• Journal of Institute of Control, Robotics and Systems
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• v.13 no.1
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• pp.72-78
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• 2007

Determination of the local vertical is not trivial for a moving vehicle and in general will require corrections for the Earth geophysical deflection. The vehicle's local vertical can be estimated by INS integration with initial alignment in SDINS(Strap Down INS) system. In general, the INS has drift error and it cause the performance degradation. In order to compensate the drift error, GPS/INS augmented system is widely used. And in the event that GPS is denied or unavailable, celestial navigation using star tracker can be a backup navigation system especially for the military purpose. In this celestial navigation system, the vehicle's position determination can be achieved using more than two star trackers, and the accuracy of position highly depends on accuracy of local vertical direction. Modern tilt sensors or accelerometers are sensitive to the direction of gravity to arc second(or better) precision. The local gravity provides the direction orthogonal to the geoid and, appropriately corrected, toward the center of the Earth. In this paper the relationship between direction of center of the Earth and actual gravity direction caused by geophysical deflection was analyzed by using precision orbit simulation program embedded the JGM-3 geoid model. And the result was verified and evaluated with mathematical gravity vector model derived from gravitational potential of the Earth. And also for application purpose, the performance variation of pure INS navigation system was analyzed by applying precise gravity model.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.2
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• pp.99-115
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• 2020

Since GNSS is easily affected by jamming and/or spoofing, alternative navigation systems can be operated as backup system to prepare for outage of GNSS. Alternative navigation systems are being researched over the world, and a multi-radio integrated navigation system using alternative navigation systems such as KNSS, eLoran, Loran-C, DME, VOR has been researched in Korea. Least Square or Kalman filter can be used to estimate navigation parameters in the navigation system. A large number of measurements of the Kalman filter may lead to heavy computational load. The decentralized Kalman filter and the federated Kalman filter were proposed to handle this problem. In this paper, the decentralized Kalman filter and the federated Kalman filter are designed for the multi-radio integrated navigation system and the performance evaluation result are presented. The decentralized Kalman filter and the federated Kalman filter consists of local filters and a master filter. The navigation parameter is estimated by local filters and master filter compensates navigation parameter from the local filters. Characteristics of three Kalman filters for a linear system and nonlinear system are investigated, and the performance evaluation results of the three Kalman filters for multi-radio integrated navigation system are compared.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.6
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• pp.719-725
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• 2013

In this paper, we propose a local path planning method based on RANGER algorithm and autonomy manager for autonomous navigation of UGV in urban environment. LPP method is designed to generate the local path in sensing area by using lane and curb of pavement and autonomy manager is designed to make a decision which transit the status of LPP component to a proper status for current navigation environment. A field test is conducted with scenarios in real urban environment in which crossroad, crosswalk and pavement are included and the performance of proposed method is validated.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.182-184
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• 2019

Ports are responsible fro the creation of positive and negative impacts towards the city. The study's contribution focuses on empirically evaluating the perception of Busan citizens of the local port through an application of Q methodology.

• Journal of Information Management
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• v.38 no.3
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• pp.59-80
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• 2007

In this study, we analyzed the web site navigation of law school libraries in terms of global, local, context, support navigation. The recommendations for good web site design were as follows. First, global navigation should provide the consistent navigation and be able to access to the important site and function. Second, quick links of local navigation need to provide the movement of scroll bar. The number of menu and type of link in context navigation should provide the least number. Finally, the site map and index should provide with qualified contents and minimal errors.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.21 no.2
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• pp.29-38
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• 2010

In this study, we analyzed the navigation systems in terms of global, local, Ad-hoc Navigation, and support navigation system using the 35 children's library websites. The study showed that the number of menu, retrieval interface, quick links need to be improved. These results can be used as a framework for designing children's library websites.

