• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2443-2449
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• 2014

The recent increase in the number of network RTK users has led to a longer wait time for connecting to the existing VRS service, and consequently caused inconvenience such as a longer turnaround time for surveys. To resolve such issue, the NGII has developed the FKP service that involves a one-way communication. However, it is not spreading across the market as fast as anticipated, due to accuracy problems in the field. This study uses eight unified control points for a reliability assessment to compare and analyze the survey results obtained through the VRS and FKP services in various ways. The analysis reveals that the standard deviation of the FKP service is ${\pm}0.02m$, which is two times larger than that of the VRS, whilst its standard errors are X:-0.025m and Y:0.011m, proving that it is reliable to be used in the field. Therefore, we expect that the FKP service is going to be more broadly utilized for field surveys in the future.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.1 s.28
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• pp.55-62
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• 2004

More recently, multiple reference based RTK GPS techniques(VRS ; Virtual Reference System) are becoming increasingly important for many precise GPS applications in many countries to overcome the constrained distance limitations of standard RTK systems. The precision of the position solutions of the rover receiver is closely connected with that of the corresponding virtual reference points(VRPs). The objective of this paper is to investigate the accuracy and performance of the VRPs on the test network have been made in post mode, and the overall analysis results were presented by comparing the solutions for the VRPs from the existing GPS reference station with the true values of the coordinates used to produce the observation data. The results show the reasonable accuracies of VRPs in the network area by using the VRS concept in post mode.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.2 s.29
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• pp.29-35
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• 2004

The plenty of availability and high precision of GPS CORS is the reason why it become important more and more in the fields of surveying widely. In this study, I extracted the arbitrary point's coordinate which is using GPS CORS data, now served in RINEX FORMAT via Inter-Net, with observation network of the existing triangulation and GPS CORS data. Then, with this arbitrary point as reference station RTK GPS was performed. And I will study VRS-GPS concept which reduces the time and cost in the fields of surveying.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_1
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• pp.463-469
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• 2013

In addition to the VRS-RTK service, FKP-RTK service launched recently in Korea however unlike VRS, it is not yet applied to various surveying tasks. VRS system is operated in two way communication over the mobile Internet. When user send rover position data to network RTK server and the server provides correction data to users continuously. It causes to increase communications load and makes delaying or failure in data transmission depends on server capacity and number of concurrent users. In contrast, since FKP system is one way communication system, user only receives correction data and area correction parameters for the selected Continuous Reference Station from the server. Thus, there is no limitation to the number of concurrent users in FKP system and it would be more efficient than VRS system in terms of economic. To this end, we performed FKP-RTK test for Unified Control Points and Urban Control Points where are located at 5 regions in Korea to evaluate the accuracy. As a result, almost of FKP positioning data are in error range of ${\pm}6.2cm$ in horizontal and it would be enough for construction survey such as for earth work in limited except precise structure survey.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.10a
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• pp.109-113
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• 2003

GPS 상시관측소의 활용과 중요성은 GPS측량에서 폭넓은 사용과 비교적 높은 정확도를 충족시키는 방안으로 점점 가치를 더 하고 있다. 현재 RINEX 포맷 형태로 인터넷 서비스를 하고 있는 GPS 상시관측소의 자료를 이용하여 기준점으로써의 가치를 평가하고 또한 시간과 경비를 줄일 수 있는 방법인 VRS-GPS기법을 연구하고자 한다. 본 연구에서는 임의의 기준국을 설치하여, 기존 삼각점과 GPS 상시관측소를 이용해 관측망을 형성, 그 결과를 비교 고찰하였으며 이 기준국을 RTK-GPS의 고정국으로 하여 실시간 측위를 하였다. 고정국은 전자 가상 기준국인 VRS-RTK 개념으로 가정하고 비교, 검증하였다.

• Journal of the Korean Association of Geographic Information Studies
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• v.25 no.4
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• pp.200-209
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• 2022

Providing real-time location information is emerging as a major goal of the national industry. In order to provide such real-time location information (3D spatial information), it is essential to develop a technology for a satellite positioning method. Therefore, the country continues to make efforts to increase satisfaction with the needs of consumers by introducing the Network RTK GNSS method. In this study, among the Network RKT GNSS(Global Navigation Satellite System) methods provided by the National Geographic Information Service, continuous observation and single observation were measured at the integrated reference point using VRS(Virtual Reference Station) and FKP(Flӓachen-Korrektur Parameter) to evaluate accuracy. In addition, we aim to maximize efficiency by presenting accuracy on the rapidly increasing Network RTK GNSS method in the field.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.174-182
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• 2014

