• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1998.04a
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• pp.36-47
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• 1998

The test transimissionof DGPS correction data has been carried out since early 1996. The data has been sent from marine radiobeacon station at Changgi Gap Ligthouse. It was the first test brosdcast of DGPS correction data based on midium frequency of marine radiobeacon where transmission power and rate are 300W and 100bps respectively. However, there has not been any scientific study on the characteristic of the accuracy of a marine DGPS/radiobeacon. Accordingly. this paper investigates the accuracy of the system, which is currently operating in 310KHz. As a result , planned 8 reference station and coverage verified that the differential positioning accuray using themarine radiobeacon is sufficient to ensure the safetyof marine activities around the coast of Korea(position error of distance 107NM at reference station was about10m(drms)).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.282-288
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• 2014

The DGPS reference station is a national infrastructure generating GPS correctional information and transmitting the signal for Differential GPS. Currently, Korea has applied and operated the software-based DGPS reference station as a standard of the next generation proposed by the USCG in order to improve the hardware-based DGPS reference system. However, software-based DGPS reference station proposed by USCG was changed in software method, only for form. There is no advantage to changing software-based because the most critical part of architecture has not been improved. In this paper, we have designed a new software-based marine DGPS station architecture that a reference station software and a monitor station were integrated. The new marine DGPS station architecture based on software is a more simplified structure than it used to be and can be utilized in the DGPS reference station.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.9
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• pp.1822-1829
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• 2016

DGPS Reference station is established in Korea for improvement of GPS navigation accuracy and needs of integrity. Recently, DGPS stations provide user positioning information on land as well as ocean. However, this paper investigated visibility and interference environment for performance degradation of Chung-ju DGPS reference station. In case of Young-do reference station, visibility and interference environment were satisfied with reference standard. In case of Chung-ju reference station, visibility was satisfied with 7 degree elevation angle. However, interference environment was not satisfied with reference standard of -50dBm. This paper proposed time differential measurement analysis method excluding error of signal noise for analyzing measurement error. Chung-ju reference station measurement analysis result is three times the error than on Young-do in Dec, 2015. In addition, this paper has confirmed measurement performance degradations because of reference station equipment problem. Future study will be carried out performance analysis of 17 DGPS reference station.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.437-443
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• 2014

Based on the radio wave propagation measurement of DGPS land-based reference stations, the DGPS service coverage and signal quality in the receiving points are analyzed in this paper. The DGPS signal strength and SNR in the receiving point are measured in the winter and summer season, respectively. In case of DGPS reference station that can not provide the designed service coverage, the solution to improve the service coverage is presented in this paper. Almost all DGPS reference station except reference station with low ground conductivity or mountainous terrain provide the DGPS service coverages of 80% or more of the designed service area. The service coverages of DGPS reference stations can be improved to pre-designed service area in case of installation management of DGPS site on the plain terrain and good ground conductivity. It is necessary to get the high efficiency of transmitting antenna to improve the service area.

• Journal of Navigation and Port Research
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• v.35 no.9
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• pp.701-706
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• 2011

Radio waves including GPS signals, various TV communications, and radio broadcasting can be disturbed by a strong solar storm, which may occur due to solar flares and produce an ionospheric delay anomaly in the ionosphere according to the change of total electron content. Electron density irregularities can cause deep signal fading, frequently known as ionospheric scintillation, which can result in the positioning error using GPS signal. This paper proposes a detection algorithm for the ionosphere delay anomaly during a solar storm by using multi-reference stations. Different TEC grid which has irregular electron density was applied above one reference station. Then the ionospheric delay in zenith direction applied different TEC will show comparatively large ionospheric zenith delay due to the electron irregularity. The ionospheric slant delay applied an elevation angle at reference station was analyzed to detect the ionospheric delay anomaly that can result in positioning error. A simulation test was implemented and a proposed detection algorithm using data logged by four reference stations was applied to detect the ionospheric delay anomaly compared to a criterion.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.12
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• pp.1690-1696
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• 2014

