• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.1
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• pp.10-15
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• 2016

In this study, The code-carrier divergence test was applied to GPS measurements, and the results were compared and analyzed. The GPS data used for the threshold determination were obtained from Global Navigation Satellite System permanent stations built by the Korea Aerospace Research Institute. At each permanent station, identical dual-frequency receiver and choke ring antenna with radome are installed. The analysis method, root mean square values were compared and analyzed for each permanent station and satellite. As a result, the root mean square value generally decreased as the satellite elevation angle increased although the trend was gentle. Threshold were finally selected based on the average and standard deviation of root mean square for each permanent station. For improving of availability and continuity in real-time operation when the threshold is over the limits, Code-Carrier divergence test values are initialized.

• Land and Housing Review
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• v.3 no.1
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• pp.69-78
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• 2012

This study proposes an approach to improve the accuracy of land assessment result focused on the Land Suitability Assessment. The detailed analysis processes are; (a) that they are analyzed considering resistance in distance measurement on the space characteristics of location, and; (b) that an assessment result is measured according to the threshold definition of membership function, which is applied in estimating conservation suitability. The assessment results are; firstly, the method considering resistance better reflects the local characteristics of area with worse accessibility including rivers and mountains than one by linear distance; secondly, the existing method that the maximum value of a target area is defined as the maximum threshold may draw a value evaluated lower than a threshold definition considering the distribution of measured indices. Finally, satellite images are overlapped with the assessed results, the applicability level from the approach proposed by this study is more coincident with the present status. The assessment method proposed by this study can be meaningful in view of that it improves the accuracy of Land Suitability Assessment. Furthermore, it can be applied as SDSS, which can support effective establishment of urban policies, in case of complementing the problems in executing the assessment system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.55-58
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• 2006

차세대 방송서비스 개발의 일환으로 관심을 모으고 있는 다시점 비디오 부호화(multi-view video coding, MVC) 방식은 인접한 여러 대의 카메라로 동시에 획득한 영상을 효과적으로 압축하는데 그 목적이 있다. 이때, 중간시전 영상을 생성하여 부호화하는 과정의 참조영상으로 이용할 수 있으며, 이를 위해서는 다시점 비디오 특성에 맞는 영상보간 방법이 필요하다. 기존에 제안되었던 영상보간법은 변위의 검색범위를 초기에 설정하여 블록정합을 이용하여 화소 단위로 변위를 측정하기 때문에 카메라 사이의 거리가 크거나 객체의 움직임이 커서 변위의 변동이 심한 영상에서는 안정적인 화질의 영상을 얻기 어렵다. 또한, 고정된 크기의 블록을 이용하여 전체 변위를 측정하므로 객체의 변위차가 큰 영역에서 변위 오류가 많이 발생한다. 본 논문에서는 이와 같은 문제를 해결하여 보다 개선된 화질의 중간시점 영상을 얻기 위한 새로운 영상보간법을 제안한다. 영역분할을 이용한 초기의 변위측정 과정에서, 처음부터 최대 변위의 범위를 설정하는 대신에 블록 단위로 대략적인 변위륵 측정한 후에, 가변 블록을 이용하여 보다 세밀한 변위를 측정한다. 이 방법은 변위차가 큰 객체의 경계 부분에서 보다 정확하게 변위를 측정 할 수 있으므로, 화소 단위로 변위를 측정할 때 이전에 추한 변위 정보를 바탕으로 각 화소별로 검색 범위를 설정한다. 적응적으로 설정된 검색 범위를 이용하여 화소 단위의 변위를 측정하면 보다 개선된 변위를 얻을 수 있다. 추가적으로, 변위측정 과정에서 발생하는 변위의 오류를 최대한 줄이기 위해 각 단계별로 미디언 필터를 이용하여 변위 오류를 수정하였다. 본 논문에서 제안한 방법으로 실험한 결과 기존의 영상보간 방법보다 화질이 약 $1{\sim}4dB$ 정도 개선되었다.필, 투명도 등을 위성원격탐사 자료와 GIS를 이용하여 공간분석을 실시하고, 공간분포도를 작성함으로써 대상해역의 해양환경을 파악하였다. 본 연구결과, 분석된 위성자료가 현장조사에 의한 검증이 이루어지지 않을 경우, 영상자료분석을 통한 표층수온 추출은 대기 중의 수증기와 에어로졸에 의한 계산치의 오차가 반영되기 때문에 실측치 보다 낮게 평가 될 수 있으므로, 반드시 이에 대한 검증이 필요함을 알 수 있었다. 현지관측에 비해 막대한 비용과 시간을 절약할 수 있는 위성영상해석방법을 이용한 방법은 해양수질파악이 가능할 것으로 판단되며, GIS를 이용하여 다양하고 복잡한 자료를 데이터베이스화함으로써 가시화하고, 이를 기초로 공간분석을 실시함으로써 환경요소별 공간분포에 대한 파악을 통해 수치모형실험을 이용한 각종 환경영향의 평가 및 예측을 위한 기초자료로 이용이 가능할 것으로 사료된다.염총량관리 기본계획 시 구축된 모형 매개변수를 바탕으로 분석을 수행하였다. 일차오차분석을 이용하여 수리매개변수와 수질매개변수의 수질항목별 상대적 기여도를 파악해 본 결과, 수리매개변수는 DO, BOD, 유기질소, 유기인 모든 항목에 일정 정도의 상대적 기여도를 가지고 있는 것을 알 수 있었다. 이로부터 수질 모형의 적용 시 수리 매개변수 또한 수질 매개변수의 추정 시와 같이 보다 세심한 주의를 기울여 추정할 필요가 있을 것으로 판단된다.변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을 발견하였다. 이상의 행태적 측면과 투자성과측면의 실증결과를 통하여 한국주식시장에 있어서 시장수익률을 평균적으로 초과할 수 있는 거래전략은

