• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.10
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• pp.946-951
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• 2011

This paper presents the simulation results of GBAS availability and requirement (with respected to Vertical Protection Level) using simulated data at CAT I, CAT II/III DH point (Decision Height), which are generated using Jeju international GNSS reference position, aircraft horizontal velocity and reference/aircraft GNSS antenna performance index and so on. Two kinds of protection levels are presented, one is from a hypothesis (H0) and other is from a alternative hypothesis (H1). These protection levels are compared with AL (Alert Limit), and we analyse the GBAS availability and requirement for CAT I and CAT II/III at the airport.

• Journal of Positioning, Navigation, and Timing
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• v.5 no.1
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• pp.11-20
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• 2016

In this paper, a system that can collect GPS L1 C/A, GLONASS G1, and BDS B1I signals with single front-end receiver was implemented using a universal software radio peripheral (USRP) and its performance was verified. To acquire the global navigation satellite system signals, hardware was configured using USRP, antenna, external low-noise amplifier, and external oscillator. In addition, a value of optimum local oscillator frequency was selected to sample signals from three systems with L1-band with a low sampling rate as much as possible. The comparison result of C/N0 between the signal collection system using the proposed method and commercial receiver using double front-end showed that the proposed system had 0.7 ~ 0.8dB higher than that of commercial receiver for GPS L1 C/A signals and 1 ~ 2 dB lower than that of commercial receiver for GLONASS G1 and BDS B1I. Through the above results, it was verified that signals collected using the three systems with a single USRP had no significant error with that of commercial receiver. In the future, it is expected that the proposed system will be combined with software-defined radio (SDR) and advanced to a receiver that has a re-configuration channel.

• Journal of Astronomy and Space Sciences
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• v.23 no.4
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• pp.385-396
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• 2006

The International GNSS Service (IGS) has prepared for a transition from the relative phase conte. variation (PCV) to the absolute PCV, because the terrestrial scale problem of the absolute PCV was resolved by estimating the PCV of the GPS satellites. Thus, the GPS data will be processed by using the absolute PCV which will be an IGS standard model in the near future. It is necessary to compare and analyze the results between the relative PCV and the absolute PCV for the establishment of the reliable processing strategy. This research analyzes the effect caused by the absolute PCV via the GPS network data processing. First, the four IGS stations, Daejeon, Suwon, Beijing and Wuhan, are selected to make longer baselines than 1000km, and processed by using the relative PCV and the absolute PCV to examine the effect of the antenna raydome. Beijing and Wuhan stations of which the length of baselines are longer than 1000km show the average difference of 1.33cm in the vertical component, and 2.97cm when the antenna raydomes are considered. Second, the 7 permanent GPS stations among the total 9 stations, operated by Korea Astronomy and Space Science Institute, are processed by applying the relative PCV and the absolute PCV, and their results are compared and analyzed. An insignificant effect of the absolute PCV is shown in Korea regional network with the average difference of 0.12cm in the vertical component.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.505-514
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• 2014

The effects of reflected wave of the sea on pseudolite ranging accuracy are analysed in this paper, when a pseudolite navigation system is used for wide area outdoor applications such as aircraft and vessels positioning. Methods for minimizing the influence of sea surface reflection wave were proposed. The methods include the appropriate correlator in pseudolite navigation system through the correlation performance comparison analysis in receiver design, the use of the technology of multiple antennas, and locating the transmitting station antenna on an appropriate position. From the results of experiments, the method of locating the antenna position shows the most reliable performance against the effect of surface reflection wave. The analysis results of the ranging accuracy improvement are addressed, when the multipath caused by sea surface reflection exists.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.4
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• pp.21-30
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• 2012

This paper presents site survey processes and the results for installing GBAS Category-I ground system into Gimpo international airport. For siting assessment, many things should be taken into account in advance, such as installation requirement of GBAS components, future airport development plan and possible interference effects to existing facilities. Because overall performance of GBAS system can be affected by GPS signal reception environment, on-site survey should be performed carefully to measure actual GPS environmental performance and determine if any adverse multipath or RFI problems exist or not. In addtion, VDB antenna should be located to ensure line of sight for transmitting VHF signal to deliver GBAS message to aircraft. Based on the survey results, final location for GBAS system installation is selected near runway 32 in the Gimpo airport.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.178-181
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• 2005

