• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.402-408
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• 2021

GNSS-Reflectometry (GNSS-R) is a technique for measuring and analyzing signals transmitted from satellites, reflecting on the surface of land or sea. GNSS-R is mainly used for measuring the water level variation, typhoon and meteorological anomaly, soil moisture, and snow depth. This paper describes the concept and measurement principle of GNSS-R technology, especially focusing on the field of marine utilization and its feasibility. In particular, it presents the applications of this technique for monitoring the safety of marine environment as well as the marine vessel and their utilization areas based on currently available infrastructure on the ground and maritime reference stations, such as the existing differential GNSS reference stations and integrity monitors (DGNSS RSIM), and GNSS reference station infrastructure, using the ground-based and the satellite-based GNSS-R approaches.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.4
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• pp.1-5
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• 2016

As a dependency on Global Navigation Satellite System (GNSS) becomes increase in various applications, its reliability has been very important. However, in South Korea, Global Positioning System (GPS) jamming incident happened four times since 2010. GNSS signal is so weak that it is highly susceptible to all types of the jamming. GNSS jamming can cause serious damage in the safety-critical applications based on the GNSS. In this paper, we present the GNSS jamming signal propagation prediction simulator based on ITU-R P.1546 model. This simulator is developed for preventing or reducing the damage from the GNSS jamming attack by predicting the jamming propagation strength based on the geographical information in Korean peninsula.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.4
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• pp.239-247
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• 2022

The existing studies on the localization in the GNSS (Global Navigation Satellite System) denied environment usually exploit low-cost MEMS IMU (Micro Electro Mechanical Systems Inertial Measurement Unit) sensors to replace the GNSS signals. However, the navigation system still requires GNSS signals for the normal environment. This paper presents an integrated GNSS/INS (Inertial Navigation System) navigation system which combines GNSS and multiple IMU sensors using extended Kalman filter in partially GNSS-denied environments. The position and velocity of the INS and GNSS are used as the inputs to the integrated navigation system. The Mahalanobis distance is used for novelty detection to detect the outlier of GNSS measurements. When the abnormality is detected in GNSS signals, GNSS data is excluded from the fusion process. The performance of the proposed method is evaluated using MATLAB/Simulink. The simulation results show that the proposed algorithm can achieve a higher degree of positioning accuracy in the partially GNSS-denied environment.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.153-155
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• 2006

A major advantage of the area in and around Braunschweig is its concentration of major research institutes and small to large enterprises dealing with different modes of transportation. For many years, aviation has been a particular focus. The research institutes have aircraft and helicopters equipped especially for research projects, as well as other laboratory equipment, allowing simulation and testing of air traffic application both virtually and on real aircraft. In addition, with the Luftfahrtbundesamt (equivalent organization to FAA) and the Bundesstelle $f{\"{u}}r$ Flugunfalluntersuchung (equivalent to NTSB) both located at the Research Airport, it enables direct contact with two key air-traffic safety authorities. The institutes of DLR and the Technical University of Braunschweig are very active in rail transportation applications. Cooperation with the market leader in rail automation - Siemens Rail Automation, also located in Braunschweig - and with other companies in the Braunschweig region means that safety-critical road applications and mobility research is available due to the activities of a number of institutes. Cooperation with Volkswagen (VW) and other companies in the region ensure access to the market leaders' know-how in this sector. Current European activities within framework of the Galileo project offer particularly good opportunities for the Research Airport to leverage its expertise and position itself internationally as a specialist in safety-critical transport applications - the centre is an initiative of Niedersachsen and the Ministry of Economic Affairs, Labour and Transport Location and navigation plays a central role in all modes of transport - air, road and rail. The market is being revolutionized by the increasing integration of GNSS. The realization of the Galileo system will provide additional opportunities for the Research Airport: Galileo as a civil operated system offers service guarantees especially in the area of safety-critical applications in transportation. Notably standards, processes and authorizations related to the certification of safety-critical applications in the areas of air, road and rail transportation are still to be determined. GAUSS, located at the Research Airport Braunschweig, as an European centre of excellence for simulation, testing and certification of safety-critical applications can offer its expertise to validate the services guaranteed by the Galileo concessionaire.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.27-31
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• 2006

GNSS Services and Applications are today in permanent evolution in all the market sectors. This evolution comprises: ${\bullet}$ New constellations and systems, being GALILEO probably the most relevant example, but not the only one, as other regions of the world also dwell into developing their own elements (e.g. the Chinese Beidou system). ${\bullet}$ Modernisation of existing systems, as is the case of GPS and GLONASS ${\bullet}$ New Augmentation services, WAAS, EGNOS, MSAS, GRAS, GAGAN, and many initiatives from other regions of the world ${\bullet}$ Safety of Life services based on the provision of integrity and reliability of the navigation solutions through SBAS and GBAS systems, for aeronautical or maritime applications ${\bullet}$ New Professional applications, based on the unprecedented accuracies and integrity of the positioning and timing solutions of the new navigation systems with examples in science (geodesy, geophysics), Civil engineering (surveying, construction works), Transportation (fleet management, road tolling) and many others. ${\bullet}$ New Mass-market applications based on cheap and simple GNSS receivers providing accurate (meterlevel) solutions for daily personal navigation and information needs. Being on top of this evolving market requires an active participation on the key elements that drive the GNSS development. Early access to the new GNSS signals and services and appropriate testing facilities are critical to be able to reach a good market position in time before the next evolution, and this is usually accessible only to the large system developers as the US, Europe or Japan. Jumping into this league of GNSS developers requires a large investment and a significant development of technology, which may not be at range for all regions of the world. Bearing in mind this situation, MAGIC appears as a concept initiated by a small region within Europe with the purpose of fostering and supporting the development of advanced applications for the new services that can be enabled by the advent of SBAS systems and GALILEO. MAGIC is a low cost platform based on the application of technology developed within the EGNOS project (the SBAS system in Europe), which encompasses the capacity of providing real time EGNOS and, in the near future, GALILEO-like integrity services. MAGIC is designed to be a testing platform for safety of life and liability critical applications, as well as a provider of operational services for the transport or professional sectors in its region of application. This paper will present in detail the MAGIC concept, the status of development of the system within the Madrid region in Spain, the results of the first on-field demonstrations and the immediate plans for deployment and expansion into a complete SBAS+GALILEO regional augmentation system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.12
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• pp.1216-1227
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• 2013

