motion as well as the non Gaussian property of robot motion uncertainty and sensor error. The state to be estimated includes the locations of landmarks in addition to the robot pose. In the experiment, four beacons which transmit ultrasonic signal are used as landmarks. The robot receives the ultrasonic signals from the beacons and detects the distance to them. The method uses rang scanning sensor to build geometric feature of the environment. Since robot location and heading are estimated by the particle filter, the scanned range data can be converted to the geometric map. The performance of the method is compared with that of the deadreckoning and trilateration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.88-95
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• 2015

This paper presents the study of the efficient localization algorithm for non-linear least square estimation. Although non-linear least square(NLS) estimation algorithms are more accurate algorithms than linear least square(LLS) estimation, NLS algorithms have more computation loads because of iterations. This study proposed the efficient algorithm which reduced complexity for small accuracy loss in NLS estimation. Simulation results show the accuracy and complexity of the localization system compared to the proposed algorithm and conventional schemes.

• Proceedings of the Korean Society of Computer Information Conference
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• 2009.01a
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• pp.313-320
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• 2009

본 논문은 옥내 이동객체 데이터베이스의 갱신 전략을 제안한다. 제안하는 방법은 최근의 일련의 측정치에 칼만 필터를 적용하여 이동객체의 속도를 예측하고, 예측한 속도를 최근 측정치에 적용하여 현재 위치를 추정한다. 그리고 현재 위치로 추정된 값과 현재 실측값의 차이가 일정 거리 이하이면 실측값을 전송하지 않는다. 제안하는 방법의 효율성을 검증하기 위하여 실험 공간을 실제로 걸어가면서 측정한 일련의 측정치에 제안하는 방안을 적용하여 전송을 절약하는 비율과 이로 인한 오차의 증가율을 분석한다.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.22.2-22.2
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• 2011

이 연구에서는 한반도 상공의 전리층 총전자수를 격자 형태로 나타냈다. 이를 위해 국토해양부 GPS 상시관측소에서 제공 중인 코드와 위상 측정값을 선형조합하였으며 그 결과물을 이용하여 시선방향 총전자수를 산출하였다. 이때 전리층 총전자수 산출결과의 정확도를 향상시키기 위해 가중최소자승법을 이용하여 위성과 수신기의 하드웨어 오차인 DCB(Differencial Code Bias)를 추정하였으며 추정된 DCB값은 IGS에서 제공 중인 DCB값과 비교하여 정확도를 확인하였다. 산출된 시선방향 총전자수를 연직방향 총전자수로 변환하기 위해 사상함수를 적용하였으며, 이를 다시 각 격자점에서의 연직방향 총전자수로 변환하기 위해 기존 연직방향 총전자수에 역거리 가중 보간법을 적용하였다. 각 격자점에서의 총전자수는 IGS(International GNSS Service)에서 제공 중인 GIM(Global Ionosphere Map) 모델의 총전자수와 비교하여 정확도를 확인하였다. 산출된 총전자수는 2시간 간격으로 나타내어 한반도 상공 전리층 총전자수의 변화 경향을 확인하였다.