[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

This literature review paper focuses on existing vulnerabilities associated with global navigation satellite systems (GNSSs). With respect to the civilian/non encrypted GNSSs, they are employed for proving positioning, navigation and timing (PNT) solutions across a wide range of industries. Some of these include electric power grids, stock exchange systems, cellular communications, agriculture, unmanned aerial systems and intelligent transportation systems. In this survey paper, physical degradations, existing threats and solutions adopted in academia and industry are presented. In regards to GNSS threats, jamming and spoofing attacks as well as detection techniques adopted in the literature are surveyed and summarized. Also discussed are multipath propagation in GNSS and non line-of-sight (NLoS) detection techniques. The review also identifies and discusses open research areas and techniques which can be investigated for the purpose of enhancing the robustness of GNSS.

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GNSS Vulnerabilities and Existing Solutions: A Review of the Literature

Global Navigation Satellite System (GNSS) provides all-weather, precise Position, Velocity and Timing (PVT) solutions from any point on the surface or near to the surface of the earth. Accuracy and...

Precision of satellite based navigation position solution: A review using NavIC data

The positioning systems’ high accuracy and reliability are crucial enablers for various future applications, including autonomous shipping worldwide. It is especially challenging for the Arctic region due to the lower number of visible satellites, severe ionospheric disturbances, scintillation effects, and higher delays than in the non-Arctic and non-Antarctic regions. In regions up North, conventional satellite positioning systems are generally proposed to be utilized, together with other situational awareness systems, to achieve the necessary level of accuracy. This paper provides a detailed review of the current state-of-the-art, satellite-based positioning systems’ availability and performance and reports high-level positioning requirements for the oncoming applications. In particular, the comparative study between three Global Navigation Satellite System (GNSS) constellations is executed to determine whether they are suitable for autonomous vessel navigation in the Arctics’ complex environment as the two most significant drivers for a reevaluation of the related satellite constellations. This work analyzes the ongoing research executed in different (inter-) national projects focused on Galileo, Global Positioning System (GPS), and GLObal NAvigation Satellite System (GLONASS). Based on the literature review and the simulation campaign, we conclude that all the convectional constellations achieve an accuracy of fewer than three meters in the analyzed Arctic scenarios. It is postulated that other complementary positioning methods should be utilized to improve accuracy beyond this limit. Finally, the study emphasizes existing challenges in the Arctic region regarding the localization and telecommunication capabilities and provides future research directions.

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Positioning in the Arctic Region: State-of-the-Art and Future Perspectives

Requirement of accuracy and reliability of position solution obtained from satellite-Based navigation system provided by the Global Navigation Satellite System (GNSS) depends on the application. In some cases, meter level precision is required while cm or mm level accuracy is required for other precision applications. Surveying is one of the important applications of GNSS. Surveying of forest is a challenge for survey engineers in determining accurate position, because satellite signals frequently fade by stems and leaves of the tress. Consequently, the observables become noisy that affects quality of position solution. Real Time Kinematic (RTK) is a popular GNSS positioning method used in case of various precision applications. High cost receivers may provide better RTK solution those are not affordable for many surveyors. Low cost, single frequency, multi-GNSS enabled receiver are available in market those can provide raw data and can be used for RTK. In this paper an effort is presented to assess the precision and reliability of position solution obtained from the low-cost receivers within Indian forest environments. In the first case study over a short baseline, position solution precision provided by a low-cost Rover operating in forest is studied, and meter level of precision is achieved in GPS+GLONASS+Galileo mode. In second case study for long baseline RTK operation, reliable solution is obtained in GPS+Galileo+QZSS mode from a low-cost Rover operating within forest environment. So, reliable or precise position solution can be achieved using low cost receivers and suitable multi-GNSS combination under forest canopy.

Low Cost GNSS Receiver RTK Performance in Forest Environment

Augmentation of GNSS Utility by IRNSS/ NavIC Constellation Over the Indian Region

Global navigation satellite systems (GNSSs) is currently used in myriads of applications and at the same time internet-based applications are also growing. In case of GNSS, stand-alone, single receiver-based position solution accuracy may not be enough in many applications like automated transporting service, unmanned air vehicle, Geodesy and agriculture etc and GNSS mass market needs low cost high accurate position solution. Carrier phase measurement-based position solution is more precise than code-based measurement, but phase ambiguity is a problem in carrier phase-based measurement. Real time Kinematic (RTK) technique is a method where precise position solution can be obtained using Network Transfer of RTCM message through IP (NTRIP) protocol; here multiple signal messages (MSM) are also sent from the GNSS base station to the rover and Carrier ambiguity can be resolved. This research work focuses on the RTK performance of geodetic, survey-grade receivers and low-cost receivers and analysis on their comparative performances. Geodetic receiver uses its own algorithm to calculate RTK solution and for the low-cost receivers, an open-source GNSS data processing software, RTKLib has been used. A static survey is made and found that low cost receivers can provide sub meter level precision in RTK operation which may help in GNSS mass market application and solution development.

Preliminary Results on the Performance of Cost-effective GNSS Receivers for RTK

In a multi-GNSS (global navigation satellite system) environment with operational GPS, GLONASS and Galileo Satellites, the Asia–Oceania region is expected to get better benefits of a large number of GNSS satellites for use. However, it is witnessed that during some parts of the day, no GNSS satellite is present above 60° elevation angle from many parts of the earth, including India. Real-time data from India show the regular absence of usable GPS satellites above 60° elevation angles during some parts of the day; addition of GLONASS and Galileo satellites does not improve the situation much. From Burdwan, West Bengal, India at least twice a day, no GNSS satellite is found above 60° elevation angles for more than 30 min. Simulation study for scattered places of India and data from IGS Centres confirm similar observations, except for the extreme northern region. The global scenario also supports these observations, while the individual operator’s country is free from the problem using their own navigational system. The consequences of the problem affect GNSS-based solutions; for locations with obstruction of GNSS signals from low elevation angles, the concurrent occurrence of this incidence poses a threat for seamless GNSS-based navigation through intermittent loss of solution and degraded solution quality. Regional navigation satellite systems (RNSS) help mitigate this problem within the respective service regions. For a large part of the globe, the problem may be allayed using GNSS–RNSS hybrid operation. The result would be important for location-specific GNSS mission planning in strategic, life and safety-critical applications.

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Sukabya Dan

Papers

Augmentation of GNSS Utility by IRNSS/ NavIC Constellation Over the Indian Region

Preliminary Results on the Performance of Cost-effective GNSS Receivers for RTK

Precision of satellite based navigation position solution: A review using NavIC data

Low Cost GNSS Receiver RTK Performance in Forest Environment

Visibility Anomaly of GNSS Satellite and Support from Regional Systems