• Journal of Navigation and Port Research
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• v.38 no.3
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• pp.227-232
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• 2014

There are three essential components of eLoran: dLoran, data map of ASF, and the Loran data channel. Particularly, dLoran improves navigation accuracy, which is the core technology of eLoran systems. The requirement of HEA's absolute accuracy, less than 20 meters, can be satisfied via dLoran measurements and their corrections. In this study, dLoran measurements using the Pohang Loran-C (9930M) station signal were conducted at Yeongil Bay. We established a dLoran reference station at Homigot Management Office for navigation aids within the Bay. We estimated the effectiveness of the dLoran between the reference site (Homigot Management Office) and a test site (Heunghwan beach) by measuring TOAs. We verified that the TOA data measured at these two regions were highly correlated. The temporal differences in the data between the dLoran reference station and test site were about 10~30 ns per day, which is equivalent to a ranging error of 3~9 m. This result shows that eLoran can meet the requirement of 8~20 meters position accuracy for maritime HEA by correcting the ASF at the user's receiver.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.71-72
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• 2019

In this study, we describe a method of measuring position using the Additional Secondary Factor (ASF) compensation technique of the eLoran concept in the situation where only Loran-C signals are received without eLoran time broadcasting. Next, we describe the result of test performed to verify the method. The test results showed the position accuracy within 20m and we found the possibility of the method. The method is expected to be used to verify user positioning accuracy before improving Loran-C to eLoran.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.95-96
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• 2018

This paper deals with the development status of eLoran system which is the best backup position, navigation, and timing (P NT) system of Global Navigation Satellite System (GNSS) and its performance result. I t especially explains the status of eLoran testbed implementation for the eLoran test service, development of eLoran transmitting system, differential Loran (dLoran) system, integrated operation and control system (IOCS), and integrated eLoran/GNSS receiver. The paper discusses about the future plan for the build up test transmitting station and backup P NT service to succeed to the trial operation of eLoran testbed system.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.2
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• pp.107-112
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• 2011

Several developed countries have been developing their own satellite navigation systems, such as Europe's Galileo, China's BEIDOU, and Japan's QZSS, to cope with clock errors and signal vulnerabilities of GPS. In addition, modernization of Loran, eLoran, for GPS backup has been conducted. In Korea, a dependent navigation system has been required and for GPS backup, the need for utilization of time synchronization infrastructure through the modernization of Loran has been raised. Loran signal uses 100Khz groundwave. A significant factor limiting the ranging accuracy of the Loran signal is the ASF arising from the fact that the groundwave signal is likely to propagate over paths of varying conductivity and topography. Thus, an ASF compensation method is very important for Loran and eLoran navigation. This paper introduces the propagation delay model and then compares and analyzes the estimations from the propagation delay model and measured ASFs.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.2
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• pp.188-193
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• 2010

With GPS being the primary navigation system, Loran use is in steep decline. However, according to the final report of vulnerability assessment of the transportation infrastructure relying on the global positioning system prepared by the John A. Volpe National Transportation Systems Center, there are current attempts to enhance and re-popularize Loran as a GPS backup system through the characteristic of the ground based low frequency navigation system. To advance the Loran system such as Loran-C modernization and eLoran development, research is definitely needed in the field of Loran-C receiver signal processing as well as Loran-C signal design and the technology of a receiver. We have developed a set of Matlab tools, which implement a software Loran-C receiver that performs the receiver's position determination through the following procedure. The procedure consists of receiving the Loran-C signal, cycle selection, calculation of the TDOA and range, and receiver's position determination through the Least Square Method. We experiences the effect of an incorrect cycle selection and various error factors (ECD, ASF, sky wave, CRI, etc.) from the result of the Loran-C signal processing. It is apparent that researches which focus on the elimination and mitigation of various error factors need to be investigated on a software Loran-C receiver. These aspects will be explored in further work through the method such as PLL and Kalman filtering.

• 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.190-192
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• 2017

The manufacture of current Loran-C signal receiver has been discontinued and there are no spare parts for that. eLoran system is being developed. Judging from these facts, it is necessary to purchase eLoran receivers which also can receive Loran-C signal. Furthermore, the coverage of Loran-C has been decreased as the closure of transmitting stations in Japan. The current monitor station in Ganjeolgot, Ulsan shall be moved to a new place.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.372-373
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• 2013

위성항법시스템(GNSS)에 대한 전파교란에 대응하기 위한 보완항법시스템인 eLoran은 고출력의 지상파를 사용하기 때문에 전파교란이 현실적으로 힘들다는 장점이 있다. eLoran 신호는 세계표준시(UTC)에 동기화 되어있어서 송신 출력에 따라 실내와 같이 GNSS 신호의 수신이 힘든 경우에도 정확한 시각(timing) 정보를 제공할 수 있다. eLoran을 이용한 시각 정보 제공은 미국 국방부(DoD)에서도 최근에 많은 관심을 보이고 있다. 또한 eLoran은 자체 데이터 채널을 보유하고 있어서 eLoran 보정 신호를 전송할 수 있고, 전파기만에 대비하여 eLoran 신호인증 기법을 적용할 수 있다. 전파교란의 영향을 받지 않고 데이터를 전송할 수 있기 때문에 안정적인 데이터 전송이 필요한 각종 분야에서 eLoran 데이터 채널의 활용이 가능하다. 현재 우리나라는 GNSS를 보완하는 위치 항법 시각(PNT) 시스템으로써 2018년 정상 운용을 목표로 eLoran 시스템 구축 사업을 진행하고 있다.

• 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 the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.815-821
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• 2021

This study addresses on the design of performance monitoring system for the time synchronization service of the enhanced long-range navigation (eLoran) system, which has a representative ground-wave radio broadcast system capable of providing positioning, navigation, timing and data (PNT&D) services. The limitations of time-synchronized systems due to the signal vulnerabilities of the global navigation satellite system (GNSS) are explained, and the performance monitoring system for the eLoran timing service as a backup to the GNSS is proposed. The time synchronization service using eLoran system as well as system configurations and the user requirements in the differential Loran (dLoran) system are described to monitor the time synchronization performance. The results of the designed system are presented for long-term operation in the eLoran testbed environment. As the results of time performance monitoring, we were able to verify the time synchronization precision within 43.71 ns without corrections, 22.52 ns with corrections. Based on these results, the eLoran system can be utilized as a precise time synchronization source for GPS timing backup.