• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.4
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• pp.411-420
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• 2009

To plan a GPS survey, they have to decide if a survey can be conducted at a specific point and time based on the predicted GPS ephemeris. In this study, to predict ephemeris, we used the repeat time of a GPS satellite. The GPS satellite repeat time was determined by analysing correlation among three-dimensional satellite coordinates provided by the 48-hour GPS ephemeris in the ultra-rapid orbits. By using the calculated repeat time and Lagrange interpolation polynomials, we predicted GPS orbits f3r seven days. As a result, the RMS of the maximum errors in the X, Y, and Z coordinates were 39.8 km 39.7 km and 19.6 km, respectively. And the maximum and average three-dimensional positional errors were 119.5 km and 48.9 km, respectively. When the maximum 3-D positioning error of 119.5 km was translated into the view angle error, the azimuth and elevation angle errors were 9.7'and 14.9', respectively.

• Journal of Korean Society for Geospatial Information Science
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• v.14 no.3 s.37
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• pp.47-53
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• 2006

In this contribution, an integration of seamless navigation system for the pedestrian is introduced. To overcome the GPS outages in various situations, multi-sensor of GPS, INS, electronic barometer and compass are considered in one Extented Kalman filter. Especially, the integrated system is designed for low-cost for the practical applications. Therefore, a MEMS IMU is considered, and the low quality of the heading is compensated by the electronic compass. In addition, only the pseudoranges from GPS measurements are considered for possible real-time application so that the degraded height is also controlled by a barometer. The mathematical models for each sensor with systematic errors such as biases, scale factors are described in detail and the results are presented in terms of a covariance analysis as well as the position and attitude errors compared to the high-grade GPS/INS combined solutions. The real application scenario of GPS outage is also investigated to assess the feasible accuracy with respect to the outage period. The description on the current status of the development and future research directions are also stated.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.3
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• pp.115-122
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• 2015

Global Positioning System (GPS) is used in various fields such as communications systems, transportation systems, e-commerce, power plant systems, and up to various military weapons systems recently. However, GPS receiver is vulnerable to jamming signals as the GPS signals come from the satellites located at approximately 20,000 km above the earth. For this reason, various anti-jamming techniques have been developed for military application systems especially and it is also required for commercial application systems nowadays. In this paper, we proposed a dual-channel Global Navigation Satellite System (GNSS) RF ASIC for digital pre-correlation anti-jam technique. It not only covers all GNSS frequency bands, but is integrated low-gain/attenuation mode in low-noise amplifier (LNA) without influencing in/out matching and 14-bit analogdigital converter (ADC) to have a high dynamic range. With the aid of digital processing, jamming to signal ratio is improved to 77 dB from 42 dB with proposed receiver. RF ASIC for anti-jam is fabricated on a 0.18-μm complementary metal-oxide semiconductor (CMOS) technology and consumes 1.16 W with 2.1 V (low-dropout; LDO) power supply. And the performance is evaluated by a kind of test hardware using the designed RF ASIC.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.1
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• pp.51-56
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• 2003

Microwave dielectric properties of the $MgTiO_3-CaTiO_3$ ceramics were investigated for GPS antenna fabrication. (1-X) $MgTiO_3-X CaTiO_3$ ceramics with X=7 mol% sintered at $1400^{\circ}C$ exhibited can be dielectric constant of 20.6, the quality factor of 52,500 and the temperature coefficient of resonant frequency of -1.5 [ppm/$^{\circ}C$]. The results of $0.93MgTiO_3-0.070CaTiO_3$ ceramics with $P_2O_5$/ 0.6 wt% sintered at $1250^{\circ}C$ exhibited can be dielectric constant of 21, the quality factor of 58,000 and the temperature coefficient of resonant frequency of 2.6 [ppm/${\circ}C$]. The size, insertion loss, center frequency and band width of GPS antenna were $20.5{\times}20.5{\times}6[mm]$,-10(dB) and 1575.42(MHz) respectively. The insertion loss, center frequency and band width of the fabricated GPS antenna were -11 (dB), 1579(MHz) and 22(MHz) respectively. The center frequency was higher than design result, but other characteristics of GPS antenna were similar to the results of design result.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.181-189
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• 2001

This paper describes the positioning accuracy of GPS moduls (KGP9800C, KiRyung) which need to record the operating position of fishing boat as realtime processing in order to develope auto recording system of fishing boat's operating information, and then it's positioning accuracy for DGPS receiver (MGP-100D, Shin-A) and DGPS beacon (GP-36, Furuno) were analyzed. Futhermore, it was examined the positioning error of the GPS module with processing algorithm to minimize the effect of the signal fluctuations. The results indicate that the positioning error is able to decrease 5m as 2drms, and such improvement of positioning performance for GPS module (KGP9800C) can be provide the basic design data in the development of the auto recording system of fishing boat's operating information.

