• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.2
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• pp.171-178
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• 2008

Galileo is the Europe's global navigation satellite system corresponding to the GPS. The GIOVE-A test experiment has been finished and the second test satellite GIOVE-B will be launched soon. The integration of GPS and Galileo lead an increase of visible satellite number. We can obtain an improved navigation performance in signal blocked area such as urban or forest. GPS and Galileo have each time-coordinate system and use the different error model to calculate the navigation solution. In this paper, we studied on GPS and Galileo channel error model and time-coordinate system. Using this result, we implement the integrated navigation algorithm. In simulation, we analyzed the navigation error caused by time and coordinate disagreement and verified performance of integrated navigation algorithm in terms of visible satellite number, DOP(Dilution of Pression) and position error.

• Journal of Advanced Navigation Technology
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• v.25 no.3
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• pp.194-202
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• 2021

Ionosphere, one of the largest error sources, can pose potentially harmful threat to single-frequency GNSS (global navigation satellite system) user even after applying ionospheric corrections to their GNSS measurements. To quantitatively assess ionospheric impacts on the satellite navigation-based applications using simulation, the standard deviation of residual ionospheric errors is needed. Thus, in this paper, we determine conservative statistical quantity that covers typical residual ionospheric errors for nominal days. Extensive data-processing computes TEC (total electron content) estimates from GNSS measurements collected from the Korean reference station networks. We use Klobuchar model as a correction to calculate residual ionospheric errors from TEC (total electron content) estimate. Finally, an exponential delay model for residual ionospheric errors is presented as a function of local time and satellite elevation angle.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.229-238
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• 2022

This paper addresses on the International technical trends, standards, and development status of terrestrial radionavigation system to provide more accurate and fail-safe Positioning, Navigation, and Timing (PNT) Information available in maritime navigation environment. We analyze the performance result of pilot service in enhanced Long range navigation (eLoran) testbed environment using Low Frequency (LF) signal, and describe the development status of Ranging-Mode (R-Mode) system using Medium Frequency (MF) and Very High Frequency (VHF) to meet the Harbor Entrances and Approaches (HEA) requirement of International Maritime Organization (IMO) within 10m position accuracy. Furthermore, we present an architecture for integrated service of satellite-terrestrial navigation system and future maritime applicable fields. As the core information infrastructure of future navigation for 4th industrial revolution, this paper will be contributed to determining the direction of present and future to provide fail-safe PNT service with Global Navigation Satellite System (GNSS) based on the technical enhancement of terrestrial integrated navigation system.

• Journal of Aerospace System Engineering
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• v.4 no.1
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• pp.19-22
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• 2010

The accuracy and integrity of global navigation satellite systems (GNSS) can be improved by using GNSS augmentation systems. Large ionospheric spatial gradient, during ionosphere storm, is a major threat for using GNSS augmentation systems by increasing the spatial decorrelation between a reference system and users. Ionosphere decorrelation behavior can be analyzed by using dual frequency GPS data. GNSS receivers have their own biases, called inter-frequency bias (IFB) between dual(P1 and P2) frequencies and they must be accurately estimated before computing ionosphere delays. GPS network data in Korea is used to compute each receiver's IFB, and their estimation accuracy and variability are analyzed. IFB estimation methodology to apply for ionosphere gradient analysis is discussed.

• Journal of electromagnetic engineering and science
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• v.14 no.3
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• pp.299-305
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• 2014

A wideband circularly polarized (CP) antenna with a single feed is proposed for use in global navigation satellite systems. Its primary radiation elements are composed of two orthogonal bowtie dipoles, which are equipped with double-printed vacant-quarter rings to allow direct matching of the antenna to a single $50-{\Omega}$ coaxial line and to produce CP radiation. The crossed bowtie dipole is appropriately incorporated with a planar metallic reflector to produce the desired unidirectional radiation pattern as well as to achieve a wideband characteristic in terms of impedance matching and axial ratio (AR) bandwidths. The designed antenna was fabricated and measured. The prototype antenna with an overall 1.2-GHz frequency size of $0.48{\lambda}_o{\times}0.48{\lambda}_o{\times}0.25{\lambda}_o$ produced a measured ${\mid}S_{11}{\mid}$<-10 dB bandwidth of 1.05-1.79 GHz and a measured 3-dB AR bandwidth of 1.12-1.64 GHz. It also showed right-hand CP radiation with a small gain variation (${\pm}0.3dB$) and high radiation efficiency (>93%) over the operational bandwidth.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.6 no.12
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• pp.631-638
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• 2016

GNSS(Global Navigation Satellite System) such as GPS(Global Positioning System), GLONASS(GLObal NAvigation Satellite System) has been used in various fields for construction of geospatial inforamtion. But RTK or VRS method for high accuracy has some bad points like requirement of additional GNSS device and internet. So, this methods are difficult to take advantage of field survey. In this study, In this study, experiments using DGPS handheld devices and smart devices that can maximize mobility through was to suggest ways to improve the efficiency of field survey work. As a results, field survey work with smart devices is difficult to apply the limits of accuracy yet. On the other hand, DGPS has been found possible to determine the position accuracy within 1m. If DGPS is used in related work can greatly improve the efficiency of field survey work, which is currently much is done by hand, it is expected to serve as the basis for a structured GIS data management.

