• International Journal of Aeronautical and Space Sciences
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• v.2 no.1
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• pp.55-66
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• 2001

The Global Positioning System(GPS) and the Strapdown Inertial Navigation System(SDINS) techniques have been widely utilized in many applications. However each system has its own weak point when used in a stand-alone mode. SDINS suffers from fast error accumulation dependent on an operating time while GPS has problem of cycle slips and just provides low update rate. The best solution is to integrate the GPS and SDINS system and its integration allows compensation for each shortcomings. This paper, first, is to define and derive error equations of integrated SDINS/GPS system before it will be applied on a real hardware system with gyro, accelerometer and GPS receiver. Second, the accuracy, availability and performance of this mechanization are verified on the simulation study.

• Journal of Advanced Navigation Technology
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• v.17 no.2
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• pp.157-164
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• 2013

In the presence of spoofing signal the GPS signal having the same PRN with the spoofer is hard to be acquired since the power of spoofing signal is usually stronger than that of GPS signal. If a spoofing signal exists for the same PRN, there are double peaks in two-dimensional space of frequency and code phase in acquisition stage. Using double peak information it is possible to detect spoofing signal and acquire GPS information through separate channel tracking. In this paper we introduce an anti-spoofing method using double peak detection, and thus can acquire GPS navigation data after two-channel tracking for the same PRN as the spoofing signal.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.4
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• pp.327-334
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• 2004

In this paper, a triplexer for Advanced Mobile Phone Service(AMPS), United States-Personal Communication Services(US-PCS), and Global Positioning System(CPS) is designed using L and C lumped elements. The triplexer shows the insertion loss of 0.6 ㏈, 1.1 ㏈, and 1.6 ㏈ for AMPS, US-PCS, and GPS bands, respectively. Also, it shows the attenuation characteristic of less than 18 ㏈, and the VSWR of less than 2.0 through the all pass-band.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.551-554
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• 2008

Do subject addition of existent picture reflex inside in this treatise as system that confirmation is available, do subject addition of picture reflex inside through GPS's photography position and Come on! direction angle of deviation campus to do confirmation possibility system design. Constructed each environment of Windows Operating System and embedded system environment for verification of system that is subject position of designed picture reflex also. To development environment of embedded system S3C2440A & used PXA270 processor, Camera and GPS in development baud, Come on! include deviation campus, and development language embodied in C language, and debugging environment did debugging using GCC compiler of Linux environment. PC software for verification designed system to confirm for subject position confirmation of picture reflex through Almap, Google Eartch developed verification software using visual C++. Also, groped way to utilize picture file by various field including position information within picture. Confirmed that decreased by error extent 1m within of radius 10m that is existent GPS's error extent as verification result.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2325-2330
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• 2003

GPS based orbit determination system for the KOMPSAT-2 has been developed. Two types of orbit determination software such as operational orbit determination and precise orbit determination are designed and implemented. GPS navigation solutions from on-board the satellite are used for the operational orbit determination and raw measurements data such as C/A code pseudo-range and L1 carrier phase for the precise orbit determination. Operational concept, architectural design, software implementation, and performance test are described.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.347-352
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• 2006

Narrowband interference can severely degrade the performance of GPS receivers. Detecting the presence of interference and then characterizing it can lead to its removal. Receivers can be reconfigured to focus on other signals or satellites that are less vulnerable to that interference at that moment. Using hardware reconfigurability of FPGA receivers and characterizing the effect of narrowband interference on the GNSS signal quality lead us to a new RFI mitigation technique in which the highest quality and less vulnerable signal can be chosen at each moment. In the previous work [1], the post processing capability of a software GPS receiver, has been used to detect and characterize the CW interference. This is achieved by passing the GPS signal and the interference through the correlator. Then, using the conventional definition of C/No as the squared mean of the correlator output divided by its variance, the actual C/No for each satellite is calculated. In this work, first the 'Exclusion zone' for each satellite signal has been defined and then by using some experiments the effects of different parameters like signal power, jamming power and the environmental noise power on the Exclusion zone have been analyzed. By monitoring the Doppler frequency of each satellite and using the actual C/No of each satellite using the traditional definition of C/No and actual data from a software GPS receiver, the decision to reconfigure the receiver to other signal can be made.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.2
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• pp.195-202
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• 1998

