• Journal of Navigation and Port Research
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• v.35 no.8
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• pp.619-624
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• 2011

A significant factor limiting the ranging accuracy of Loran (Long Range Navigation) signal is the additional secondary factor (ASF) in the time of arrival (TOA) measurements. Precise ASF values are essential if Loran deliver the high absolute accuracies demanded for aircraft approach, maritime harbour entrance. We measured the absolute propagation delay between Pohang Loran signal and Loran receiver output signal by comparing with Cesium atomic clock. In this study we measured ASFs between Pohang 9930M station and the 12 measurement points in the Yeongil Bay by using the measurement technique of absolute time delay. The measurement points were spaced at interval of 3 km by 3 km. An E-field antenna and an H-field antenna were used to improve the accuracy of ASF measurements and a DGPS (Differential GPS) receiver was used for accurate positions. We have gotten the result that the measured ASFs were compared with the predicted ASFs through this measurement technique.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.77-80
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• 2019

GPS 항법 시스템은 재밍(jamming)에 취약한 것으로 알려져 있다. 실제로 2010년부터 북한은 서해상과 수도권에 GPS 전파교란 공격을 감행, 운행 중이던 선박과 항공기의 네비게이션 등에 다수의 장애현상을 유발시켰다. 이것에 대한 대안으로 eLoran(enhanced Long Range Navigation)이 GPS 항법 시스템을 보완할 수 있다고 알려져 있다. 이에 따라 해양수산부(MOF)는 기존 포항·광주 로란-C 송신국에 UTC(Coordinated Universal Time) 기반의 시각동기시스템 구축하여 지상파 eLoran 시스템으로 활용하기 위한 eLoran 사업을 진행하고 있다. 본 논문에서는 기존 포항·광주 로란-C 송신국에 UTC(Coordinated Universal Time) 기반의 시각동기시스템을 구축하기 위한 요구 사항을 살펴보고, 이 요구 사항에 따른 포항·광주 로란-C 시각동기시스템의 구축 결과에 대해 기술하였다.

• Journal of information and communication convergence engineering
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• v.5 no.4
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• pp.295-299
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• 2007

This paper presents the ASF(Additional Secondary Factor) modeling of DGPS beacon signal. In addition to DGPS's original purpose, the feasibility to utilize DGPS system for timing and navigation has been studied. For timing and navigation, the positioning system must know the accurate time delay of signal traveling from the transmitter to receiver. Then the delay can be used to compute the user position. The DGPS beacon signal transmits the data using medium frequency, which travels through the surface and cause the additional delay rather than the speed of light according to conductivities and elevations of the irregular terrain. We introduce the modeling of additional delay(ASF) and present the results of implementation. The similar approach is Locan-C. Loran-C has been widely used as the maritime location system and was enhanced to E-Loran(Enhanced Loran). E-Loran system uses the ASF estimation method and is able to provide the more precise location service. However there was rarely research on this area in Korea. Hence, we introduce the ASF and its estimation model. With the comparison of the same condition and data from the original Monteath model and ASF estimation data of Loran system respectively, we guarantee that the implementation is absolutely perfect. For further works, we're going to apply the ASF estimation model to Korean DGPS beacon system with the Korean terrain data.

• Journal of the Korea Society of Computer and Information
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• v.14 no.2
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• pp.111-118
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• 2009

Against Anomaly of GPS, there are several projects of independent satellite navigation systems like Galileo of Europe and QZSS of Japan and modernization of terrestrial navigation system like Loran. In domestic, the need of independent navigation system was proposed and DGPS signal was nominated as the possible substitute. The DGPS signal uses medium frequency, which travels through the surface and cause the additional delay rather than the speed of light according to Conductivities and elevations of the irregular terrain. The similar approach is Locan-C. Loran-C has been widely used as the maritime location system. Loran-C uses the ASF estimation method and provides more precise positioning. However there was rarely research on this area in Korea Therefore, we introduce the legacy guaranteed model of additional delay(ASF) and present the results of implementation. With the comparison of the original Monteath results and BALOR results respectively, we guarantee that the implementation is absolutely perfect. For further works, we're going to apply the ASF estimation model to Korean DGPS system with the Korean terrain data.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.3-4
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• 2018