GNSS(Global Navigation Satellite System) is now being widely used in both civilian and military applications where accurate positioning and timing information are required and it is considered as a representative convergence technique in IT-Military application techniques. However, GNSS has low sensitivity level of GNSS receivers and is vulnerable to jamming signal, since the signals come from the satellite located at approximately 20,000 Km above the earth. The studies for the anti-jamming techniques in military applications have been passively performed in the domestic, because the information related GNSS are dependent on the countries that have GNSS. In this paper, we show the effect of jammer ERP by analyzing the link budget of GPS J/S power as a function of distance between jammer and receiver. Also, we categorize the anti-jamming techniques based on the functional block diagram of GNSS receiver structure and analyze the recent anti-jamming GNSS products and their technologies developed in domestic and foreign countries.

• Spatial Information Research
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• v.18 no.5
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• pp.1-11
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• 2010

Since January 2009, Seoul Metro Government(SMG) is operating own Network RTK Systems connecting four(4) GNSS Reference Stations which are installed inside Seoul Metro City area. SMG is currently providing VRS data service via wireless internet for Network-RTK and RINEX data observed from GNSS Reference Stations. This paper will discuss utilization of data available from SMG Network-RTK System for various applications, and present the test results on practicalities of Virtual RINEX data. For the utilization of data available from SMG Network- RTK system, 1)NTRIP data delivery of GNSS realtime observables streaming and converting to RINEX at receiving side, 2) monitoring deformation of bulky structures using GNSS observation were discussed. In addition to those discussion, 3) broadcasting VRS correction data for job site via radio modem after acquiring such correction data on-line using NTRIP based GNSS Internet Radio from SMG Network-RTK System were introduced. For the test results on practicalities of Virtual RINEX data, 1) the post-processing results of the GNSS observation data on a certain point with GNSS Reference Station data have been compared to the post-processing results of Virtual RINEX data on the same point generated from SMG Network-RTK System, and 2) VRS RTK positioning results for a certain point and post-processing results of Virtual RINEX data for the point were compared. The results showed only a few mm difference, and the high possibility for using Virtual RINEX data for post-processing applications.

• Journal of Advanced Navigation Technology
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• v.25 no.3
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• pp.194-202
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• 2021

Ionosphere, one of the largest error sources, can pose potentially harmful threat to single-frequency GNSS (global navigation satellite system) user even after applying ionospheric corrections to their GNSS measurements. To quantitatively assess ionospheric impacts on the satellite navigation-based applications using simulation, the standard deviation of residual ionospheric errors is needed. Thus, in this paper, we determine conservative statistical quantity that covers typical residual ionospheric errors for nominal days. Extensive data-processing computes TEC (total electron content) estimates from GNSS measurements collected from the Korean reference station networks. We use Klobuchar model as a correction to calculate residual ionospheric errors from TEC (total electron content) estimate. Finally, an exponential delay model for residual ionospheric errors is presented as a function of local time and satellite elevation angle.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1483-1488
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• 2012

This paper analyzed the precision and accuracy of the altitude-aided GNSS using the altitude information from digital map. The precision of altitude-aided GNSS is analysed using the theoretically derived DOP. It is confirmed that the precision of altitude-aided GNSS is superior to the general 3D positioning method. It is also shown that the DOP of altitude-aided GNSS is independent of altitude bias error while the accuracy was influenced by the altitude bias error. Furthermore, it is shown that, since the altitude bias error influenced differently to each pseudorange measurement, the effect of the altitude bias error is more serious than clock bias error which does not influence position error at all. The results are evaluated by the simulation using the commercial RF simulator and GPS receiver. It confirmed that altitude-aided GNSS could improve not only precision but also accuracy if the altitude bias error are small. These results are expected to be easily applied for the performance improvement to the land and maritime applications.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.1
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• pp.9-16
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• 2015

The applications of Global Navigation Satellite System (GNSS) receivers are becoming wider in various commercial and military systems including even small weapon systems such as artillery shells. The precision-guided munitions such as Small Diameter Bomb (SDB) of United States can be used for pinpoint strike by acquiring and tracking GNSS signals in high mobility situation. In this paper, a small GNSS receiver with embedded interference suppression capability working under high dynamic stress is developed which is applicable to the various weapon systems and can be used in other several harsh environments. It applies a kind of matched filter and multiple correlator schemes for fast signal acquisition and tracking of even weak signals and frequency domain signal processing method to eliminate the narrowband interference. To evaluate the performance of the developed GNSS receiver, the test scenario of high mobility and interference environment with the GNSS simulator and signal generator is devised. Then, the signal acquisition time, navigation accuracy, sensitivity, and interference suppression performances under high dynamic operation are evaluated. And the comparison test with the commercial GNSS receiver which has high sensitivity is made under the same test condition.