• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2017.11a
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• pp.199-200
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• 2017

In order to meet the international performance requirements for eLoran testbed operation, it is necessary to measure ASF (Additional Secondary Factor) of vessel's route as well as differential correction and the provision using differential Loran (dLoran) station operation. According to HEA (Harbor Entrance and Approach) performance of the IMO, the position accuracy should be within 10meters. Therefore this paper presents the possibility to meet the position accuracy of the IMO HEA through simulation results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.73-74
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• 2019

We are developing a receiver that integrates eLoran and GNSS for navigation. The receiver shows similar performance to LORADD receiver in single navigation using Loran-C. In the case of GNSS navigation, the receiver uses GPS and GLONASS or GPS and BDS, so it has better navigation performance than the LORADD receiver using only GPS. Therefore, it is possible to expect better performance than the LORADD receiver in the integrated navigation which can complete the time synchronization between the chains later and obtaion the TOA. Loran data channel decoding function is implemented for eLoran navigation and the function of eliminating error factors such as interference is being implemented.

• 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).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.163-168
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• 2005

Loran-C(Long Range Navigation) is the only stand alone navigation system of the world Ministry of Maritime Affairs and Fisheries(MOMAF} of Korea is operating the Korea Chain(GRI : 9930, Master station : Pohang, slave station : Kwangju, Gessashi; Nijima, Ussurisk) around the country. Due to decreasing the users and being antiquated New Loran System is being developed in United States. In this study, the policy establishment of Loran-C in Korea is suggested.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2017.11a
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• pp.97-99
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• 2017

본 논문에서는 eLoran 수신기 및 GPS 수신기를 통해 출력되는 NMEA 디지털 데이터를 이용해 GPS 값의 변화를 실시간으로 감시하고, GPS 위치정보의 이상 발생 시 eLoran의 위치정보로 자동 스위칭하여 재밍이나 스푸핑 등의 GPS 전파교란에 대비할 수 있는 장치의 개발에 관하여 연구하였다.

• Journal of Positioning, Navigation, and Timing
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• v.2 no.2
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• pp.109-114
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• 2013

The vulnerability of GPS to interference signals was reported in the early 2000s, and an eLORAN system has been suggested as a backup navigation system for replacing the existing GPS. Thus, relevant studies have been carried out in the United States, Europe, Korea, etc., and especially, in Korea, the research and development is being conducted for the FOC of the eLORAN system by 2018. The required performance of the eLORAN system is to meet the HEA performance, and to achieve this, it is essential to perform ASF correction based on a dLORAN system. ASF can be divided into temporal ASF, nominal ASF, and spatial ASF. Spatial ASF is the variation due to spatial characteristics, and is stored in an eLORAN receiver in the form of a premeasured map. Temporal ASF is the variations due to temporal characteristics, and are transmitted from a dLORAN site to a receiver via LDC. Unlike nominal ASF that is obtained by long-term measurement (over 1 year), temporal ASF changes in a short period of time, and ideally, real-time correction needs to be performed. However, it is difficult to perform real-time correction due to the limit of the transmission rate of the LDC for transmitting correction values. In this paper, to determine temporal ASF correction frequency that shows satisfactory performance within the range of the limit of data transmission rates, relative variations of temporal ASF in summer and winter were measured, and the stability of correction values was analyzed using the average of temporal ASF for a certain period.

• 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.37 no.4
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• pp.375-381
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• 2013

In order to establish eLoran system it needs the betterment of a receiver and a transmitter, the add of data channel to loran pulse for loran system information and the differential Loran for compensating Loran-c signal. Precise ASF database map is essential if the Loran delivers the high absolute accuracy of navigation demanded at maritime harbor entrance. In this study we developed the ASF mapping method using predicted ASFs compensated by the measured ASFs for maritime in the harbor. Actual ASF is measured by the legacy Loran signal transmitted from Pohang station in the GRI 9930 chain. We measured absolute propagation delay between the Pohang transmitting station and the measurement points by comparing with the cesium clock for the calculation of the ASFs. Monteath model was used for the irregular terrain along the propagation path in the Yeongil Bay. We measured the actual ASFs at the 12 measurement points over the Yeongil Bay. In our ASF-mapping method we estimated that the each offsets between the predicted and the measured ASFs at the 12 spaced points in the Yeongil. We obtained the ASF map by adjusting the predicted ASF results to fit the measured ASFs over Yeungil bay.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.10a
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• pp.362-364
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• 2012

e_Loran은 GNSS와는 다르지만 상호 보완적이고 통신네트워크 및 전력그리드등과 같은 중요한 국가 인프라에 GPS를 대신해서 시각과 주파수 신호를 제공할 수 있다. 그리고 현재 추진 중에 있는 e_Loran 시스템 구축이 완료되면 시각과 주파수 부분에서 예비 신호원으로서 활용이 가능할 것이다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.10a
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• pp.283-285
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• 2014

우리부에서는 최근 북한의 의도적인 GPS 전파교란이 지속적으로 증가하고 있으나, 전파 교란에 대응할 수 있는 대체 시스템이 부재하여 사회적 혼란이 우려됨에 따라, GPS 전파교란 대응 대체항법시스템으로 eLoran 시스템 구축을 국정과제로 추진 중에 있다.