• Journal of Navigation and Port Research
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• v.34 no.3
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• pp.175-180
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• 2010

In the almost application parts, GNSS being used the primary navigation system on world-widely. However, some of nations attempt or deliberate to enhance current Loran system, as a backup to satellite navigation system because of the vulnerability to the disturbance signal. Loran interests in supplemental navigation system by the development and enhancement, which is called eLoran, and that consists of advancement of receiver and transmitter and of differential Loran in order to increase the accuracy of current Loran-C. A significant factor limiting the ranging accuracy of the eLoran signal is the ASF in the TOAs observed by the receiver. The ASF is mostly due to the fact that the ground-wave signal is likely to propagate over paths of varying conductivity and topography. This paper presents comparison results between the predicted ASF and the measured ASF in a southern east region of Korea. For predicting ASF, the Monteath model is used. Actual ASF is measured from the legacy Loran signal transmitted Pohang station in the GRI 9930 chain. The test results showed the repeatability of the measured ASF and the consistent characteristics between the predicted and the measured ASF values.

• Journal of Navigation and Port Research
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• v.36 no.6
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• pp.475-480
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• 2012

In order to establish eLoran (enhanced Long Range Navigation) system, it needs the advancement of receiver, transmitter, data channel addition for Loran information, differential Loran sites for compensating Loran-c signal and ASFs (Additional Secondary Factors) database, etc. In addition, the precise synchronization of transmitting station to the UTC (Coordinated Universal Time) is essential if Loran delivers the high absolute accuracy of navigation demanded for maritime harbor entrance. For better timing synchronization to the UTC among transmitting stations, it is necessary to measure and monitor the transmission delay of the station, and the correction information of the transmitting station should be provided to the user's receivers. In this paper we presented the measurement method of absolute delay of Pohang Loran transmitting station and developed a time delay measurement system and a phase monitoring system for Loran station. We achieved -2.23 us as a result of the absolute phase delay of Pohang station and the drift of Loran pulse of the station was measured about 0.3 us for a month period. Therefore it is necessary to measure the delay offset of transmitting station and to compensate the drift of the Loran signal for the high accuracy application of PNT (Positioning, Navigation and Timing).

• Journal of Navigation and Port Research
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• v.36 no.8
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• pp.625-630
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• 2012

The DGNSS Central Office operates 17 DGNSS reference stations. Compared to the other DGNSS sites, the TEQC data quality of some sites is poorer. In this study, we tried to find out the causes that degrade the quality of GPS data for the purpose of improving the signal quality of the DGNSS stations. We selected the Chungju station that is the one of those stations with bad data quality. Through the on-site visit, we found that there is no signal-blocking obstacles. In addition to site surveys, we conducted two experiments; simultaneous observation considering environmental factors and comparison test through equipment replacements to check the malfunctioning of GPS equipments. In the simultaneous test results, we realized that environmental factors do not induce any bad effects on the data quality. In equipment replacement experiments, we confirmed that the data quality is of excellent quality when the test receiver was used instead of the original one installed at the site. When we replaced the antenna instead of the receiver, the data quality was bad. Through those two experiments, we concluded that the receiver is the main factor that degrades the signal quality.

• Journal of Navigation and Port Research
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• v.40 no.6
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• pp.385-390
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• 2016

ELoran Systems can provide Position, Navigation, and Time services with comparable performance to Global Positioning Systems (GPS) as a back up or alternative system. High timing and navigation performance can be achieved by eLoran signals because eLoran receivers use "all-in-view" reception. This incorporates Time of Arrival (TOA) signals from all stations in the service range because each eLoran station is synchronized to Coordinated Universal Time (UTC). Transmission station information and the differential Loran correction data are transmitted via an additional Loran Data Channel (LDC) on the transmitted eLoran signal such that eLoran provides improved Position Navigation and Timing (PNT) over legacy Loran. In this paper, we propose a technique for adapting the delay time compensation values in eLoran timing receivers to provide precise time comparison. For this purpose, we have designed a system that measures time delay from the crossing point of the third cycle extracted from the current transformer at the end point of the transmitter. The receiver delay was measured by connecting an active H-field, an E-field and a passive loop antenna to a commercial eLoran timing receiver. The common-view time transfer technique using the calibrated eLoran timing receiver improved the eLoran transfer time. A eLoran timing receiver calibrated by this method can be utilized in the field for precise time comparison as a GNSS backup.