• Journal of Navigation and Port Research
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• v.29 no.8 s.104
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• pp.763-770
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• 2005

Global Navigation Satellite System (GNSS) has become an indispensable tool for providing precise position, velocity and time information for many applications like traditional surveying and navigation etc. However, Global Positioning System (GPS), which was developed and is maintained and operated by the U.S. Department of Defence (DoD), has monopolized the world industry and market, and hence there exists the situation that most of GNSS users absolutely depend upon the GPS. In order to overcome the monopoly, some countries, such as Russia, Japan and European Union (EU), have developed their own GNSSs, so-called GLONASS, JRANS and Galileo systems. Among them, the most prospective system in near future is EU's Galileo system scheduled to launch in 2008. This research has focused on the next generation GNSS system based on GPS and Gralileo system with developing a GNSS simulation software, named as GIMS2005, which generates and analyzes satellite constellation and measurements. Based on the software, a variety of simulation tests have been carried out to recognize limits of GPS-only system and potential benefits of integrated GPS/Galileo positioning. Geometry simulation results have showed that comparing with GPS-only case, the number qf visual satellites, Dilution of Precision (DOP) values, internal reliabilities and external reliabilities.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.140-148
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• 2012

For autonomous navigation, map, pose tracking, and finding the shortest path are required. Because there is no GPS signal in indoor environment, the current position should be recognized in the 3D map by using image processing or something. In this paper, we explain 3D map creation technology by using depth camera like Kinect and pose tracking in 3D map by using 2D image taking from camera. In addition, the mechanism of avoiding obstacles is discussed.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.145-148
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• 1998

In this paper, a microstrip antenna is designed using a rectangular patch. To find characteristics of the antenna, computer simulations of the rectangular single microstrip patch antenna are performed with changing width. And we compared the result of computer simulation with the experimental value. Through the results, we found that the 3-D FDTD method is an effective method for designing microstrip patch antenna. According to simulation the resonant point has been found it in the frequency received from GPS satellite. It is thought that make it match by adjusting the feedpoint.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.517-519
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• 2004

GPS(Global Positioning System)은 위성에서 현재 시스템이 위치한 곳의 주위 지역을 2차원으로 표현해 주는 시스템이다. 이 시스템에서의 그래픽 표현은 비트맵 표현 방식으로 다량의 메모리를 사용하는 단점이 있다. 이 논문에서는 GPS의 다량의 메모리를 사용하는 단점을 보완하기 위하여 비트맵 표현 방식을 지양하고 벡터 표현 방식을 사용하는 SVG(Scalable Vector Graphic)를 이용하며 메모리 사용량을 감소시킬 수 있는 방법을 제시하고자 한다. 또한 XML의 그래픽 표준안인 SVG에서는 2차원만을 표시하기 때문에 3차원 표현이 어려우나, ECMAScript를 사용하여 SVG의 단정인 3자원 표현의 어려움을 개선하는 방법에 대해 고찰하고자 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.04a
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• pp.581-584
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• 2015

드론은 GPS 포인트를 기반으로 무인비행이 가능하다. 이 특징을 활용하는 방안의 하나로서, 우리는 해양사고에서의 인명구조를 대상으로 하였다. 구명조끼를 GPS 신호발생기로 구현하고, 이를 이용한 웨이포인트를 설정함으로써, 드론으로하여금 재난자에게 우선 접근할 수 있도록 구현할 수 있다. 이를 실제 구현하기 위해서는 GPS 신호를 드론의 웨이포인트값으로 바꾸어 넣어주는 소프트웨어적 모듈이 요구되며, 본 연구에서 이를 구현하고자 한다. 우리는 3D 로보틱스의 Quadcopter와 그를 지원하는 Pixhawk를 사용하였다.