To monitor the wind-induced responses of buildings, conventional real-time kinematic (RTK) methods based on two global positioning system (GPS) receivers (e.g., a reference and a rover) are widely applied. However, these methods can encounter problems such as difficulty in securing and maintaining a space for a reference station. With the recently developed virtual reference station (VRS)-RTK approach, the position of a structure can be measured using only a rover receiver. In this study, to evaluate the applicability of VRS-RTK methods in monitoring the lateral structural responses of frame structures, we performed free vibration tests on a one-story frame model (the first natural frequency of 1 Hz) and a three-story frame model (the first natural frequency of 0.85 Hz). To assess the reliability of the displacement and acceleration responses measured by the GPS, we performed a concurrent measurement using laser displacement sensors and an accelerometer. The accelerometer results were consistent with the GPS measurements in terms of the time history and frequency content. Furthermore, to derive an appropriate sampling rate for the continuous monitoring of buildings, the errors in the displacement responses were evaluated at different GPS sampling rates (5, 10, 20 Hz). The results indicate that as the sampling rate increased, the errors in the displacement responses decreased. In addition, in the three-story model, all modal components (first, second, and third modes) could be recorded at a sampling rate of 20 Hz.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.5
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• pp.469-479
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• 2014

N-RTK(Network based RTK) methods are able to improve the accuracy of GNSS positioning results through modelling of the distance-dependent error sources(i.e. primarily the ionospheric and tropospheric delays and orbit errors). In this study, the comparison of the TTFF(Time-To-Fix-First ambiguity), accuracy and discrepancies in horizontal/vertical components of N-RTK methods(VRS and FKP) with the static GNSS at 20 Unified Control Stations covering Incheon metropolitan city area during solar storms(Solar cycle 24 period) were performed. The results showed that the best method, compared with the statics GNSS survey, is the VRS, followed by the FKP, but vertical components of both VRS and FKP were approximately two times bigger than horizontal components. The reason for this is considered as the ionospheric scintillation because of irregularities in electron density, and the tropospheric scintillation because of fluctuations on the refractive index take the place. When the TTFF at each station for each technique used, VRS gave shorter initialization time than FKP. The possible reasons for this result might be the inherent differences in principles, errors in characteristics of different correction networks, interpolating errors of FKP parameters according to the non-linear variation of the dispersive and non-dispersive errors at rover when considering both domestic mobile communication infra and the standardized high-compact data format for N-RTK. Also, those test results revealed degradation of positing accuracy, long initialization time, and sudden re-initialization, but more failures to resolve ambiguity during space weather events caused by Sunspot activity and solar flares.

• Journal of The Geomorphological Association of Korea
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• v.19 no.2
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• pp.161-172
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• 2012

The Taeanhaean National Park is located on the middle of the west coast of Korean peninsula. Due to the relatively high wave energy, large tidal range which is about 7m, and extremely complex coastal line, various coastal land-forms such as mud-flats, sand beaches, sand dunes, sea cliffs etc. are well distributed in this area, and thus various coastal ecosystems are well preserved. However, because of reckless sand diggings and construction of artificial structures in the coastal zone, the natural flowing and exchange of coastal deposits were disturbed and the erosion in the beach and the dune has been seriously accelerated. To understand of the causes of these problems, we tried three times periodical measuring with VRS/RTK GPS instrument at the Hakampo and Anmyeon beach. According to seasonal changes of the coast-line, beach area and cross-section of study sites, generally erosion process was dominated in the summer and deposition process was followed after summer.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.4
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• pp.39-46
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• 2014

Network RTK GNSS positioning technique which has been developed to overcome the limitation of Single reference station RTK is used widely in the field of general surveying, cadastre surveying and engineering surveying due to the high accuracy and efficiency. It is specified Network RTK, Single reference station RTK and Static of GNSS as a surveying method in the regulation of Cadastre Re-survey Surveying. In this study, Network RTK and Static GNSS surveying were accomplished at cadastral re-survey field in Hadong, Gyeongnam and the surveying results were compared. Also, to analyze the performance of site calibration in Network RTK surveying, two types of Network RTK surveying with and without site calibration were accomplished and the results was compared. The research result shows that average positioning error between Network RTK(VRS) without site calibration and Static surveying result is 2.44cm and 1.53cm respectively and average positioning error between Network RTK(VRS) with site calibration and Static surveying result is 0.19cm and 0.82cm respectively at two zone. So, it was proved the effect of calibration in network RTK(VRS) surveying.