In this study, we utilized various type of GPS observation measurements to get a camera projection center of the aerial triangulation and consequently to determine which type is acceptable. For the accuracy and the error analysis, comparison between a projection center from the conventional model adjustment and the result determined by the kinematic DGPS positioning which is fitted to the conventional model adjustment using 3D conformal transformation method has been made. The camera projection center is located within a $\pm{2m}$ for C/A code range measurements, $\pm{14cm}$ for L1 phase measurements and $\pm{10cm}$ for L1/L2 phase measurements with $1\sigma$. In this way, the accuracy of the camera projection center by the bundle block adjustment can be predicted.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.329-330
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• 2011

This paper concerns to the acquisition of Global Positioning System L1 C/A coded signals. It specifically addresses the issues of acquiring very low power signals which are attenuated due to special circumstances such as indoor environment or forest canopy etc. The proposed post-processing algorithm applies modified signal folding coherent integration scheme on weak signal record. It dynamically compensates the doppler effect on the length of C/A code before integrating the signal power. Experimental results show effectiveness of the algorithm on weak GPS signals recorded in a real environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.2
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• pp.141-154
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• 2013

The technology of precise time-synchronization between signal receive devices for separation distance operation can be a key point for the technology with TDoA-based system. We propose a new method for the higher accuracy of system's time-synchronization in this paper, which uses OCXO and DPLL with high accuracy to achieve phase synchronization at 1 pps (pulse per second) of signal. And the method receive time value from a GPS satellite. Essentially, the performance of GPS with high accuracy refers to long-term frequency stability for its reliability. As per the characteristic, as the GPS timing signals are synchronized continuously, the accuracy of time-synchronization gets improved proportionally. Therefore, if the time synchronization is accomplished, the accuracy of the synchronization can be up to 0.001 ppb (part per billion). Through the improved accuracy of the time-synchronization, the measurement error of TDOA-based location detection technology is evaluated. Consequently, we verify that TDoA-based location measurement error can be greatly improved via using the improved method for time-synchronization error.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.235-240
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• 2006

Ionospheric scintillation induces a rapid change in the amplitude and phase of radio wave signals. This is due to irregularities of electron density in the F-region of the ionosphere. It reduces the accuracy of both pseudorange and carrier phase measurements in GPS/satellite based Augmentation system (SBAS) receivers, and can cause loss of lock on the satellite signal. Scintillation is not as strong at mid-latitude regions such that positioning is not affected as much. Severe effects of scintillation occur mainly in a band approximately 20 degrees on either side of the magnetic equator and sometimes in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. This paper focuses on estimation of the effects of ionospheric scintillation on GPS and SBAS signals using a software receiver. Software receivers have the advantage of flexibility over conventional receivers in examining performance. PC based receivers are especially effective in studying errors such as multipath and ionospheric scintillation. This is because it is possible to analyze IF signal data stored in host PC by the various processing algorithms. A L1 C/A software GPS receiver was developed consisting of a RF front-end module and a signal processing program on the PC. The RF front-end module consists of a down converter and a general purpose device for acquiring data. The signal processing program written in MATLAB implements signal acquisition, tracking, and pseudorange measurements. The receiver achieves standalone positioning with accuracy between 5 and 10 meters in 2drms. Typical phase locked loop (PLL) designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. So the effects of ionospheric scintillation was estimated on the performance of GPS L1 C/A and SBAS receivers in terms of degradation of PLL accuracy considering the effect of various noise sources such as thermal noise jitter, ionospheric phase jitter and dynamic stress error.