• Journal of Navigation and Port Research
• /
• v.38 no.3
• /
• pp.227-232
• /
• 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
• /
• 2017.11a
• /
• pp.199-200
• /
• 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.

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

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2018.11a
• /
• pp.95-96
• /
• 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 Navigation and Port Research
• /
• v.37 no.1
• /
• pp.35-40
• /
• 2013

In the eLoran navigation system, the dominant deterioration factors of navigation accuracy are the TOA measurement errors on user receiver and the GDOP between the receiver and the transmitters. But if the ASF data measured at dLoran reference station are provided for users through the Loran data channel, it will be possible to correct the TOA measurement errors. The position accuracy can be determined by the DOP depending on the geometry of receiver-transmitters, and their optimal placement improves the navigation accuracy. In this study we determined the geometric placement in case of up to six stations, and evaluated the performance of position accuracy for the receiver-transmitter geometry set of eLoran stations. The proposed geometry of eLoran stations can be referred for the construction of eLoran infrastructure meeting the capability of HEA for maritime, and time/frequency users in Korea.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2017.11a
• /
• pp.193-195
• /
• 2017

This paper focuses on development status of eLoran system which is an representative backup PNT system in order to overcome the vulnerability of GNSS signals by radio frequency interference such as jamming. eLoran testbed system consists of new transmitting system for amplifying the signal through signal generation and modulation, differential Loran (dLoran) reference stations for calculating the signal errors received from transmitters, an integrated operation and control system (IOCS) for eLoran service. Therefore we present the configuration of testbed architecture for trial operation of eLoran service and the development status, and discuss about the next step toward backup PNT service using eLoran system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.12
• /
• pp.1053-1058
• /
• 2016

The eLoran(enhanced Long Range Navigation) transmitting antenna is analyzed for co-location with an AM transmitting antenna in an MF transmitting site. To compensate for the loading effect, the umbrella-type loading is applied for eLoran antenna. The validity of the co-location between the MF antenna and the eLoran antenna is verified through the simulation results of the radiation pattern and the return loss. Also, coupling including antenna matching circuit is analyzed to verify the effect of the transmitting circuit. The coupling between the LF and eLoran antenna is -53.3 dB at 100 kHz and -64.8 dB at 1,053 kHz, respectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2013.10a
• /
• pp.372-373
• /
• 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 Positioning, Navigation, and Timing
• /
• v.2 no.2
• /
• pp.109-114
• /
• 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
• /
• v.40 no.6
• /
• pp.385-390
• /
• 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.