• Journal of Positioning, Navigation, and Timing
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• v.5 no.4
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• pp.181-191
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• 2016

A Satellite Based Augmentation System (SBAS) provides differential correction and integrity information through geostationary satellite to users in order to reduce Global Navigation Satellite System (GNSS)-related errors such as ionospheric delay and tropospheric delay, and satellite orbit and clock errors and calculate a protection level of the calculated location. A SBAS is a system, which has been set as an international standard by the International Civilian Aviation Organization (ICAO) to be utilized for safe operation of aircrafts. Currently, the Wide Area Augmentation System (WAAS) in the USA, the European Geostationary Navigation Overlay Service (EGNOS) in Europe, MTSAT Satellite Augmentation System (MSAS) in Japan, and GPS-Aided Geo Augmented Navigation (GAGAN) are operated. The System for Differential Correction and Monitoring (SDCM) in Russia is now under construction and testing. All SBASs that are currently under operation including the WAAS in the USA provide correction and integrity information about the Global Positioning System (GPS) whereas the SDCM in Russia that started SBAS-related test services in Russia in recent years provides correction and integrity information about not only the GPS but also the GLONASS. Currently, LUCH-5A(PRN 140), LUCH-5B(PRN 125), and LUCH-5V(PRN 141) are assigned and used as geostationary satellites for the SDCM. Among them, PRN 140 satellite is now broadcasting SBAS test messages for SDCM test services. In particular, since messages broadcast by PRN 140 satellite are received in Korea as well, performance analysis on GPS/GLONASS Multi-Constellation SBAS using the SDCM can be possible. The present paper generated correction and integrity information about GPS and GLONASS using SDCM messages broadcast by the PRN 140 satellite, and performed analysis on GPS/GLONASS Multi-Constellation SBAS performance and APV-I availability by applying GPS and GLONASS observation data received from multiple reference stations, which were operated in the National Geographic Information Institute (NGII) for performance analysis on GPS/GLONASS Multi-Constellation SBAS according to user locations inside South Korea utilizing the above-calculated information.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.8
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• pp.1951-1958
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• 2015

The paper is focused on not only the system characteristics of BeiDou, China GNSS, but also the statistic analysis based on its real data received from the BeiDou's satellite navigation messages. The 6-7 satellites, which are more than minimum number of 4 satellites to obtain 3-D position, are available for receiving navigation signal in stable case. It was also verified that the available satellites are deviated to specific coordinate and their signals are still unstable. Only as long as the received signal with the high stability, the precision of the BeiDou navigation satellite navigation system was identified with 5m level in deviation. The Beidou system is expected to be rising as a darkhorse in the future of the global satellite navigation area.

• Journal of Advanced Navigation Technology
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• v.19 no.1
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• pp.1-6
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• 2015

Due to the rapid increase in air traffic worldwide, ICAO has replaced the existing navigation equipment with equipment based on satellite navigation. As a part of that work, ICAO was planning to replace conventional takeoff and landing service using ILS with GBAS. Unlike ILS, GBAS which uses precision approach service inducing aircraft to airport and satellite based augmentation system providing precise position information service surrounding airport is capable of providing a required performance by only a system, regardless of the number of systems, and has an advantage that it is possible curved approach. In this paper, fuel reduction of ILS approach procedures and GBAS curved approach procedures is estimated and determined by flight test in Taean Airport.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.363-369
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• 2021

Since the Global Navigation Satellite System (GNSS) signal received from the low Earth orbit (LEO) satellite is only affected by the upper ionosphere, the magnitude of the ionospheric delay of Global Positioning System (GPS) signal received from ground user is different. Therefore, the ground-based two-dimensional ionospheric model cannot be applied to LEO satellites. The NeQuick model used in Galileo provides the ionospheric delay according to the user's altitude, so it can be used in the ionospheric model of the LEO satellites. However, the NeQuick model is not suitable for space receivers because of the high computational cost. A simplified NeQuick model with reduced computing time was recently presented. In this study, the computing time of the NeQuick model and the simplified NeQuick model was analyzed based on the GPS Klobuchar model. The NeQuick and simplified NeQuick model were applied to the GNSS data from GRACE-B, Swarm-C, and GOCE satellites to analyze the performance of the ionospheric correction and positioning. The difference in computing time between the NeQuick and simplified NeQuick model was up to 90%, but the difference in ionospheric accuracy was not as large as within 4.5%.