• Journal of Navigation and Port Research
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• v.33 no.10
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• pp.691-697
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• 2009

Hardware dedicated off-the-shelf maritime differential GPS RSIM lacks the open architecture to meet all the minimum maritime user requirements and to include future GNSS improvements after recapitalization. This paper carries out a study to replace existing hardware dedicated differential GPS RSIM with software differential GPS RSIM in order to make up the weak point of hardware dedicated off-the-shelf maritime differential GPS RSIM. In this paper, the architecture of software RSIM is proposed for maritime DGPS recapitalization. And the feasibility analysis of the proposed software differential GPS RSIM is performed as the first phase to realize the proposed architecture. For the feasibility analysis, the prototype RF module and DSP module are implemented with properties as wide RF bandwidth, high sampling frequency, and high speed transmission interface. This paper shows that the proposed architecture has the possibility of real time operation of software RSIM functionality onto the PC-based platform through the analysis of computation time. Finally, this paper verifies that the L1/L2 dual frequency software differential RSIM designed according to the proposed method satisfies the performance specifications set out in RTCM paper 221-2006-SC104-STD.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.608-611
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• 2006

COSPAS-SARSAT 시스템은 위성체와 지상 설비를 이용하여 항공기 또는 선박 등이 조난 시에 탐색구조(SAR: Search and Rescue) 활동을 도울 수 있도록 조난경보와 위치정보를 제공하는 시스템이다. COSPAS-SARSAT 서비스의 경우, 조난신호 접수에서 조난위치확정까지 평균 1시간 이상이 소요되고, 위치정확도가 수 Km 정도로 범위가 넓은 편이다. 이러한 문제점을 개선하기 위해서 중궤도 위성을 이용한 차세대 탐색구조 시스템 개발이 추진 중에 있으며 EU에서 2011년 FOC(Full Operation Capability)를 목표로 개발중인 갈릴레오 항법위성 프로젝트의 경우 SAR 중계기를 탑재하여 탐색구조 서비스를 제공할 계획에 있다. 갈릴레오 탐색구조(SAR/Galileo) 서비스는 수 m급의 위치정확도, 10분 이내의 조난신호 접수에서 구조까지 소요시간, 및 조난자에게 회신링크 서비스 제공 등 보다 향상된 탐색구조 성능을 제공하기 위해 개발 중에 있으므로, 갈릴레오 위성 서비스가 시작되면 탐색구조시스템 체계에 보다 신속하고 정확한 구조가 가능할 것으로 예상된다. 우리나라에서는 COSPAS-SARSAT 회원국으로 가입하여 현재 송도 해양경찰청 내에 LEOLUT와 MCC가 설치되어 운용되고 있다. 날로 더해가는 다양한 재난에 대한 인명구조를 신속하고 효과적으로 대처하기 위해 차세대 갈릴레오 탐색구조 지상국 도입이 절실하다고 할 수 있다. 따라서, 탐색구조 단말기를 포함한 지상국 인프라의 구축 등 갈릴레오 탐색구조 지상시스템 개발의 참여 방안에 관한 연구는 매우 시기적절하고 중요한 연구이다. 본 논문은 갈릴레오 사업에 참여하여 SAR/Galileo 개발을 주관하고 있는 중국의 사례를 분석함으로 우리나라가 차세대 갈릴레오 탐색구조 지상시스템 개발에 참여하기 위해서 필요한 참여방법 및 절차 등을 도출하고, 참여 가능한 개발범위, 참여전략 및 추진체계에 대해서 제안한다.법의 성능을 평가를 위하여 원본 여권에서 얼굴 부분을 위조한 여권과 기울어진 여권 영상을 대상으로 실험한 결과, 제안된 방법이 여권의 코드 인식 및 얼굴 인증에 있어서 우수한 성능이 있음을 확인하였다.진행하고 있다.태도와 유아의 창의성간에는 상관이 없는 것으로 나타났고, 일반 유아의 아버지 양육태도와 유아의 창의성간의 상관에서는 아버지 양육태도의 성취-비성취 요인에서와 창의성제목의 추상성요인에서 상관이 있는 것으로 나타났다. 따라서 창의성이 높은 아동의 아버지의 양육태도는 일반 유아의 아버지와 보다 더 애정적이며 자율성이 높지만 창의성이 높은 아동의 집단내에서 창의성에 특별한 영향을 더 미치는 아버지의 양육방식은 발견되지 않았다. 반면 일반 유아의 경우 아버지의 성취지향성이 낮을 때 자녀의 창의성을 향상시킬 수 있는 것으로 나타났다. 이상에서 자녀의 창의성을 향상시키는 중요한 양육차원은 애정성이나 비성취지향성으로 나타나고 있어 정서적인 측면의 지원인 것으로 밝혀졌다.징에서 나타나는 AD-SR맥락의 반성적 탐구가 자주 나타났다. 반성적 탐구 척도 두 그룹을 비교 했을 때 CON 상호작용의 특징이 낮게 나타나는 N그룹이 양적으로 그리고 내용적으로 더 의미 있는 반성적 탐구를 했다용을 지원하는 홈페이지를 만들어 자료 제공 사이트에 대한 메타 자료를 데이터베이스화했으며 이를 통해 학생들이 원하는 실시간 자료를 검색하여 찾을 수 있고 홈페이지를 방분했을 때 이해하기 어려운 그래프나 각 홈페이지가 제공하는 자료들에 대한 처리 방법을 도움말로 제공받을 수 있게 했다. 실시간 자료들을 이용한 학습은 학생들의 학습 의욕과 탐구 능력을 향상시켰으며 컴퓨터 활용 능력과 외국어 자료 활용 능력을 향상 시키는데도 도움을 주었다.지역산업 발전을 위한 기술역량이 강화될 것이다.정 ${\rightarrow}$ 분배 ${\rightarrow}$ 최대다수의 최대행복이다.는 역할을 한다. 따라

