• Title, Summary, Keyword: GNSS integrity monitoring

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Development of Remote Integrity Monitoring System for GNSS (GNSS 원격 무결성 감시시스템 개발)

  • Bae, Jung-Won;Song, Jae-Hun;Jeon, Hyang-Sik;Nam, Gi-Uk;Lee, Han-Seong
    • Aerospace Engineering and Technology
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    • v.5 no.2
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    • pp.16-26
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    • 2006
  • GNSS is a satellite-based radio navigation aid. For using it in civil air navigation area, any GNSS service should meet the requirements of accuracy, integrity, continuity and availability in each flight phase established by ICAO. In this study, a remote integrity monitoring system(RIMS) for GNSS are proposed and explained to utilize it in the design of GNSS augmentation system such as GBAS and GRAS. The RIMS consists of signal-in-space receiving subsystem and signal processing subsystem. Each GPS receiver is connected to Host PC by the serial to ethernet converting device which is able to convert serial port connection to LAN port connection in order to exchange information via the internet. We can overcome the siting limitation of GPS receiver and antenna, and reduce signal loses in the cable between GPS antenna and receiver. This system is providing the development environment for GBAS CAT-I system.

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A Study on Integrity Monitoring Improvement of the DGPS Reference Station (DGPS 기준국 무결성 감시 체계 고도화 방안 연구)

  • Cho, Deuk-Jae;Park, Sang-Hyun;Choi, Jin-Kyu;Suh, Sang-Hyun
    • 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.

Method for Detection and Identification of Satellite Anomaly Based on Pseudorange (의사거리 기반 위성 이상 검출 및 식별 기법)

  • Seo, Ki-Yeol;Park, Sang-Hyun;Jang, Won-Seok;Kim, Young-Ki
    • Journal of Korean Institute of Intelligent Systems
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    • v.22 no.3
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    • pp.328-333
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    • 2012
  • Current differential GPS (DGPS) system consists of reference station (RS), integrity monitor (IM), and control station (CS). The RS computes the pseudorange corrections (PRC) and generates the RTCM messages for broadcasting. The IM receives the corrections from the RS broadcasting and verifies that the information is within tolerance. The CS performs realtime system status monitoring and control of the functional and performance parameters. The primary function of a DGPS integrity monitor is to verify the correction information and transmit feedback messages to the reference station. However, the current algorithms for integrity monitoring have the limitations of integrity monitor functions for satellite outage or anomalies. Therefore, this paper focuses on the detection and identification methods of satellite anomalies for maritime DGPS RSIM. Based on the function analysis of current DGPS RSIM, it first addresses the limitation of integrity monitoring functions for DGPS RSIM, and then proposes the detection and identification method of satellite anomalies. In addition, it simulates an actual GPS clock anomaly case using a GPS simulator to analyze the limitations of the integrity monitoring function. It presents the brief test results using the proposed methods for detection and identification of satellite anomalies.

Multiple-Hypothesis RAIM Algorithm with an RRAIM Concept (RRAIM 기법을 활용한 다중 가설 사용자 무결성 감시 알고리듬)

  • Yun, Ho;Kee, Changdon
    • The Journal of Advanced Navigation Technology
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    • v.16 no.4
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    • pp.593-601
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    • 2012
  • This paper develops and analyzes a new multiple-hypothesis Receiver Autonomous Integrity Monitoring (RAIM) algorithm as a candidate for future standard architecture. The proposed algorithm can handle simultaneous multiple failures as well as a single failure. It uses measurement residuals and satellite observation matrices of several consecutive epochs for Failure Detection and Exclusion (FDE). The proposed algorithm redueces the Minimum Detectable Bias (MDB) via the Relative RAIM (RRAIM) scheme. Simulation results show that the proposed algorithm can detect and filter out multiple failures in tens of meters.

A Fault Detection and Exclusion Algorithm using Particle Filters for non-Gaussian GNSS Measurement Noise

  • Yun, Young-Sun;Kim, Do-Yoon;Kee, Chang-Don
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.2
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    • pp.255-260
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    • 2006
  • Safety-critical navigation systems have to provide 'reliable' position solutions, i.e., they must detect and exclude measurement or system faults and estimate the uncertainty of the solution. To obtain more accurate and reliable navigation systems, various filtering methods have been employed to reduce measurement noise level, or integrate sensors, such as global navigation satellite system/inertial navigation system (GNSS/INS) integration. Recently, particle filters have attracted attention, because they can deal with nonlinear/non-Gaussian systems. In most GNSS applications, the GNSS measurement noise is assumed to follow a Gaussian distribution, but this is not true. Therefore, we have proposed a fault detection and exclusion method using particle filters assuming non-Gaussian measurement noise. The performance of our method was contrasted with that of conventional Kalman filter methods with an assumed Gaussian noise. Since the Kalman filters presume that measurement noise follows a Gaussian distribution, they used an overbounded standard deviation to represent the measurement noise distribution, and since the overbound standard deviations were too conservative compared to the actual distributions, this degraded the integrity-monitoring performance of the filters. A simulation was performed to show the improvement in performance of our proposed particle filter method by not using the sigma overbounding. The results show that our method could detect smaller measurement biases and reduced the protection level by 30% versus the Kalman filter method based on an overbound sigma, which motivates us to use an actual noise model instead of the overbounding or improve the overbounding methods.

