• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.20 no.2
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• pp.171-181
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• 2002

As the result of the analysis of the underground utility map made before, we could have divided the kind of errors into the two types, position error of geometric data and attribute error and knew the fact that mainly position error is derived from the process of detecting and surveying the underground utility, and attribute is inputting data. In this study we showed the way improving accuracy in detecting and surveying underground utility by field test, and the way to reduce attribute error by process refinement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.2102-2112
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• 2015

In this paper, we propose a new positioning scheme for accuracy improvement of Relay-based Navigation System. The conventional relay-based system occurs larger vertical error than horizontal one due to structural characteristics that positioning references are located toward same direction and a location of user is estimated by triangulation technique. In the proposed positioning scheme, the user position is reestimated using an additional virtual reference which is generated based on position information of reference stations in navigation signals and estimated initial user position. The nearest reference station from the estimated user position is selected as a virtual reference to minimize the effect of geometrical factor. The vertical error decreases by using reference points on multi planes, therefore, accurate positioning is possible than the conventional scheme. We demonstrated that the accuracy of a user is improved through simulation results.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.237-244
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• 2007

Estimation of target position is one of the main functions of surveillance UAVs, and is being used to various purposes but generally noisy target position is estimated due to the existence of random measurement errors. In this report, a method of diminishing target position estimation error by calculating target position using Kalman Filtered optimum values such as position, attitude of UAV and sight vector of optical instrument, is proposed.

• Journal of Navigation and Port Research
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• v.37 no.1
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• pp.35-40
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• 2013

In the eLoran navigation system, the dominant deterioration factors of navigation accuracy are the TOA measurement errors on user receiver and the GDOP between the receiver and the transmitters. But if the ASF data measured at dLoran reference station are provided for users through the Loran data channel, it will be possible to correct the TOA measurement errors. The position accuracy can be determined by the DOP depending on the geometry of receiver-transmitters, and their optimal placement improves the navigation accuracy. In this study we determined the geometric placement in case of up to six stations, and evaluated the performance of position accuracy for the receiver-transmitter geometry set of eLoran stations. The proposed geometry of eLoran stations can be referred for the construction of eLoran infrastructure meeting the capability of HEA for maritime, and time/frequency users in Korea.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.308-311
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• 2008

One of the key technical elements of wireless sensor network (WSN) is location management of sensor nodes. Typical node location management methods use GPS, ultrasonic sensors or RSSI. In this paper we propose a new location management method which adopts regression analysis of RSSI measurement to improve the accuracy of sensor node position estimation. We also evaluated the performance of proposed method by comparing the experimental results with existing scheme. According to the results, our proposed method showed better accuracy than existing location management scheme using RSSI and Firis' equation.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 1999.04a
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• pp.334-336
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• 1999

• Journal of the Korean Society of Radiology
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• v.16 no.2
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• pp.151-156
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• 2022

A detector using a small number of photosensors was designed, and the position of a scintillation pixel that interacted with gamma rays through a maximum likelihood position estimation(MLPE) was measured as a digital position. For this purpose, simulation was performed using DETECT2000, which can simulate the movement of light within the scintillator, and the accuracy of position measurement was evaluated. A detector was configured using a 6 × 6 scintillation pixel array and 4 photosensors, and a gamma ray event was generated at the center of each scintillation pixel to create a look-up table through the ratio of acquired light. The gamma-ray event generated at the new position was applied as the input value of the MLPE, and the positiion of the scintillation pixel was converted into a digital positiion after comparison with the look-up table. All scintillation pixels were evaluated, and as a result, a high accuracy of 99.1% was obtained. When this method is applied to the currently usesd system, it is concidered that the process of determining the position of the scintillation pixel will be simplified.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.4
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• pp.325-331
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• 2015

This paper suggests an intersection method to improve the accuracy of three-dimensional position from heterogeneous satellite stereo images, and addresses validation of the suggested method following the experimental results. The three-dimensional position is achieved by determining an intersection point of two rays that have been precisely adjusted through the sensor orientation. In case of conventional homogeneous satellite stereo images, the intersection point is generally determined as a mid-point of the shortest line that links two rays in at least square fashion. In this paper, a refined method, which determines the intersection point upon the ray adjusted at the higher resolution image, was used to improve the positioning accuracy of heterogeneous satellite images. Those heterogeneous satellite stereo pairs were constituted using two KOMPSAT-2 and QuickBird images of covering the same area. Also, the positioning results were visually compared in between the conventional intersection and the refined intersection, while the quantitative analysis was performed. The results demonstrated that the potential of refined intersection improved the positioning accuracy of heterogeneous satellite stereo pairs; especially, with a weak geometry of the heterogeneous satellite stereo, the greater effects on the accuracy improvement.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.6_2
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• pp.635-643
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• 2007

As the availability of images from Airborne Digital Camera with high resolution is expanded, a lot of concern are in the production and update of digital map. This study presents the method of updating the digital map at the scale of 1/1,000 using images from Aerial Digital Camera. Geometric correction was completed using GPS surveying data. For digital mapping, digital photogrammetric system was utilized to digitize buildings and roads. The absolute positional accuracy was evaluated using GPS surveying data and the relative positional accuracy was evaluated using the digital map produced by analytical mapping. The absolute positional accuracy was as follows: RMSE in X and Y were ${\pm}0.172m\;and\;{\pm}0.127m$, and average distance error was 0.208m. The relative positional accuracy was as follows: RMSE in X and Y were ${\pm}0.238m\;and\;{\pm}0.281m$, and average distance error was 0.337m. Accuracies of updating digital map using images from airborne Digital Camera were within allowable error established by NGII. Consequently, images from airborne Digital Camera can be used in various fields including the production of the national basic map and the GIS of local government.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.6
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• pp.443-449
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• 2014

Thermoacoustic (TA) models have been widely used to predict combustion instability characteristics in a gas turbine lean premixed combustor. However, these techniques have shown some limitations in improving the model accuracy related to an over-simplification of the combustion system and flame geometry. Efforts were made in the current study to improve the limitations of the TA models. One strategy was to modify the actual flame location in the model, and another was to consider the heat release distribution through the flames. The modified TA model results show better accuracy in predicting the growth rate of instabilities compared with the previous results.