• Journal of Advanced Navigation Technology
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• v.27 no.4
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• pp.396-409
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• 2023

In the field of autonomous vehicles, where high accuracy and reliability are critical, various satellite navigation augmentation systems have been developed to improve system performance. These systems generate correction and integrity information based on measurements and navigation data collected from ground reference stations, enhancing user positioning accuracy. Thus, the performance of the system heavily relies on the deployment and spacing of reference stations. To construct an effective satellite navigation augmentation system, careful consideration must be given to the installation points of reference stations. This paper presents a user positioning performance modeling formula and proposes a method for selecting the installation points of new reference stations. The proposed method involves selecting a candidate group area that can optimize the user's positioning performance. By utilizing this method, the system's performance can be improved, ensuring high accuracy and reliability for autonomous vehicle applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.426-435
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• 2013

In this paper, we propose the MIMO circular polarization feed network to enhance the communication performances from the previous $2{\times}2$ MIMO channel to $4{\times}4$ channel for Land Mobile Satellite communication system. The only possibility to extend the communication channel is to use the additional satellite because of the limitation of satellite spaces to install additional antennas. For overcoming this problems, we propose the MIMO circular polarization feed network to secure the isolation characteristics without the distant antenna space. The port isolation characteristics and each port impedance matching conditions are numerically verified and we suggest the $4{\times}4$ MIMO channel model of the proposed system and the performances are verified. The fabricated circular polarization patch antennas with the proposed feed network are measured in the reverberation chamber and 7~10 dB of diversity gain and 80 % increasement of channel capacity are obtained.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.2
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• pp.155-159
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• 1999

The mini-weather buoy using newly developed Weather Observation Through Ambient Noise (WOTAN) technology is developed. The buoy uses the cellular phone system for communication between the mini-weather buoy and the receiving station. The developed mini-weather buoy was deployed near Kijang and the comparison with land observation station was good: the rms error for wind speed estimation from underwater ambient noise was about 1 m/s. The only shortcoming of developed mini-weather buoy is that the buoy must be within the range of the cellular phone system, but it can be easily solved when satellite phone system is available.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.41-47
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• 2007