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A Warning Threshold Proposal for Operation Improvement of Maritime DGPS Reference Station (해양용 DGPS 운영성 개선을 위한 시스템 경고 임계값 제안)

  • Choi, Yong Kwon;Lee, Ju Hyun;Son, Seok Bo;Lee, Sang Jeong
    • The 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.

Multi-constellation Local-area Differential GNSS for Unmanned Explorations in the Polar Regions

  • Kim, Dongwoo;Kim, Minchan;Lee, Jinsil;Lee, Jiyun
    • Journal of Positioning, Navigation, and Timing
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    • v.8 no.2
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    • pp.79-85
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    • 2019
  • The mission tasks of polar exploration utilizing unmanned systems such as glacier monitoring, ecosystem research, and inland exploration have been expanded. To facilitate unmanned exploration mission tasks, precise and robust navigation systems are required. However, limitations on the utilization of satellite navigation system are present due to satellite orbital characteristics at the polar region located in a high latitude. The orbital inclination of global positioning system (GPS), which was developed to be utilized in mid-latitude sites, was designed at $55^{\circ}$. This means that as the user is located in higher latitudes, the satellite visibility and vertical precision become worse. In addition, the use of satellite-based wide-area augmentation system (SBAS) is also limited in higher latitude regions than the maximum latitude of signal reception by stationary satellites, which is $70^{\circ}$. This study proposes a local-area augmentation system that additionally utilizes Global Navigation Satellite System (GLONASS) considering satellite navigation system environment in Polar Regions. The orbital inclination of GLONASS is $64.8^{\circ}$, which is suitable in order to ensure satellite visibility in high-latitude regions. In contrast, GLONASS has different system operation elements such as configuration elements of navigation message and update cycle and has a statistically different signal error level around 4 m, which is larger than that of GPS. Thus, such system characteristics must be taken into consideration to ensure data integrity and monitor GLONASS signal fault. This study took GLONASS system characteristics and performance into consideration to improve previously developed fault detection algorithm in the local-area augmentation system based on GPS. In addition, real GNSS observation data were acquired from the receivers installed at the Antarctic King Sejong Station to analyze positioning accuracy and calculate test statistics of the fault monitors. Finally, this study analyzed the satellite visibility of GPS/GLONASS-based local-area augmentation system in Polar Regions and conducted performance evaluations through simulations.

Fault Detection Performance Analysis of GNSS Integrity RAIM (GNSS 무결성을 위한 RAIM 기법의 고장검출 성능 분석)

  • Kim, Ji Hye;Park, Kwan Dong;Kim, Du Sik
    • Journal of Korean Society for Geospatial Information System
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    • v.20 no.3
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    • pp.49-56
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    • 2012
  • Performance analysis on RAIM, which is one of the techniques for monitoring integrity to ensure the reliability of GPS, was conducted in this study. RAIM is such a method which allows its user to monitor integrity in the stand-alone mode. Among the existing RAIM procedures, the representative methods including the RCM (Range Comparison Method), LSRM (Least Square Residual Method), Parity approach and WRAIM (Weighted RAIM) were evaluated, and their performance was analyzed. To validate the performance of the implemented algorithms, fault detection was tried on the clock malfunctioning event of PRN 23 occurred on January 1st, 2004. As a result, it was identified that the LSRM and the WRAIM detected all the faults happened in the event. In the case of RCM, all the states of fault were detected except for the error which occurred as a false alarm at one epoch. Furthermore, simulated biases were added for each satellite to analyze the sensitivity of each algorithm. Consequently, when biases of the 9-13 meters range were simulated for the RCM and LSRM algorithm, all the malfunctions were detected. For the WRAIM method, it could detect range biases greater than 15 meters.

Ionospheric Storm and Spatial Gradient Analysis for GBAS

  • Kim, Jeong-Rae;Yang, Tae-Hyoung;Lee, Young-Jae;Jun, Hyang-Sig;Nam, Gi-Wook
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.361-365
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    • 2006
  • High ionospheric spatial gradient during ionospheric storm is most concern for the landing approach with GNSS (Global Navigation Satellite System) augmentation systems. In case of the GBAS (Ground-Based Augmentation System), the ionospheric storm causes sudden increase of the ionospheric delay difference between a ground facility and a user (aircraft), and the aircraft position error increases significantly. Since the ionosphere behavior and the storm effect depend on geographic location, understanding the ionospheric storm behavior at specific regional area is crucial for the GNSS augmentation system development and implementation. Korea Aerospace Research Institute and collaborating universities have been developing an integrity monitoring test bed for GBAS research and for future regional augmentation system development. By using the dense GPS (Global Positioning System) networks in Korea, a regional ionosphere map is constructed for finding detailed aspect of the ionosphere variation. Preliminary analysis on the ionospheric gradient variation during a recent storm period is performed and the results are discussed.

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Analysis on the Multi-Constellation SBAS Performance of SDCM in Korea

  • Lim, Cheol-Soon;Park, Byungwoon;So, Hyoungmin;Jang, Jaegyu;Seo, Seungwoo;Park, Junpyo;Bu, Sung-Chun;Lee, Chul-Soo
    • 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.