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.491-499
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• 2011

Starting with maritime DGPS base stations of Palmido, Ochongdo which have been operated since 1999, truly our nation has become the most powerful country possessed with total of 17 DGNSS base stations in the field of DGNSS operation infrastructure. This paper examines into the country's DGNSS services as measuring the service range of the maritime DGPS base stations in the domestic ferry lines which sections are from Jeju to Incheon, from Busan to Jeju, from Jeju to Nokdong, the propagation characteristics of the radio waves of 300 kHz bands on sea and land path. As a result of identifying the service range of the DGPS in the sea routes of the southern sea and the western sea, the measured results of the DGPS signals are confirmed more than 100 NM(recommended service range). It can be possible to practical use the position information, which is safe navigation and various marine traffic management systems. It will be useful an expansion of maritime DGPS reference station in the near future.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.9
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• pp.781-788
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• 2016

In this paper, a real-time on-board orbit determination algorithm using the high precise orbit propagator is suggested and its performance is analyzed. Orbit determination algorithm is designed with the Extended Kalman Filter. And it utilizes the orbit calculated from the Pseudo-range as observed data. The performance of the on-board orbit determination method implemented in the GPS-12 receiver is demonstrated using the GNSS simulator. Orbit determination performance using high precise orbit propagator was analyzed in comparison to the orbit determination result using $J_2$ orbit propagator. The analysis result showed that position and velocity error are improved from 43.61 m($3{\sigma}$) to 23.86 m($3{\sigma}$) and from 0.159 m/s($3{\sigma}$) to 0.044 m/s($3{\sigma}$) respectively.