• Journal of Positioning, Navigation, and Timing
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• 제7권3호
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• pp.175-181
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• 2018

The use of dual-frequency measurements from the Global Navigation Satellite System (GNSS) enables us to observe precise ionospheric total electron content (TEC). Currently, many GNSS reference stations in South Korea provide both GPS and GLONASS data. In the present study, we estimated the grid-based TEC values and relative receiver differential code biases (DCB) from a GNSS network operated by the Korea Astronomy and Space Science Institute. In addition, we compared the diurnal variations in a TEC time series from solutions of the GPS only, the GLONASS only, and combined GPS/GLONASS processing. A significant difference between the GPS only TEC and combined GPS/GLONASS TEC at a specific grid point over South Korea appeared near the solar terminator. It is noted that GLONASS measurements can contribute to observing a variation in ionospheric TEC over high latitude regions.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1999년도 추계학술대회논문집
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• pp.281-291
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• 1999

Productivity of container cranes and gantry cranes is influenced by the performance of crane hardware and cycle time. Cycle time in container handling is influenced by the path of containers and relative positioning of containers. So we have to minimize the sway of containers and spreaders to minimize relative positioning time. And sway minimization is influenced by the skill of workers in manual gantry cranes. In this paper, we will develop anti-sway system using mechanical and electrical method. Proposed hybrid system uses the basic structure of general manual gantry crane. So, it is very useful and effective. Electrical methods are main methods and mechanical methods are auxiliary methods.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1180-1185
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• 2004

The purpose of this study is to develop a Multi-joint rehabilitation system (CMRS : C&R Lab. Multi-joint Rehabilitation System). This study presents the mechanism of rehabilitation system that enables rehabilitation of multi-joint with kinematical analysis for joints of human body. Also, the relative positioning between human subjects and the head part to rehabilitate for the mechanism is based on robotics and anatomy. This study was verified with simulations. Finally, Automation of positioning was realized. Rehabilitation exercises in passive mode were enabled with the results.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.101-111
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• 2023

Many spoofing detection studies have been conducted to cope with the most difficult types of deception among various disturbances of GPS, such as jamming, spoofing, and meaconing. In this paper, we propose a spoofing detection scheme based on elevation masked-relative received power between GPS L1 and L2 signals in a system using a multi-band array antenna. The proposed scheme focuses on enabling spoofing to be normally detected and minimizes the possibility of false detection in an environment where false alarms may occur due to pattern distortion among elements of an array antenna. The pattern distortion weakens the GPS signal strength at low elevation. It becomes confusing to detect a spoofing signal based on the relative power difference between GPS L1 and L2, especially when GPS L2 has weak signal strength. We propose design parameters for the relative power threshold including beamforming gain, the minimum received power difference between L1 and L2, and the patch antenna gain difference between L1 and L2. In addition, in order to eliminate the weak signal strength of GPS L2 in the spoofing detection process, we propose a rotation matrix that sets the elevation mask based on platform coordinates. Array antennas generally do not have high usefulness in commercial areas where receivers are operated alone, but are considered essential in military areas where GPS receivers are used together with signal processing for beamforming in the direction of GPS satellites. Through laboratory and live sky tests using the device under test, the proposed scheme with an elevation mask detects spoofing signals well and reduces the probability of false detection relative to that without the elevation mask.

• 제어로봇시스템학회논문지
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• 제11권7호
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• pp.644-650
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• 2005

The expected positioning accuracies of civil users utilizing modernized GPS and Galileo are derived using the error analysis in this paper. Since, in general, the performance of DLL, PLL and FLL is proportional to chip lengths and wavelengths, the positioning accuracies from various measurements of modernized GPS and Galileo are derived as function of chip length and wavelength. These results are compared with that from GPS Ll measurement. In absolute positioning, compared to GPS C/A code only case, more than 17 times performance improvement is expected when all civil code signals of modernized GPS and Galileo (L1, L2, L5, E1, E5A and E5B) are used. In relative positioning, compared to GPS L1 carrier phase only case, more than 2 times performance improvement is expected when all civil signals of modernized GPS and Calileo are used. Furthermore, the relationship between GDOP and RGDOP in single frequency case is expanded to general case where multiple frequencies and both code and carrier phase measurements are used.

• 한국조리학회지
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• 제13권2호
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• pp.275-291
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• 2007

The growth of foodservice industry has caused keen competition in the family restaurant industry. For a differentiation strategy to be competitive, on the preferential basis, it is necessary for each family restaurant business to analyze its position in the market. Therefore, this study is to certify customers' perceived servicescape and image similarity and analyzes positioning of seven family restaurants. For this research, multidimensional scaling(MDS) is performed to determine how they are positioned relative to competitors. According to the result of the positioning map(ALSCAL and PROFIT map), it is found that Outback steakhouse, T.G.I. Friday's, Bennigans' have more strong competitiveness than VIPS, Marche and Sizzler in servicescape factors and restaurant selection attribute except menu diversity. But the preference order does not follow the order of competitiveness. This result from the positioning map means that each business needs various marketing strategies that cannot be copied easily.

