• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.08a
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• pp.175-178
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• 2008

In this paper, we introduce the considerations of pseudo range generation process of GNSS system and propose the design structure and show the simulation results applied to GPS. A Pseudo range generation simulator for GNSS(Global Navigation Satellite System) provides the generation function of GNSS constellations, the acquisition function of satellites position, the generation function of true range between satellites and user receiver, the generation functions for individual error features generated through the signal is travelled, and the calculation function of pseudo range. In addition, the simulator is designed to provide the output files of RINEX format.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.101-105
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• 2004

The purpose of the study is to develop ship's bearing sensor using CPS receiver which can play a role as a ship's secondary compass. In this research, two GPS receivers are used to determine the bearing in real time. Then we investigated the bearing accuracy associated with the error pattern of two GPS receivers. Especially, the results are as follows ; - The investigation on the system design of GPS-Compass - The modeling to compute heading of sailing - The analysis on bearing accuracy with the error pattern - The defining possibility to play a role as a ship's secondary compass

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.731-743
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• 2018

In this paper, a study result to decide the accuracy specifications of inertial sensors satisfying the performance requirements of SINS(ship's inertial navigation system) is proposed. To do this, the performance specifications of overseas SINS is surveyed and the detailed error analysis of SINS at stationary condition is performed. Also, a new performance index to indicate the performance of SINS is derived. Modelling and simulation results show that the accuracy specifications of inertial sensors to meet the performance requirements of SIGMA40XP, a typical overseas SINS, can be determined through the newly derived performance index in this paper.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.3
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• pp.269-275
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• 2024

On May 11, 2024, there was a strong solar flare explosion. A powerful geomagnetic storm triggered by a solar flare caused a major ionospheric disturbance over the Korean Peninsula. When a geomagnetic storm occurred, an abnormal change in vertical total electron content (VTEC) values was detected at all Global Navigation Satellite System (GNSS) stations in the Korean Peninsula. In addition, we performed GNSS precise point positioning (PPP) processing using observations from the SBAO and MKPO stations. We found that the up-directional position error increased significantly in both stations at around 17:00 UT on the day of year (DOY) 132, 2024. At that point, the root mean square (RMS) values for all position errors (East, North, and Up) increased compared to other dates. Due to very high noise, the L1 signal-to-noise ratio (SNR) values of QZSS pseudo-random noise (PRN) 07 dropped to about 25 dB. As a result, we suggest that the strong geomagnetic storm increased the GNSS PPP position errors in the Korean Peninsula.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.3
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• pp.49-57
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• 2002

In this paper, we deal with a real time implementation of the integrated image-based navigation parameter extraction system using the TMS320C80 MVP(multimedia video processor). Our system consists of relative position estimation and absolute position compensation, which is further divided into high-resolution aerial image matching, DEM(Digital elevation model) matching, and IRS (Indian remote sensing) satellite image matching. Those algorithms are implemented in real time using the MVP. To achieve a real-time operation, an attempt is made to partition the aerial image and process the partitioned images in parallel using the four parallel processors in the MVP. We also examine the performance of the implemented integrated system in terms of the estimation accuracy, confirming a proper operation of the our system.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.6
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• pp.77-81
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• 2008

In the deeply coupled GPS/INS integrated systems, if the integration filter update period is longer than the period of GPS navigation data, the loss of correlation values occurs due to the bit transition. This problem can be resolved when data wipe off(DWO) is used. However, general DWO methods requires heavy computation or cannot be applied continuously. This paper proposes an effective DWO method using carrier phase discriminator In order to show validity of the proposed method, simulations were carried out. The simulation results show that the data bit is accurately estimated and conform that the loss of correlation values and the error of code phase is small.

• Journal of Advanced Navigation Technology
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• v.6 no.2
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• pp.104-112
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• 2002

Nowadays, many countries are interested in using CPS far navigation system of aircrafts, because it has technical and economic benefits. For the CPS based navigation system, the most important thing is reliability of the system. GPS navigation solution is very accurate. But when some faults are raised in the CPS navigation system of an aircraft, if they cannot be detected and alerts are not generated for pilots, the aircraft cannot be safe. So, I implemented an DGPS integrity monitoring system that detects faults of measurements and exclude the fault measurement from the satellite constellation used for calculating a navigation solution. This paper introduces 'the Least Square Residual Method' used to detect faults of measurements and the implemented real time integrity monitoring system using DGPS. To test the system, I operated the system under many different conditions. And from analysis of the data recorded, I could conclude that when the number of visible satellites was enough to detect faults, the system could detect the faults of measurements perfectly, isolate and exclude the fault measurement well. But for more reliable system, the measurement errors must be estimated more accurately and integrations of CPS and other instruments must be developed.

• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.60-66
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• 2010

This paper deals with a post-processing of GPS receiver data in order to acquire a reference flight trajectory of an aircraft test. The flight test using an aircraft that is carried out several times since 2007 is the integrated test to verify the performance of the tracking and communications facilities in Naro Space Center and Jeju Tracking Center. In order to analyze performance of the tracking and navigation equipments, true reference data should be used for performance comparisons. Therefore off-the-shelf commercial GPS receiver, DL-V3 made by NovAtel Inc., is operated on the test to collect the GPS navigation data and the collected data is post-processed by GrafNav which is the off-the-shelf post-processing program made by NovAtel Inc. Through the post-processing of the collected data, a reference trajectory is generated with small error range about several decade centimeter level.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.2
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• pp.189-197
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• 2024

Galileo is a European Global Navigation Satellite System (GNSS) that has offered the Galileo Open Service since 2016. Consequently, the standardization of GNSS augmentation systems, such as Satellite Based Augmentation System (SBAS), Ground Based Augmentation System (GBAS), and Aircraft Based Augmentation System (ABAS) for Galileo signals, is ongoing. In 2023, the European Union Space Programme Agency (EUSPA) released prior probabilities of a satellite fault and a constellation fault for Galileo, which are 3×10^-5 and 2×10^-4 per hour, respectively. In particular, the prior probability of a Galileo constellation fault is significantly higher than that for the GPS constellation fault, which is defined as 1×10^-8 per hour. This raised concerns about its potential impact on GBAS integrity monitoring. According to the Global Positioning System (GPS) Standard Positioning Service Performance Standard (SPS PS), a constellation fault is classified as a wide fault. A wide fault refers to a fault that affects more than two satellites due to a common cause. Such a fault can be caused by a failure in the Earth Orientation Parameter (EOP). The EOP is used when transforming the inertial axis, on which the orbit determination is based, to Earth Centered Earth Fixed (ECEF) axis, accounting for the irregularities in the rotation of the Earth. Therefore, a faulty EOP can introduce errors when computing a satellite position with respect to the ECEF axis. In GNSS, the ephemeris parameters are estimated based on the positions of satellites and are transmitted to navigation satellites. Subsequently, these ephemeris parameters are broadcasted via the navigation message to users. Therefore, a faulty EOP results in erroneous broadcast ephemeris data. In this paper, we assess the conventional ephemeris fault detection monitor currently employed in GBAS for wide faults, as current GBAS considers only single failure cases. In addition to the existing requirements defined in the standards on the Probability of Missed Detection (PMD), we derive a new PMD requirement tailored for a wide fault. The compliance of the current ephemeris monitor to the derived requirement is evaluated through a simulation. Our findings confirm that the conventional monitor meets the requirement even for wide fault scenarios.

• Journal of Navigation and Port Research
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• v.38 no.4
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• pp.373-378
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• 2014

In order to prepare for recapitalization of differential GNSS (DGNSS) reference station and integrity monitor (RSIM) due to GNSS diversification, this paper focuses on differential correction algorithm using GPS/Galileo pesudorange. The technical standards on operation and broadcast of DGNSS RSIM are described as operation of differential GPS (DGPS) RSIM for conversion of DGNSS RSIM. Usually, in order to get the differential corrections of GNSS pesudorange, the system must know the real positions of satellites and user. Therefore, for calculating the position of Galileo satellites correctly, using the equation for calculating the SV position in Galileo ICD (Interface Control Document), it estimates the SV position based on Ephemeris data obtained from user receiver, and calculates the clock offset of satellite and user receiver, system time offset between GPS and Galileo, then determines the pseudorange corrections of GPS/Galileo. Based on a platform for performance verification connected with GPS/Galileo integrated signal simulator, it compared the PRC (pseudorange correction) errors of GPS and Galileo, analyzed the position errors of DGPS, DGalileo, and DGPS/DGalileo respectively. The proposed method was evaluated according to PRC errors and position accuracy at the simulation platform. When using the DGPS/DGalileo corrections, this paper could confirm that the results met the performance requirements of the RTCM.