• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.103-104
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• 2014

Wide Area Differential GNSS(WA-DGNSS) was developed in order to improve the accuracy and integrity performance of GNSS. In Korea, WA-DGNSS development project, which aims to develop core algorithms and verify the performance using pseudolite-based demo system, is currently in progress. In this paper, overall structure of developed system and experimental methods which enables the post-processing test with commercial receiver will be described. In this system, pseudolite is used to broadcast augmenting signal and RF signal logger and broadcaster were used to test the performance. Performance test was conducted broadcasting the logged RF signal and pseudolite signal to commercial receiver and those results will be described.

• Journal of Navigation and Port Research
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• v.37 no.4
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• pp.367-373
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• 2013

Wide area differential GNSS(WA-DGNSS) collects GPS measurements from the several reference stations and estimates 3-D satellite orbit error, satellite clock error, ionospheric delay. These correction messages are broadcasted to user, then user can have more accurate and reliable position estimates. The performance of WA-DGPS can be changed depending on the position of reference stations. To select proper reference stations, performance analysis with the change of reference stations is necessary. In this paper, changing the geographical location of reference stations, we carried out simulation based test and show the performance of WA-DGNSS in Korea.

• Journal of Advanced Navigation Technology
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• v.27 no.5
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• pp.510-518
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• 2023

This paper introduces a MATLAB graphical user interface (GUI) based software for performance analysis of navigation message and wide area differential correction of regional navigation satellite system (RNSS). This software was developed to analyze satellite orbit/clock-related performance of navigation message and wide area differential correction simulating RNSS for regions near Korea based on different distributions of monitor and reference stations. As a result of software operation, navigation message and wide area differential correction are given as output in MATLAB file format. From the analysis of output, it was confirmed that valid navigation message and wide area differential correction could be generated from the results about statistical feature of orbit and clock prediction errors, cm-level fitting errors for navigation message parameters, and 81.9% enhancement in range error for wide area differential correction.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.390-392
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• 2013

In the paper, design and implementation results of the reference station software are described for the WA-DGNSS that is currently developed in pseudo-realtime concept. The reference software is designed and implemented by applying the object oriented methodology.

• Journal of the Korean earth science society
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• v.31 no.1
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• pp.1-7
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• 2010

Many studies have successfully developed a number of terrain correction programs in gravity data. Furthermore, terrain data that is a basic data for terrain correction has widely been provided through internet. We have also developed our own precise gravity terrain correction program. The currently existing gravity terrain correction programs have been developed for regional scale gravity survey, thus a more precise gravity terrain correction program needs to be developed to correct terrain effect. This precise gravity terrain program can be applied on small size geologic targets, such as small scale underground resources or underground cavities. The multiquadric equation has been applied to create a mathematical terrain surface from basic terrain data. Users of this terrain correction program can put additional terrain data to make more precise terrain correction. In addition, height differences between terrain and base of gravity meter can be corrected in this program.

• Journal of Advanced Navigation Technology
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• v.11 no.4
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• pp.371-377
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• 2007

Ionospheric time delay is one of the main error source for single-frequency DGPS applications, including time transfer and Wide Area Differential GPS (WADGPS). Grid-based algorithm was already developed for WADGPS but that algorithm is not applicable to geomagnetic storm condition in accuracy and management. In geomagnetic storm condition, the spatial distribution of vertical ionospheric delay is noisy and therefore the accuracy of modeling become low in grid-based algorithm. For better accuracy, function based algorithm can be used but the continuity of correction message is not guranteed. In this paper, we propose the ionospheric model using wavelet based algorithm. This algorithm shows better accuracy with the same number of correction message than the existing spherical harmonics algorithm and guarantees the continuity of correction messages when the number of message is expanded for geomagnetic storm condition.

• Journal of Korean Society for Geospatial Information Science
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• v.14 no.3 s.37
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• pp.71-77
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• 2006

MSAS satellite is the geostationary satellite for realizing WADGPS that can get the position of moving object in a wide area receiving the correction signal created from a ground using satellite. In this study, we analyzed two different data. One is using the correction signal transmitted from MTSAT-2 satellite of MSAS and the other is receiving the data of DGPS using BEACON receiver. As we compared both data, we could get the conclusion that the position accuracy of both data is also can get up to the standard or the conventional real-time code DGPS. As a result, we can expect that if we use MTSAT-2 satellite and BEACON receiver together, we can apply them LBS part that require real-time data or the obtaining geospatial information that does not require high accuracy much regardless of topography.

• Journal of Korean Society for Geospatial Information Science
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• v.19 no.3
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• pp.75-82
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• 2011

In this study, author analyzed the overview and the convergence time of Fixed solutions (<15cm) of OmniSTAR, one of SBAS(Satellite Based Augmentation System) as WADGPS (Wide Area Differential GPS), which can compensate the drawbacks of the existed GNSS (Global Navigation Satellite System) that require the expensive receiver and is impossible to position in case of the radio interference in urban sometimes. As a result, the test shows that the less than 15cm 3D standard deviation converges in 39 minutes at Dynamic mode and 28 minutes at Static mode. It is expected that we can apply OmniSTAR to a variety of fields such as LBS(Location Based Service), mobile positioning, and the geo-spatial information industry that does not necessarily guarantee the high position accuracy.

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.319-322
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• 2006

2002년 5월 촬영이 시작된 SPOTS 영상은 공간해상도가 2.5mX2.5m로 고해상도이면서도 촬영폭이 광역적이어서 다양한 활용이 가능하다. SPOT5영상을 보다 유용하게 활용하기 위해서는 단순 기하보정 보다는 높은 정확도를 얻을 수 있는 정사보정이 요구된다. 보정영상의 정확도에 영향을 미치는 요소로는 지형, GCP, DEM등이 있다. 본 연구에서는 다른 조건들은 동일하게 하고, 자료 구축에 많은 시간이 소요되는 DEM(수치표고모델)의 축척만을 달리하여 보정 영상의 정확도를 비교하였다. 그 결과 DEM의 축척 변화가 보정 영상에 미치는 영향은 미비한 것으로 나타났다. 따라서 작업의 효율성을 고려할 경우에 소축척의 DEM을 사용하는 것이 바람직하다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2601-2610
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• 2013

The main limiting factors of Precise Point Positioning(PPP) accuracy are errors in broadcast satellite orbits, clock errors, and the others, which are receiver-dependent errors(ionospheric, tropospheric refraction, multipath, and tides, etc.). Therefore, to facilitate high precision PPP, precise orbits/clocks corrections, the receiver-dependent errors corrections have to apply to multi frequency GNSS measurements for an ionosphere free combination and integer ambiguity resolution in real-time. Currently, there are many Analysis Centers, which offer the precise corrections stream computed in real-time using the global or regional GNSS tracking network. The goles of this research considered performances of the real-time static PPP with using RTCM corrections from NTRIP casters. For this, the corrections streams of Analysis Centers received via NTRIP does apply to GNSS data of check points individually, as well as jointly, in accordance with various session lengths. After that, have compared the PPP results from the corrections streams with each other, and with Standard Point Positioning(SPP) results.