The first geostationary satellite made by Korea, COMS, has the three different payload ; Meteorological sensor, Oceanographic sensor and Ka-band communication payload. There are Meteorological & Ocean Data Communication Subsystem(MODCS) and Telemetry, Command and Ranging Subsystem(TC&R) as other RF radiation sources. MODCS transmits and receives Meteo and Ocean measurement data from/to earth using L-band and TC&R using S-band. The Ka-band communication payload will provide high-speed multimedia services and communication services for natural disaster such as prediction, prevention, and recovery services in the government communications network.Ka-band beacon is for the earth antenna pointing and the experiment of rain fading. This paper gives the analysis results about the mutual radiation effect on Ka-band communication payload, Ka-band beacon, MODCS and TC&R. Up/Down link power and coupling factor including the geometrical position and distance of antenna, filter rejection and degradation factor due to the different polarization are considered. The results show MODCS and TC&R are compatible for Ka-band communication payload and Ka-band beacon does not interfere with MODCS and TC&R normal operation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.210-212
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• 2019

위성항법시스템의 취약성에 따른 보완 시스템의 필요가 높아지면서, eLoran 시스템이 가장 현실적인 대안으로 인정받고 있다. 우리나라도 서해 일부 지역에서 eLoran 시스템의 테스트베드 구축 사업을 진행 중에 있다. 전 해양지역에 안정적인 서비스를 제공하기 위해서는 추가적인 송신국 설치가 필요하지만. 여러가지 현실적인 이유로 인해 추진되기 어렵다. 이런 문제를 해결하기 위해 기존의 NDGNSS 기준국을 활용한 측위기술이 개발되고 있다. 이미 운영 중인 NDGNSS 기준국을 활용하면 전 해상에서 탄력적 항법시스템 운용이 가능해질 수 있다. 본 논문에서는 eLoran 시스템과 NDGNSS의 기준국을 활용한 지상파 통합항법시스템의 성능을 예측할 수 있는 시뮬레이션 툴을 제작 하였다. ITU에서 배포한 송출 주파수와 거리에 따른 신호 세기, 대기잡음 등을 고려해 Cramer-Rao Lower Bound로 수신 신호의 측정 거리 오차를 계산하였다. 또한 한빛호가 항해하면서 수집한 DGPS 신호를 통해 실질적인 대기잡음을 추정하는 방법을 사용해 기존보다 정확한 SNR 계산이 가능해졌다. 해당 결과는 추후 진행될 지상파통합항법시스템 개발에 유용하게 활용될 것으로 기대된다.

• Journal of Space Technology and Applications
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• v.4 no.1
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• pp.48-61
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• 2024

In this paper, we introduce the concept of the cube satellite Chungnam National University Laser Unity Bus (CLUB), which can provide an integrated infrastructure for various ground-space laser applications. With the advent of the new space era, the rapid expansion of space utilization has begun to reveal the limitations of conventional radio frequencies. As space missions diversify, lasers are garnering attention as a viable alternative. Between ground and space, lasers are applied in various fields including satellite laser ranging (SLR), laser weapons, and laser communication. However, laser used between the ground and space are significantly influenced by the Earth's atmosphere. Consequently, understanding the atmospheric effects on laser propagation is crucial. In particular, atmospheric turbulence, which refracts and distorts laser beams, intensifies closer to the Earth's surface, exerting a greater impact on the uplink than on the downlink. While downlink verification is facilitated by ground detection, verifying the uplink poses challenges due to the necessity of space-based detection. In response to these challenges, we propose the idea of cube satellite as a means to enhance understanding and verification of laser propagation in the uplink. Additionally, we present the results of conceptual design by analyzing requirements, focusing on mission design of the CLUB cube satellite, following the stages of systems engineering for systematic cube satellite development.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.609-617
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• 2016

In general, Personal Navigation Systems (PNSs) can be defined systems to acquire pedestrian positional information. GPS is an example of PNS. However, GPS can only be used where the GPS signal can be received. Pedestrian Dead Reckoning (PDR) can estimate the positional information of pedestrians using Inertial Measurement Unit (IMU). Therefore, PDR can be used for GPS-disabled areas. This paper proposes a PDR scheme considering various movement types over GPS-disabled areas as combat environments. We propose a movement distance estimation scheme and movement direction estimation scheme as pedestrian's various movement types such as walking, running and crawling using IMU. Also, we propose a fusion algorithm between GPS and PDR to mitigate the lack of accuracy of positional information at the entrance to the building. The proposed algorithm has been tested in a real test bed. In the experimental results, the proposed algorithms exhibited an average position error distance of 5.64m and position error rate in goal point of 3.41% as a pedestrian traveled 0.6km.