The positioning accuracy of the Global Positioning System (GPS) has been improved considerably during the past two decades. The main error sources such as ionospheric refraction, orbital uncertainty, antenna phase center variation, signal multipath, and tropospheric delay have been reduced substantially, if not eliminated. In this study, the GPS data collected by the GPS receivers that were established as continuously operating reference stations by International GNSS Service (IGS), Ministry of the Interior (MOl), Central Weather Bureau (CWB), and Industrial Technology Research Institute (ITRI) Of Taiwan are utilized to investigate the impact of atmospheric water vapor on GPS positioning determination. The surface meteorological measurements that were concurrently acquired by instruments co-located with the GPS receivers include temperature, pressure and humidity data. To obtain the influence of the GPS height on the proposed impact study. A hydrodynamic ocean tide model (GOTOO.2 model) and solid earth tide were used to improve the GPS height. The surface meteorological data (pressure, temperature and humidity) were introduced to the data processing with 24 troposphere parameters. The results from the studies associated with different GPS height were compared for the cases with and without a priori knowledge of surface meteorological measurements. The finding based on the measurements in 2003 is that the surface meteorological measurements have an impact on the GPS height. The associated daily maximum of the differences is 1.07 cm for the KDNM station. The impact is reduced due to smoothing when the average of the GPS height for the whole year is considered.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.80-81
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• 2012

Our society consist of many country's critical infrastructure such as production and distribution of electric power systems, communications technology, tele-communications, financial system, transportation systems when those systems are operated efficiently and normally. Country's critical infrastructure and its application fields of this magnitude rely on more and more P.N.T (Positioning, Navigation. Timing) systems, in which the tele-communications(Timing), financial market(Timing), logistics (Positioning, Navigation, Timing), transportation(Positioning, Navigation. Timing) is shoring. Reliability concerned about the exact position and timing of these critical national infrastructure rely on ability to provide a stable from GPS.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.1
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• pp.10-15
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• 2016

In this study, The code-carrier divergence test was applied to GPS measurements, and the results were compared and analyzed. The GPS data used for the threshold determination were obtained from Global Navigation Satellite System permanent stations built by the Korea Aerospace Research Institute. At each permanent station, identical dual-frequency receiver and choke ring antenna with radome are installed. The analysis method, root mean square values were compared and analyzed for each permanent station and satellite. As a result, the root mean square value generally decreased as the satellite elevation angle increased although the trend was gentle. Threshold were finally selected based on the average and standard deviation of root mean square for each permanent station. For improving of availability and continuity in real-time operation when the threshold is over the limits, Code-Carrier divergence test values are initialized.

• Proceedings of the KSRS Conference
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• v.2
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• pp.748-751
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• 2006

Positioning accuracy by the Global Positioning System (GPS) is of great concern in a variety of research tasks. It is limited due to error sources such as ionospheric effect, orbital uncertainty, antenna phase center variation, signal multipath, and tropospheric influence. In this study, the tropospheric influence, primarily due to water vapour inhomogeneity, on GPS positioning height is investigated. The data collected by the GPS receivers along with co-located surface meteorological instruments in 2003 are utilized. The GPS receivers are established as continuously operating reference stations by the Ministry of the Interior (MOI), Central Weather Bureau (CWB), and Industrial Technology Research Institute (ITRI) of Taiwan, and International GNSS Service (IGS). The total number of GPS receivers is 21. The surface meteorological measurements include temperature, pressure, and humidity. They are introduced to GPS data processing with 24 troposphere parameters for the station heights, which are compared with those obtained without a priori knowledge of surface meteorological measurements. The results suggest that surface meteorological measurements have an expected impact on the GPS height. The daily correction maximum with the meteorological effect may be as large as 9.3 mm for the cases of concern.

• Journal of Positioning, Navigation, and Timing
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• v.3 no.4
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• pp.155-161
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• 2014

The purpose of this study is to develop precise point positioning (PPP) algorithms based on GLONASS code-pseudorange, verify their performance and present their utility. As the basic correction models of PPP, we applied Inter Frequency Bias (IFB), relativistic effect, satellite antenna phase center offset, and satellite orbit and satellite clock errors, ionospheric errors, and tropospheric errors that must be provided on a real-time basis. The satellite orbit and satellite clock errors provided by Information-Analytical Centre (IAC) are interpolated at each observation epoch by applying the Lagrange polynomial method and linear interpolation method. We applied Global Ionosphere Maps (GIM) provided by International GNSS Service (IGS) for ionospheric errors, and increased the positioning accuracy by applying the true value calculated with GIPSY for tropospheric errors. As a result of testing the developed GLONASS PPP algorithms for four days, the horizontal error was approximately 1.4 ~ 1.5 m and the vertical error was approximately 2.5 ~ 2.8 m, showing that the accuracy is similar to that of GPS PPP.