• Journal of Positioning, Navigation, and Timing
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• 제13권1호
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• pp.35-44
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• 2024

This investigation primarily focuses on the generational characteristics of satellites utilized in the existing Global Navigation Satellite System (GNSS) and Regional Navigation Satellite System (RNSS), with a central emphasis on comparing the operational status of the latest generation satellites. Variations among satellite generations in physical attributes, energy consumption, and timekeeping are observed, enabling an exploration of the developmental trends over successive generations. Through a comparative analysis of the latest generation satellites, particularly in terms of performance, this study aims to furnish essential insights into the satellites employed within each system. Consequently, it will contribute to a foundational understanding of the past, present, and future GNSS satellites.

• Journal of Positioning, Navigation, and Timing
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• 제11권3호
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• pp.181-189
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• 2022

The public open signals from Global Navigation Satellite System (GNSS) including Global positioning system (GPS) are used widely by many peoples in the world except for the public regulated restriction signals which are encrypted. Nowadays there are growing concerns about GNSS signal spoofing which can deceive the GNSS receivers by abusing these open services. To counter these spoofing threats, many researches have been studied including array antenna techniques which can detect the direction of arrival by means of Multiple Signal Classification (MUSIC) algorithm. Originally the array antenna techniques were developed to countermeasure the jamming signal in electronic warfare by using the nulling or beamforming algorithm toward a certain direction. In this paper, we study the anti-spoofing techniques using array antenna to overcome the jamming and spoofing issues simultaneously. First, we will present the theoretical analysis results of spoofing signal response of Minimum Variance Distortionless Response (MVDR) algorithm in array antenna. Then the eigenvector algorithm of covariance matrix is suggested and verified to work with the existing anti-jamming method. The modeling and simulation are used to verify the effectiveness of the anti-spoofing algorithm. Also, the field test results show that the array antenna system with the proposed algorithms can perform the anti-spoofing function. This anti-spoofing method using array antenna is very effective in the view point of solving both the jamming and spoofing problems using the same array antenna hardware.

• 전기전자학회논문지
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• 제24권2호
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• pp.461-467
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• 2020

오늘날 민간에서 사용 중인 측위 시스템의 대부분은 위성의 신호를 수신하여 현재 위치를 계산하는 글로벌 위성항법 시스템(GNSS; Global Navigation Satellite System)을 기반으로 한다. 미국이 GPS (Global Positioning System)를 통하여 입증한 GNSS의 효용성은 다양한 국가에서 위성항법 시스템을 구축하고 고도화 하도록 이끌었다. 그중 중국은 앞선 IT 기술력과 자금력을 바탕으로 자체 GNSS인 베이더우 위성항법 시스템(BDS; BeiDou Navigation Satellite System)의 급진적인 개발을 성공시켰다. 중국이 빠르게 전 세계로 BDS의 서비스 영역을 확대하고 있는 것을 고려할 때 우리나라에서도 BDS에 대한 체계적인 연구가 요구된다. 따라서 본 논문에서는 BDS의 공개 신호인 B1C에 대한 전반적인 정보를 제공하여 B1C 신호 체계 설계 및 BDS B1C 수신기 설계에 활용될 수 있도록 한다.

• 한국항행학회논문지
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• 제21권1호
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• pp.58-65
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• 2017