Network RTK generates spatial corrections by using differenced measurements from reference stations in the network, and the corrections are then provided to a rover. The rover, generally, uses linear interpolation, which assumes that the corrections at each reference station are spatially correlated, to obtain a precise correction of its location. However, an irregularity of the tropospheric delay is a real-world factor that violates this assumption. Tropospheric delay is a result of weather conditions, such as humidity, temperature and pressure, and it can cause spatial decorrelation when there are changes in the local climate. In this paper, we have defined the non-linear characteristics of the tropospheric delay between reference stations or user within a region as the "irregularity of tropospheric delay". Such an irregularity can negatively impact the network RTK performance. Therefore, we analyze the influence of the irregularity of tropospheric delay in network RTK based on meteorological data.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.402-408
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• 2021

GNSS-Reflectometry (GNSS-R) is a technique for measuring and analyzing signals transmitted from satellites, reflecting on the surface of land or sea. GNSS-R is mainly used for measuring the water level variation, typhoon and meteorological anomaly, soil moisture, and snow depth. This paper describes the concept and measurement principle of GNSS-R technology, especially focusing on the field of marine utilization and its feasibility. In particular, it presents the applications of this technique for monitoring the safety of marine environment as well as the marine vessel and their utilization areas based on currently available infrastructure on the ground and maritime reference stations, such as the existing differential GNSS reference stations and integrity monitors (DGNSS RSIM), and GNSS reference station infrastructure, using the ground-based and the satellite-based GNSS-R approaches.

• Journal of Navigation and Port Research
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• v.45 no.1
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• pp.26-32
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• 2021

In ocean field, the spread of the Fourth Industrial Revolution based on information and communication technology requires high precision and stable PNT&D (Position, Navigation, Timing and Data). As the IMO (International Maritime Organization) and IALA (The International Association of Marine Aids to Navigation and Lighthouse Authorities) are requiring backup systems due to mitigate vulnerabilities and the increase of dependency on GNSS (Global Navigation Satellite System), Korea is conducting a research & development of R-Mode. An DGPS (Differentiate Global Positioning System) reference station that uses MF, an existing maritime infrastructure, and AIS (Automatic Identification System) base stations that use 34 integrity station and VHF will be utilized in this study to avoid redundant investment. Because there are radio shadow areas that display low signal levels in the west sea, the establishment of new R-Mode reference and integrity station will be intended to resolve problems regrading the radio shadow area. Because the frequency has a characteristic in that radio wave transmits well along the ground (water surface) in low frequency band, simulation and measurement were conducted therefore this paper to propose candidate sites for R-Mode reference and integrity station resulted through p wave's propagation characteristics analysis. Using this paper, R-Mode reference and integrity station can be established at appropriate locations to resolve radio shadow areas in other regions.

• Journal of Navigation and Port Research
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• v.31 no.6
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• pp.509-514
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• 2007

The importance of the GPS is becoming larger and larger since it is one of the Global Navigation Satellite Systems and is regarded as a national infrastructure in the field positioning and timing Nowadays many researches avoiding and/or minimizing economic loss caused by unexpected fault of the GPS are being carried out because GPS fault can give a large impact on social security system as well as economic system NDGPS network which has been authorized by the Ministry of Marine and Fisheries provides services for marine users and evolved into a national infrastructure for GNSS users. Many researchers and engineers are doing research work in order to apply the NDGPS network to other fields. From this trend, it can be expected that the integrity and related functions for the NDGPS users will become more important than before. This paper analyzes integrity informations about the real GNSS fault and proposes method on integrity monitoring improvement of the DGPS reference station.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.11
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• pp.2569-2575
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• 2015

Network RTK generally uses a linear interpolation method by using the corrections from reference stations. This minimizes the spatial decorrelation error caused by the increase of distance between the reference station's baseline and user's baseline. However, tropospheric delay, a function of the meteorological data can cause a spatial decorrelation characteristic among reference stations within a network by local meteorological difference. A non-linear characteristic of tropospheric delay can deteriorate Network RTK performance. In this paper, the modeling of tropospheric delay irregularity is made from the data when the typhoon is occurred. By using this modeling, analyzing the effect of meteorological difference between reference stations on correction is performed. Finally, we analyze an effect of non-linear characteristics of tropospheric delay among reference stations to Network RTK user.