• 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.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.108-114
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• 2014

This paper describes the orbit accuracy of KOMPSAT-5, which has been in normal operations since the launch on Aug. 22, 2013. The analysis on the various GPS related data and the different methodologies for orbit estimation are carried out and compared with each other. The accuracy of precise orbit is confirmed to be 12.8cm($1{\sigma}$) on average using data from the in-flight dual frequency GPS receiver, GPS precise ephemeris, and IGS stations. In addition, the orbit estimation using single frequency GPS receiver provides the orbit solution around 2m level. And, the accuracy of orbit processing is 5m using on-board navigation solution, which has about 10m accuracy.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.35 no.6
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• pp.573-580
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• 2017

Precise stochastic modeling for GPS measurements is one of key factors in adjustment computations for GPS positioning. To analyze the GPS measurement errors, Minimum Norm Quadratic Unbiased Estimators(MINQUE) approach is used in this study to estimate the variance components for measurement types with short-baseline GPS positioning model. The results showed the magnitudes of measurement errors for C1, P2, L1, L2 are 22.3cm, 27.6cm, 2.5mm, 2.2mm, respectively. To reduce the memory usage and computational burden, variance components are also estimated on epoch-by-epoch basis. The results showed that there exists slight differences between the solutions. However, epoch-by-epoch analysis may also be used for most of GPS applications considering the magnitudes of the differences.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.10a
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• pp.81-86
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• 2003

As the utility value of GPS in surveying field is on the increase after the conversion into the world geodetic system, it is attracting the interest of many people involved in the application of GPS. In this study an algorithm was established settling ambiguity through LAMBDA techniques and the baseline processing program was developed for L1/L2 carrier phase using visual c++ 6.0, which is an object-oriented language. And the developed program proved that it maintained a difference of less than 3mm over the short baseline of 1.5m or shorter when compared with other commercialized programs.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.8
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• pp.765-772
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• 2006

The L2 Civil Signal (L2CS) will be transmitted by modernized IIR(IIR-M), IIF and all subsequent GPS satellites. It contains two codes of different length; CM code contains 10,230chips, repeats every 20milliseconds and is modulated with message data, and CL code contains 767,250chips, repeats every 1.5second Z-count and has no data modulation. And the message data is encoded for Forward Error Correction(FEC). The long code length is useful for weak signal, but it also requires very long acquisition time. Therefore, the structure of GPS Ll/L2C Correlator and the fast acquisition scheme are proposed in this paper.

• Journal of Astronomy and Space Sciences
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• v.11 no.1
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• pp.71-80
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• 1994

It is generally known that the measurement of the ionospheric total electron content(TEC) by GPS can more accurately monitor the broader area of the ionosphere than other current methods. \Ve measured the TEC along a slant path considering the arrival time differences of P-code which is transmitted from GPS satellites with the modulation on two L-band carrier frequencies, L1 (1574.42MHz) and L2 (1227.60MHz). Under the assumptions that the ionosphere is uniformly distributed and its average height is 350km, we transformed the slant TEC to the vertical TEC at the point that the line-of-sight direction to GPS satellite cut across the average height of the ionosphere. Because there is no dual frequency P-code GPS receiver in Korea, we used the data observed at the TAIW GPS station ($N25^{\circ},E121.5^{\circ}$) in Taiwan which is one of the core stations in International GPS and Geodynamics Services (IGS). The TEC values obtained in this work showed a typical daily variation of the ionosphere which is high in the daytime and low in the nighttime. Our results are found to be consistent with the SOLAR-DAILY data of NOAA and the Klobuchar's model for the ionospheric correction of GPS. In addition, in the cornparision with SOLAR-DAILY data, we estimated the precision of our TEC measurement as 2 TEC.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.4
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• pp.6-11
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• 2011

Launch of the first Quasi-Zentih Satellite System (QZSS) satellite, dubbed Michibiki, took place September 11, 2010 and technical and application verification of the satellite is being carried out. This paper presents the results obtained from processing of the L5 signal transmitted from the QZSS satellite. The QZSS L5 signal is collected in ETRI, Korea. And then, the acquisition and tracking are performed by the L5 software receiver implemented by ETRI. The tracking loop of FLL, PLL, and DLL, the EPL correlator output, and the C/No output results show that the QZSS L5 signal is normally processed. Finally, the paper demonstrates that the QZSS L5 signal could be used as GPS satellite based augmentation system in Korea as well as Japan.

• Journal of Advanced Navigation Technology
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• v.13 no.3
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• pp.319-326
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• 2009

In this paper, the key technologies of Navigation receiver for GNSS sensor station are presented as a development result of a GNSS ground station in ETRI. A wide-band antenna and RF/IF components and SW signal processing unit to cover the GPS and Galileo signals for GNSS receiver are developed and its performance is verified by using GPS live signal and GNSS RF signal simulator from SpirentTM. We also gather GIOVE-A signal by using H/W antenna and RF/IF units in IF-level as sampling frequency and bit number, 112MHz and 8bits, respectively by using the developed wide-band antenna and RF/IF components. Data acquisition is done by using commercial data acquisition device from National Instrument TM. The gathered data is fed into SW receiver to process Galileo E1 to verify Galileo signal processing by Galileo live signal from GIOVE-A.

• Korean Journal of Geomatics
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• v.5 no.1
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• pp.43-49
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• 2005

It is well known that GPS technique can be used for high accuracy leveling positioning if a precise geoid model is available to use at a surveying point. In this study, KOGD2003 geoid model was developed in and around Korean peninsula and this geoid model could be achieved by combining GPS/leveling data with the formerly developed KOGD2002. To this end, the software for orthometric height obtaining and geodetic datum transformation has been implemented with the visual C++ language, what we called GPS-GeoL v.1.0. In order to evaluate the performance and the accuracy of the software, GPS field tests were carried out in the Korean second-order leveling network over Chollabukdo area. Results of the tests have shown that the mean value of the differences between outputs of the software developed in this research and officially announced orthometric heights by NGII (National Geographic Information Institute) was 0.0221 m and also those of RMS was 0.0332 m. Therefore, it was possible to conclude that the KOGD2003 and GPS-GeoL v.1.0 software could be used to determine orthometric heights for civil construction field applications with cm-level accuracy.

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.90-101
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• 1995

We determined three dimensional precise WGS 84 corrdinates of two points in Bohyunsan Optical Astronomy Observatory using the GPS. One of the two points is the center on the top of pier for 1.8m telescope, and the other one is placed on the hill beside the dome of 1.8m telescope. We performed the simultaneous GPS observation at the KAO GPS station and Bohyunsan Obervatory for 5 days from December 18 to 22, 1993. We employed three Trimble 4000SST receivers for these observations. The observed data were processed by TRIMVEC-PLUS software of Trimble with the MBPS method and the Triple Difference L1/L2 ION free technique. Through this research, we determined WGS 83 latitude, longitude and height of 1.8m telescope in Bohyunsan Optical Astronomy Observatory with the values of $36^{circ}9'53".1943N\pm0."0018,\;128^{circ}58'35".6829E\pm0."0029,\;1162.47m\pm0.04m$, respectively.