• Journal of Positioning, Navigation, and Timing
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• v.1 no.1
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• pp.29-34
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• 2012

A software GNSS signal generator for the GPS L1/L2/L5 and Galileo E1/E5 signals is proposed in this paper. And this signal generator is designed and implemented with several components by considering the reuse and expansion of components for similar GNSS signals. The characteristics of the reusability of the components are confirmed with the carrier generation and the band-pass filter components. And the functionality of the GNSS multi-band IF signal generator is validated by using the commercial software GPS L1 receiver, and the performance of signal acquisition, tracking and accuracy of horizontal position error are analyzed for this validation. As a result, the GPS L1 signal generator operates successfully and it could be expected that other signal generators also operate well because most of components are the same as those of the GPS L1 signal generator.

• Journal of The Korean Association For Science Education
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• v.21 no.3
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• pp.566-579
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• 2001

The purpose of this study was to investigate students' actual thinking processes during conceptual change about free fall. To do this, middle school students were made an interview designed based on a teaching model using thought experiment. From the study, it was found that strategy for generating cognitive conflict by suggesting opposite views was not effective. However, many students changed their prior conceptions when new explanatory hypothesis, which explained why heavy object and light object fall equally, was introduced. And finally, even though students realized that the changed idea did not accord with the real world, they could easily solve that problem by observing demonstration designed to show the effect of air resistance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.11
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• pp.947-957
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• 2014

In this paper, the navigation performance analysis techniques of a pseudolite navigation system are proposed. To validate the techniques, operation and navigation test results using real test data are addressed. The conventional navigation performance analysis methods used for satellite navigation system, such as Galileo and GPS, are analyzed to identify the error factor and to check the criterion of UERE defined in the standard document. And then the method to calculate the UERE through the ranging measurements are studied. By identifying the error factor in pseudolite navigation system based on these methods, the available UERE observation and calculation method applicable to pseudolite navigation are proposed. Simulation results considering various circumstances and the actual flight test results are presented to verify the proposed method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.6
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• pp.910-915
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• 2018

The precise time, which is an essential element of the Global Navigation Satellite System (GNSS), such as US GPS, GLONASS in Russia, Galileo in Europe, and Beidou in China, is an important foundation for various economic activities around the world. Communication systems, power grids, IoT, Cloud computing and financial networks operate based on the precise time not only for the operating principles, but also for the synchronization and operational efficiency between tasks. In this paper, we introduce the Atomium software for the first time in South Korea. Atomium was developed by ORB in Belgium to calculate the clock error(clock solution) with GNSS signal observation data based on PPP method. The observation data is provided by Korea Research Institute of Standards and Science(KRISS). The results of MJD57106 with Atomium software are presented.

• Journal of the Korean Society for Library and Information Science
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• v.32 no.1
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• pp.27-43
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• 1998

This article examines the current status and future trends in library and information services in USA, with particular emphasis on the library automation system, library cooperation, Internet andinformation services, activities of information services organizations. Client/server computing and integrated Web-based technology make it possible for libraries to build a new generation of automated library systems, and digital libraries project is the highest priority. As a cooperative effort among libraries, they formed consortia such as ARL/AAU on the national level. and CIC on the regional level, and GALILEO, LLN, OhioLink, Texshare, VIVA, ILLINET on the state level information netwok. The Internet and the World Wide Web have a huge impact, so American libraries are developing new skills to provide value-added information services using Internet resources. Lastly, recent information activities of the LC, NAL, NLM, ERIC, NTIS are described.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.1
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• pp.89-95
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• 2009

The accuracy and efficiency of RTK-GPS is proved through its measurement, but it is not used in cadastral detail surveying, due to low accuracy caused by the trouble of satellite reception in a built-up area and lack of detailed guidelines for practical application. Thus, this study tries to offer detailed directions for the practical use of RTK-GPS by analyzing the application problem of RTK-GPS measurement. As results of the study, for the practical use of RTK-GPS it suggests enactment of regulations, connection of practical RTK-GPS measurement with the existing detail surveying methods, introduction of a VRS method for increasing the arrangement density of reference stations, and integrated use of GPS, GLONASS and Galileo satellites for securing accuracy and stability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1217-1224
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• 2008

The carrier tracking has to be basically completed for accurate positioning of Galileo satellite system. The FLL for tracking frequency errors is robust to dynamic stress causing changes of propagation time but hardly tracks accurate carrier tracking. The PLL for tracking phase errors provides accurate carrier tracking but is sensitive to dynamic stress and its tracking performance is decreased when high dynamics exist. In this paper, we design the carrier tracking loop with the FLL-assisted PLL loop filter and co-operations of FLL and PLL to achieve accurate carrier tracking in high dynamic stress. we prove the performance of designed carrier tracking loop via simulations.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.211-215
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• 2006

In this paper, design and applications of a generalized, versatile and customizable IF signal generator that can model the modernized GPS and Galileo signal is given. It generates IF sampled data that can be directly used by a software receiver. Entire constellation of satellites which is independent of satellite-user geometry is easily determined using a real or simulated ephemeris data. Since the IF center frequency, sampling frequency and quantization bit number are user location dependent parameters, their effects are also considered in IF signal generator. The generalized IF signal generator will be very well suited for the development phase of a software receiver due to its versatility. The full access to the sampling frequency, front-end filter definition and ADC parameters also offers a great opportunity for cost-effective analysis of tracking loops and error mitigation techniques at the receiver level. Interference sources can be easily added to the generator to simulate specific environments. This software IF signal generator can also be used to feed a multi-frequency multi-system software receiver for the prototyping of a combined GPS/Galileo receiver. The test result using the generated signals and a real software receiver shows the effectiveness of the implemented IF signal generator.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.471-474
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• 2009

A Hanbitho, which is a ship to measure maritime transportation system, observes and estimates the maritime transportation system and its signal to be able to receive in our closed sea New GNSS systems are constructed such as GLONASS, GALILEO, QZSS, however, our ships can use SBAS service such as MSAS of Japan. So, it is needed to reconstruct new measuring system to observe and estimate new GNSS and SBAS. In this paper, we propose the upgrade method of Hanbiho measuring system.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.331-336
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• 2002

Satellite positioning technology has been widely used in all kinds of military and civil land, marine, space and aeronautical target positioning tasks, navigation activities and accurate surveying measurements since 90s in the last century due to it advantage in providing all-weather, real-time, three dimensional and high precision positioning information, as well as speed and accurate timing information. By now, it has already formed a new hi-tech industry basically. This paper briefly reviews the development of the global satellite positioning and navigation technologies including the basic information of China′s "Plough navigation system", introduces the history of satellite positioning technology and its major application fields as well as the status quo of this being industrialized trade in China, gives an account of the writers′ vision for the application and prospect of the satellite positioning technologies in China, and approaches the tactics and stresses of the satellite positioning technology′s application and its industrialization future in China.