• Imaging Science in Dentistry
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• 제32권3호
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• pp.159-165
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• 2002

Purpose: The aim of this study was to introduce a method of obtaining the oscillation graphs of the dental x-ray tube heads relative to time using an accelerometer. Materials and Methods: An Accelerometer, Piezotron type 8704B25 (Kistler Instrument Co., Amherst, NY, USA) was utilized to measure the horizontal oscillation of the x-ray tube head immediately after positioning the tube head for an intraoral radiograph. The signal from the sensor was transferred to a dynamic signal analyzer, which displayed the magnitude of the acceleration on the Y-axis and time lapse on the X -axis. The horizontal oscillation of the tube head was measured relative to time, and the settling time was also determined on the basis of the acceleration graphs for 6 wall type, 5 floor-fixed type, and 4 mobile type dental x-ray machines. Results : The oscillation graphs showed that tube head movement decreased rapidly over time. The settling time varied with x-ray machine types. Wall-type x-ray machines had a settling time of up to 6 seconds, 5 seconds for fixed floor-types, and 1 I seconds for the mobile-types. Conclusion: Using an accelerometer, we obtained the oscillation graphs of the dental x-ray tube head relative to time. The oscillation graph with time can guide the operator to decide upon the optimum exposure moment after x-ray tube head positioning for better radiographic resolution.

• 한국측량학회지
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• 제29권3호
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• pp.237-247
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• 2011

우리나라의 GPS상시관측소는 1995년 국토지리정보원내에 최초로 설치된 이후, 2011년 현재 72개가 측량과 항법의 기준점으로 설치되어 활용되고 있다. GPS의 기준좌표계는 지심좌표계로써 그 중심은 1년에 약 1mm내외로 극히 작지만 끊임없이 움직이고 있기 때문에 특정 시간에 고정된 좌표계와 GPS데이터로써 그 좌표를 설정하고 있다. 한 국가 내에서 측량과 지도제작 목적으로 사용되는 GPS상시관측소는 상대적인 측량의 기준이기 때문에 국가적인 규약에 따라서 특정 시간대의 좌표계를 설정하여 사용하는 것이 혼란을 방지할 수 있다. 그러나 지심의 변화가 아닌 지각변동에 의한 GPS상시관측소간 기선의 상대적인 변화는 GPS상대측위의 정확도를 저하시키는 원인이 된다. 우리나라는 비교적 안정된 지각으로 구성되어 있다고 판단되어 왔기 때문에 지각변동에 따른 국가 기준점의 성과 갱신을 고려하지 않았다. 본 연구에서는 우리나라 GPS상시관측소 중 40개와 우리나라 주변의 국제 GPS상시관측소 5개를 선정하여 30개월간의 일별 GPS 데이터에 대하여 정밀기선해석을 실시하고, 전세계 130개 IGS GPS상시관측소망과 결합 조정함으로써 우리나라 GPS상시관측소의 연간 변동량을 계산하였다. 이로부터 우리나라 지각변동량의 특성을 분석하고 GPS상시관측소 사이의 상대적인 변동량을 계산하여 GPS상대측위의 기준점 역할수행을 위한 GPS상시관측소의 성과갱신 주기를 분석하고 정밀 GPS상대측위를 위한 한반도 지각변동모델은 개발하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제2권3호
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• pp.171-176
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• 2010

This paper proposes the application of sensor technology to assemble ship blocks efficiently. A sensor-based monitoring system is designed and implemented to improve shipbuilding productivity by reducing the labor cost for the adjustment of adequate positioning between ship blocks during pre-erection or erection stage. For the real-time remote monitoring of relative distances between two ship blocks, sensor nodes are applied to measure the distances between corresponding target points on the blocks. Highly precise positioning data can be transferred to a monitoring server via wireless network, and analyzed to support the decision making which needs to determine the next construction process; further adjustment or seam welding between the ship blocks. The developed system is expected to put to practical use, and increase the productivity during ship blocks assembly.

• 한국통신학회논문지
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• 제40권12호
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• pp.2520-2527
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• 2015

작전을 수행하는 군 환경에서 위치 정보는 매우 중요하다. 군 환경에서 위치 정보 획득은 일반적으로 GPS에 의해 이루어진다. 하지만 GPS는 수신 신호의 세기가 매우 약해 전파교란에 취약하다는 단점이 있다. 이러한 단점을 해결하기 위해 많은 연구가 진행되고 있다. 상대항법은 전술데이터링크 표준인 JTIDS(Joint Tactical Information Distribution System)에서 정의된 GPS 보조항법이다. GPS 전파교란 환경에서 상대항법의 정확한 운용을 위해서는 지상에서 공중노드의 참조노드 역할을 수행하는 GRU(Ground Reference Unit)가 보장되어야한다. 하지만 상대항법을 운용하는데 있어서 GRU를 항상 보장하는 것은 쉬운 일이 아니다. GRU 부재 환경에서 상대항법 운용중인 공중노드는 관성항법장치에 의존하여 측위한다. 하지만 관성항법장치에 의존하는 측위는 시간이 지남에 따라 누적 오차 발생을 야기하며 누적 오차에 의해 공중노드는 정확한 측위를 할 수 없다. 본 논문에서는 상대항법에서 GRU 부재 시 관성항법장치 의존으로 인한 공중노드의 위치 오차를 줄이기 위한 대처 방안을 제시한다. 또한 대체 방안의 성능이 기존의 성능에 비하여 우수하다는 것을 모의실험을 통해 증명한다.