과거 3-4년 전까지 위성전파항법시스템의 백업 시스템으로 유일하게 논의되고 있었던 현실적 대안은 eLoran이었다. eLoran은 기존에 활용성이 낮아져 서비스가 점차 중단되고 있는 로란-C 시설을 개선하여 보다 높은 PNT 성능을 제공하도록 고안되었다. 기존에 로란-C 시설이 있는 국가나 지역에서는 위성전파항법시스템의 백업 시스템으로 eLoran을 효과적으로 확보할 수 있는 것이다. 그러나 기존 로란-C 시설을 이미 철거하였거나, 로란-C 시설을 가지고 있지 않았던 국가 입장에서는 eLoran을 확보하기 위해 로란-C 시설을 보유한 국가보다 더 많은 시설구축 비용이 필요하게 된다. 반면에 R-Mode는 현재 해상에서 활용되고 있는 전파신호를 이용하므로 신규 전파항법 인프라 구축에 따른 큰 투자 없이 적은 비용으로 위성전파항법시스템의 백업 시스템을 구현할 수 있다는 장점을 갖는다. 대한민국은 세계에서 유일하게 국가안보적 측면에서 GPS 전파간섭의 위협을 받고 있는 국가이다. 대한민국이 직면한 GPS 전파간섭은 해외에서 보고되고 있는 좁은 지역에서의 개인적 소규모 전파간섭과는 차원이 다르다. 특히 지난 2016년 3월 말, 우리나라는 약 엿새간 수도권과 강원지역 등이 동시에 GPS 전파간섭의 영향권 안에 든 바 있다. 이때 GPS 전파간섭은 과거에 발생한 GPS 전파간섭보다 더 넓은 지역에 영향을 주었고, 어선과 같은 소규모 선박의 조업까지 방해하는 피해를 안겼다. 본 논문은 대한민국이 하루 속히 해결해야 할 현안으로 인식되고 있는 위성전파항법시스템의 백업 시스템으로 중파 비컨 R-Mode를 적용할 필요가 있는지 논하고자 한다.

• 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.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.349-352
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• 2013

최근 태양흑점 폭발로 인해 지구자기장이 교란되어 통신장애가 발생하는 등 GNSS을 이용하는 산업 기반에 크고 작은 피해사례가 증가하고 있다. 2012년 3월과 2013년 6월 중에 태양흑점 폭발로 우주전파경보 발령(3단계"주의) 됨에 따라 해양수산부 위성항법 중앙사무소에서 운영하고 있는 위성항법보정시스템(DGPS)과 지상 전파항법시스템(Loran-C) 데이타를 분석하였다. 비의도적인 전파 교란 등으로 인한 GNSS 취약성 대비 대체 항법 효율성 확보 방안에 대한 eLoran으로 지상 항법시스템 인프라 구축 필요성을 제안하였다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.22 no.4
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• pp.83-89
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• 1986

A series of observations was conducted in order to study the accuracy of the Jlosition by automatic Loran-C navigation system with two Loran-C chains, namely 5970 and 9970 Chain, in the EJst Sea and Southern Sea of the Korean Peninsular from July to September 1986. Diurnal variation of positional error measured by 5970 Chain was almost stable throughout a whole day, and it was fairly stabl2 in the daytime but fluctuated more or less by night at each station by 9970 Chain. Daily mean values of positional error by 5970 Chain were 6'.44 SWat U1reungdo, 0'.22 SE at Jugbyeon, 0'.91 NE at Guryongpo, 0'.37 SE at Pusan, 0'.30 SE at Yokchi, 0'.37 NW at Cheju and 12'.51 SE at Taeheuksan. By 9970 Chain, they Wer2 0'.27 SWat Ulreungdo, 0'.27 SE at Jugbyeon, 0'.09 SWat Guryongpo, 0'.19 SE at Pusan, 0'. IG SE at Yokchi, 0'.17 Sr:: at Cheju and 0'.52 SE at Taeheuksan.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.310-311
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• 2011

In this paper, refer to necessity about independent navigation system for back up of GPS by LORAN-C and suggest a solution of Co-location modeling of LORAN-C with DGPS and analysing for the interference.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.2
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• pp.112-121
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• 1984

This paper is compared the simulation tables by the general propagation velocity and the calculated propagation velocities with distances and times to take to be transmitted Loran C wave from master station to slave stations, with Loran C tables, and compared the accuracy of position fixes by the simulation to them by Loran C table with the time differences of 9970 chain to be measured in the south coast of Korea, and by the simulation with the time differences of 5970 chain to be measured at definite position to them. The results obtained are as follows; 1. the simulation tables by the calculated propagation velocities is nearer to Loran C tables than it by the general propagation velocity. 2. The ranges of total errors of the simulation positions by the general propagation velocity and the calculated propagation velocities to the position fixies of Loran C table with the time differences of 9970 chain to be measured in the south coast of Korea are 0.2-0.7 miles, 0.01-0.1 miles, and the mean values of them are 0.46 miles and standard deviations of time are 0.1 miles, 0.03 miles respectively. 3. Mean value of total errors of the simulation position by the calculated propagation velocities to the definite position with the time difference of 5970 chain is 0.2miles and is reduced 0.1-0.2 miles than it by the general propagation velocity.