• Journal of Positioning, Navigation, and Timing
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• v.8 no.2
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• pp.79-85
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• 2019

The mission tasks of polar exploration utilizing unmanned systems such as glacier monitoring, ecosystem research, and inland exploration have been expanded. To facilitate unmanned exploration mission tasks, precise and robust navigation systems are required. However, limitations on the utilization of satellite navigation system are present due to satellite orbital characteristics at the polar region located in a high latitude. The orbital inclination of global positioning system (GPS), which was developed to be utilized in mid-latitude sites, was designed at $55^{\circ}$. This means that as the user is located in higher latitudes, the satellite visibility and vertical precision become worse. In addition, the use of satellite-based wide-area augmentation system (SBAS) is also limited in higher latitude regions than the maximum latitude of signal reception by stationary satellites, which is $70^{\circ}$. This study proposes a local-area augmentation system that additionally utilizes Global Navigation Satellite System (GLONASS) considering satellite navigation system environment in Polar Regions. The orbital inclination of GLONASS is $64.8^{\circ}$, which is suitable in order to ensure satellite visibility in high-latitude regions. In contrast, GLONASS has different system operation elements such as configuration elements of navigation message and update cycle and has a statistically different signal error level around 4 m, which is larger than that of GPS. Thus, such system characteristics must be taken into consideration to ensure data integrity and monitor GLONASS signal fault. This study took GLONASS system characteristics and performance into consideration to improve previously developed fault detection algorithm in the local-area augmentation system based on GPS. In addition, real GNSS observation data were acquired from the receivers installed at the Antarctic King Sejong Station to analyze positioning accuracy and calculate test statistics of the fault monitors. Finally, this study analyzed the satellite visibility of GPS/GLONASS-based local-area augmentation system in Polar Regions and conducted performance evaluations through simulations.

• Journal of Navigation and Port Research
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• v.34 no.7
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• pp.517-523
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• 2010

There are enormous challenges in the Istanbul Strait- one of the most important, congested and narrow waterways in the world - from the view point of risk determination and risk mitigation for the local traffic. Previously several traffic parameters such as; traffic volume for local vessels, traffic flow and potential encounters of local traffic, in addition to the possibility of collision, were investigated in order to determine the degree of dangers in the southern entrance of the Istanbul Strait. Furthermore, risky zones were also determined in this waterway. On the basis of the results of those, a group of expert was surveyed. These experts were pilots, Vessel Traffic Services Operators (VTS-O), Local Traffic Vessel Captains and Master Mariners who had several experience of navigation through the Istanbul Strait. In order to assess experts perceptions of danger and to propose further studies based on this survey. The questionnaire was analyzed by using SPSS (Statistical Package for the Social Sciences) program version 13.0. Finally, some differences and/or shares on risk perceptions of expert in the Istanbul Strait are considered.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1867-1870
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• 2005

The celestial navigation is one of alternatives to GPS system and can be used as a backup of GPS. In the celestial navigation system using more than two star trackers, the vehicle's ground position can be solved based on the star trackers' attitude information if the vehicle's local vertical or horizontal angle is given. In order to determine accurate ground position of flight vehicle, the high accurate local vertical angle measurement is one of the most important factors for navigation performance. In this paper, the Earth geophysical deflection was analyzed in the assumption of using the modern electrolyte tilt sensor as a local vertical sensor for celestial navigation system. According to the tilt sensor principle, the sensor measures the tilt angle from gravity direction which depends on the Earth geoid surface at a given position. In order to determine the local vertical angle from tilt sensor measurement, the relationship between the direction of gravity and the direction of the Earth center should be analyzed. Using a precision orbit determination software which includes the JGM-3 Earth geoid model, the direction of the Earth center and the direction of gravity are extracted and analyzed. Appling vector inner product and cross product to the both extracted vectors, the magnitude and phase of deflection angle between the direction of gravity and the direction of the Earth center are achieved successfully. And the result shows that the angle differences vary as a function of latitude and altitude. The maximum 0.094$^{circ}$angle difference occurs at 45$^{circ}$latitude in case of 1000 Km altitude condition.

• Journal of the Korean Institute of Navigation
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• v.20 no.4
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• pp.111-128
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• 1996

This paper is focused on the desirable improvement schemes of the local network of information and telecommunication network. In this study, we examined whether polices of information and telecommunication of government have been carried out a desirable programme to meet the public interest, found out several problems in the these policies. Such problems as follows : (1) a system of local information & telecommunication is developing by a Model of Top-Down. In the present management system, an interest of the public of local society about the local telecommunication network is a much lower level, (2) there is no general controlling roll of the local information & telecommunication, (3) there is no service controlling system of local telecommuni-cation, and (4) there is no organic coordinating system of inter-departments in the central government level. In order to resolve these problems, this study suggests a few desirable sxhemes for the local telecommunication : (1) an establishment of middle-long range planning for the integrated future network of info-telecommunication, (2) an organizing of telecommunication network being suitable for the local characteristics toward B-ISDN.