위성항법시스템은 위성을 이용하여 측위정보를 불특정다수에게 동시 제공하는 서비스되도록 시스템이 구성되어 있어, 태양풍, 태양흑점활동, 전리층 산란 등과 같은 자연적 원인으로 인한 교란뿐만 아니라 전파방해 및 기만신호 등의 여러 가지 이유로 신호의 무결성을 확보하는데 근본적인 취약성을 지니고 있다. 무인항공기 시스템은 비행체의 측위정보 오입력의 경우 시계 비행 등의 즉각적인 대응이 불가능해 위성항법신호의 무결성 침해 위협이 추락에 준하는 사고 및 대량 피해로 연결될 가능성이 크다. 따라서 무인항공기 시스템의 비행안전성 증진을 위해서는 전파방해 및 기만신호에 대응할 수 있는 보완적 위성항법시스템을 사용이 요구된다. 본 논문에서는 위성항법시스템이 지닌 위협 원인 및 대응 기술을 살펴보고, 국내외 무인항공기에 적용된 위성항법시스템 적용 동향과 위성항법시스템의 위협으로 인해 파급될 수 있는 무인항공기 시스템의 비행안전성 위협 영향성을 분석하고, 무인항공기 시스템의 비행안전성 확보를 위한 위성항법시스템 기능 무력화에 대한 기술적, 제도적 대응방안을 모색하고자 한다.

• 한국항해항만학회지
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• 제29권8호
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• pp.763-770
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• 2005

위성을 이용한 측위 시스템인 광역위성항법시스템(GNSS : Global Navigation Satellite System)은 측량 및 항법 등에 정확한 위치, 속도 그리고 시간 정보를 제공함으로써 위치결정의 중요한 도구가 되어왔다. 미 국방성에 의해 개발되어 운용되고 있는 범세계적위치결정시스템인 GPS는 GNSS 시장에 독점적인 존재이므로, GNSS 사용자는 GPS에 의존할 수 밖에 없는 상황이다. 이런 독점 상황을 극복하기 위하여 러시아, 유럽 그리고 일본은 독자적인 위성항법시스템을 개발하기 시작하였다. 특히 유럽의 Galileo 시스템은 2008년 발사 목표로 진행되고 있다. 본 연구는 위성궤도를 생성하고 분석할 수 있도록 제작한 GIMS2005 프로그램을 이용하여 차세대 GNSS인 Galileo 시스템을 GPS와 비교 분석함에 있다. 본 실험은 GPS 단독 처리의 한계와 GPS/Galileo 결합 시스템의 이점을 인식할 수 있게 한다. 기하구조 분석은 가시위성수, 정밀도 저하율, 내부 신뢰도 그리고 외부 신뢰도를 GPS 단독 처리와 비교하여 분석된다.

• Journal of Positioning, Navigation, and Timing
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• 제8권4호
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• pp.201-208
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• 2019

Numerical integration is necessary for satellite orbit determination and its prediction. The numerical integration algorithm can be divided into single-step and multi-step method. There are lots of single-step and multi-step methods. However, the Runge-Kutta method in single-step and the Adams method in multi-step are generally used in global navigation satellite system (GNSS) satellite orbit. In this study, 4th and 8th order Runge-Kutta methods and various order of Adams-Bashforth-Moulton methods were used for GLObal NAvigation Satellite System (GLONASS) orbit integration using its broadcast ephemeris and these methods were compared with international GNSS service (IGS) final products for 7days. As a result, the RMSE of Runge-Kutta methods were 3.13m and 4th and 8th order Runge-Kutta results were very close and also 3rd to 9th order Adams-Bashforth-Moulton results. About result of computation time, this study showed that 4th order Runge-Kutta was the fastest. However, in case of 8th order Runge-Kutta, it was faster than 14th order Adams-Bashforth-Moulton but slower than 13th order Adams-Bashforth-Moulton in this study.

• Journal of Positioning, Navigation, and Timing
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• 제12권4호
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• pp.343-348
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• 2023

The ionosphere acts as the largest error source in the Global Navigation Satellite System (GNSS) signal transmission. Ionospheric total electron content (TEC) is also easily affected by changes in the space environment, such as solar activity and geomagnetic storms. In this study, we analyze changes in the regional ionosphere using the Qusai-Zenith Satellite System (QZSS), a regional satellite navigation system. Observations from 9 GNSS stations in South Korea are used for estimating the QZSS TEC. In addition, the performance of QZSS TEC is analyzed with observations from day of year (DOY) 199 to 206, 2023. To verify the performance of our results, we compare the estimated QZSS TEC and CODE Global Ionosphere Map (GIM) at the same location. Our results are in good agreement with the GIM product provided by the CODE over this period, with an averaged difference of approximately 0.1 TECU and a root mean square (RMS) value of 2.89 TECU.

