• 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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• 2015.10a
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• pp.268-269
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• 2015

National Maritime PNT Office is operating 17 DGPS reference sites. Considering the relatively small size of South Korea, however, we thought that it is maintaining too many stations. For this reason, new algorithms were developed to effectively generate Pseudo-Range Corrections for the purpose of providing consistent DGPS accuracies throughout the country even with a minimum number of stations.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.4
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• pp.187-193
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• 2015

A maritime Differential Global Positioning System (DGPS) reference station broadcasts correction information to users having a DGPS receiver so that the navigation performance can be improved. A maritime DGPS reference station consists of a reference station (RS) that generates and broadcasts correction information, an integrity monitor (IM) that monitors the integrity of correction information, and a control station (CS) that controls them. A maritime DGPS reference station is continuously operated for 24 hours, and thus improvement in the ease of operation is a major element that can improve the performance of the system. In this study, a configuration of a maritime DGPS reference station that can improve the ease of operation and a relevant protocol were proposed, and an example of the implementation of the proposed system was presented.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.808-814
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• 2021

The International Maritime Organization (IMO) explicitly stipulates the required performance of satellite based radio-navigation systems available for navigational purposes. Until 2019, the IMO had only recognized systems that could be serviced globally for satellite based radio-navigation. However, India's regional navigation satellite system has been approved recently, and other regional navigation satellite systems have also been made available for maritime navigation. Thus far, the IMO has approved the use of a total of five satellite navigation systems, such as the GPS, GLONASS, Galileo, BeiDou, and NavIC. In Korea, in addition to the four satellite based radio-navigation systems that are used excluding NavIC, Japan's regional navigation satellite system that has not yet been approved can be received. Japan has requested the IMO to recognize the QZSS as a WWRNS to formalize its use for ocean navigations. Given that the service coverage of the QZSS is not limited to Japanese territorial waters and also includes Korean waters, the suitability analysis of the QZSS for domestic navigation is important for maritime safety. This study aims to analyze the suitability of using the QZSS for domestic navigation. Accordingly, this work explores the status and plans of the QZSS as well as the performance required by the IMO for recognition as a WWRNS. The methods and environmental conditions examined in this work are described, and the analyzed results are presented in terms of positioning accuracy and availability.

• 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.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.12-20
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• 2017

A maritime DGPS in Korea offers pseudo-range correction information and monitors integrity of correction data by using multiple GNSS receivers. The maritime DGPS reference station and integrity monitor service sets alarm threshold value about integrity monitoring parameters for preventing service interruption status. However there is no way to avoid system interruption according to malfunction of backup systems and outside factors. Therefore, in this paper, warning threshold values were proposed for maritime DGPS operator can be counteract in advance. And Markov analysis method was carried out for selection of these warning threshold values.

• Journal of Navigation and Port Research
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• v.40 no.1
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• pp.15-20
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• 2016

In this study we measured a differential ASF to improve the accuracy of time synchronization with the signal transmitted from Pohang 9930M Loran station. We obtained the differential ASF which is calculated from a difference of the TOA measurements between KRISS and Chungnam National University(CNU), and KRISS and National Maritime PNT Office respectively. The TOA measurement at KRISS was measured by UTC(KRIS) reference clock and other sites were measured by atomic clocks respectively. The time variations of differential ASF measurements at CNU and National Maritime PNT Office were within $0.1{\mu}s$ and $0.05{\mu}s$ respectively. And we found the time variations of $0.1{\mu}s$ depending on the surrounding radio-wave environments from the differential ASF measurements of 60 minute moving averages. We can improve the accuracy of time synchronization of the local clock to within 10 ns by compensating the differential ASF through removing the common component of ASF. And we measured the absolute ASF between the Pohang transmit station and KRISS by the measurement technique of absolute time delay using a cesium atomic clock. The average ASF between two points is about $3.5{\mu}s$.

• Journal of Advanced Navigation Technology
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• v.21 no.3
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• pp.279-286
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• 2017

The international maritime organization(IMO) has defined performance requirements for future maritime navigation through IMO resolution A.915(22) in 2001. Many DGPS systems currently providing DGPS services do not meet the performance requirements specified in IMO resolution A.915(22). The use of SBAS is considered as one of the DGPS replacement and supplementary system for coping with the increase in demand performance and providing safe positioning service. In particular, since a large amount of budget is required to rearrange the existing DGPS reference stations, a method which transmits differential corrections generated by using SBAS message has been proposed. In this paper, we compare and analyze the performance of NDGPS which is operated by the National Maritime PNT Office of the ministry of oceans and fisheries(MOF) in Korea and MSAS in Japan. Also, we verify that SBAS, as alternative and complementary system, meets the performance requirement specified in IMO resolution A.915(22).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.279-282
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• 2015

Fisheries development of the basic law pursuant to article 15 (marine safety management, etc.) one of maritime safety and maritime traffic facilities nationwide network of DGPS in accordance with the building maximize infrastructure utilization and country. Source technology has been improving steadily raised for the benefit daegukmin. In particular, look at the type of product for the marine supply medium-wave receiver Performance products that satisfy most of the IMO Advisory. The antenna and receiver are separate structural supply for some integrated model with a very high Rather it is used as a portable receivers for marine positioning cheap integrated model development is needed. Correction of satellite navigation receivers for the current Marine GPS module, medium-wave modules can be developed one low cost Integrated in independent operating environments do not support the model development done look at what the problem is 285kHz ~ 315kHz in DGPS Beacon receiver structure using a medium wave or Beacon The medium-wave antenna and a GPS receiver signal to noise ratio was studied GPS signal attenuation on the DGPS performance looked at each GPS manufacturer medium-wave signal-to-noise ratio and normalized impact by GPS manufacturers noise power ratio per bandwidth for medium-wave GPS signals affect it was implemented to improve performance.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.525-529
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• 2022

In the eLoran system, the Loran Data Channel (LDC) is used to provide precise timing and positioning. The LDC message can be modulated with the Eurofix method, which modulates the transmission time of the 3rd-8th pulse not used for navigation, and the 9th pulse method, which modulates data using the 9th additional pulse after the existing 8 Loran pulses. In this paper, we analyzed the reception performance of the LDC message transmitted from the eLoran transmitter according to the modulation method. The eLoran testbed transmitter in Incheon was set to transmit LDC messages simultaneously with the 9th pulse modulation method and the Eurofix modulation method. Then, the LDC messages stored in the databases of the eLoran differential stations in Incheon and Pyeongtaek were analyzed in terms of the message reception rate according to the modulation method. Using the navigation aid management ship Inseong No. 1, the range of LDC message reception of actual sea users near Incheon Port was also analyzed. The results of this study are expected to be utilized in the full operational capability service after the eLoran pilot service.