• 한국항공운항학회지
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• 제15권1호
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• pp.11-17
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• 2007

One of the key elements for developing GNSS (Global Navigation Satellite Systems) is the comprehensive analysis of GNSS satellite orbit including the capabilities to generate precision navigation message. The orbit characteristics of Japan's own GNSS system, called QZSS (Quasi Zenith Satellite System) is analyzed and its navigation message, which includes orbit elements and correction terms, is investigated. QZSS-type orbit simulations were performed using a precision orbit integrator in order to analyze the effect of perturbation forces, e.g. gravity, Moon, Sun, etc., on the orbit variation. A preliminary algorithm for creating orbit element corrections was developed and its accuracy is evaluated with the simulation data.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.113-119
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• 2023

Satellite navigation systems, with the exception of the GLObal NAvigation Satellite System (GLONASS), adopt ionosphere models and provide ionospheric coefficients to single-frequency users via navigation messages to correct ionospheric delay, the main source of positioning errors. A Global Navigation Satellite System (GNSS) mostly has its own ionospheric models: the Klobuchar model for Global Positioning System (GPS), the NeQuick-G model for Galileo, and the BeiDou Global Ionospheric delay correction Model (BDGIM) for BeiDou satellite navigation System (BDS)-3. On the other hand, a Regional Navigation Satellite System (RNSS) such as the Quasi-Zenith Satellite System (QZSS) and BDS-2 uses the Klobuchar Model rather than developing a new model. QZSS provides its own coefficients that are customized for its service area while BDS-2 slightly modifies the Klobuchar model to improve accuracy in the Asia-Pacific region. In addition, BDS broadcasts multiple ionospheric parameters depending on the satellites, unlike other systems. In this paper, we analyzed the different ionospheric models of GPS, QZSS, and BDS in Korea. The ionospheric models of QZSS and BDS-2, which are based in Asia, reduced error by at least 25.6% compared to GPS. However, QZSS was less accurate than GPS during geomagnetic storms or at low latitude. The accuracy of the models according to the BDS satellite orbit was also analyzed. The BDS-2 ionospheric model showed an error reduction of more than 5.9% when using GEO coefficients, while in BDS-3, the difference between satellites was within 0.01 m.

• Journal of Positioning, Navigation, and Timing
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• 제4권3호
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• pp.141-150
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• 2015

In this study, a Global Navigation Satellite System (GNSS) / Inertial Navigation System (INS) / odometer / barometer integrated navigation system that uses a commercial navigation device including Micro Electro Mechanical Systems (MEMS) accelerometer and gyroscope in addition to GNSS, odometer information obtained from a vehicle, and a separate MEMS barometer sensor was implemented, and the performance was verified. In the case of GNSS and GNSS/INS integrated navigation system that are generally used in a navigation device, the performance would deteriorate in areas where GNSS signals are not available. Therefore, an integrated navigation system that calculates a better navigation solution in areas where GNSS signals are not available compared to general GNSS/INS by correcting the velocity error of GNSS/INS using an odometer and by correcting the cumulative altitude error of GNSS/INS using a barometer was suggested. To verify the performance of the navigation system, a commercial navigation device (Softman, Hyundai Mnsoft, http://www.hyundai-mnsoft.com) and a barometer sensor (ST Company) were installed at a vehicle, and an actual driving test was performed. To examine the performance of the algorithm, the navigation solutions of general GNSS/INS and the GNSS/INS/odometer/barometer integrated navigation system were compared in an area where GNSS signals are not available. As a result, a navigation solution that has a smaller position error than that of GNSS/INS could be obtained in the area where GNSS signals are not available.