• 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.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.251-254
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• 2006

A precise real-time method of using the IGS ultra rapid products (IGU) and the GPS broadcast ephemeris to calculate the VRS orbit corrections was presented here which was suited for GPS/VRS reference station network based positioning. Test data acquired from both the SGRSN (Sichuan GPS Reference Station Network) and SCIGN (Southern California integrated GPS network) were used to evaluate the performance of the modeling techniques. The new method was proven to be more precise and reliable compared with the existing conventional network-based orbit error interpolation method. It was shown that 0.004ppm relative accuracy was reached, namely the influence from the orbit bias for the RTK positioning within 100km area can be of sub-millimeter level.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.471-480
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• 2018

Accurate target coordinate is very important in military operations especially field artillery's ground-to-ground attack and air-force's air-to-ground attack. DOS(or TAS) is used to acquire target coordinates from long distance. DOS is comprised of LRF and goniometer. LRF measures distance between DOS and target. Goniometer is comprised of azimuth and vertical angular sensors, DMC and internal GPS receiver. DOS must set the position and orientation(finding grid north) before measurement step(target coordinate acquisition). To improve accuracy of target coordinate, VRS RTK and reference point method are proposed in DOS setup step. VRS RTK provides accurate location coordinate with small deviations, providing high accuracy and precision in positioning and orientation. As a result, horizontal coordinate(easting and northing) accuracy is improved from 2.68 mil(C.L. = 0.95) mil to 0.58 mil(C.L. = 0.95).

• Spatial Information Research
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• v.18 no.5
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• pp.1-11
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• 2010

Since January 2009, Seoul Metro Government(SMG) is operating own Network RTK Systems connecting four(4) GNSS Reference Stations which are installed inside Seoul Metro City area. SMG is currently providing VRS data service via wireless internet for Network-RTK and RINEX data observed from GNSS Reference Stations. This paper will discuss utilization of data available from SMG Network-RTK System for various applications, and present the test results on practicalities of Virtual RINEX data. For the utilization of data available from SMG Network- RTK system, 1)NTRIP data delivery of GNSS realtime observables streaming and converting to RINEX at receiving side, 2) monitoring deformation of bulky structures using GNSS observation were discussed. In addition to those discussion, 3) broadcasting VRS correction data for job site via radio modem after acquiring such correction data on-line using NTRIP based GNSS Internet Radio from SMG Network-RTK System were introduced. For the test results on practicalities of Virtual RINEX data, 1) the post-processing results of the GNSS observation data on a certain point with GNSS Reference Station data have been compared to the post-processing results of Virtual RINEX data on the same point generated from SMG Network-RTK System, and 2) VRS RTK positioning results for a certain point and post-processing results of Virtual RINEX data for the point were compared. The results showed only a few mm difference, and the high possibility for using Virtual RINEX data for post-processing applications.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.91-96
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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 for static positioning in post processing mode. For this, some VRPs at the inside and outside of test network have made in post mode, and the overall analysis results were presented by comparing the solution for the VRPs from the existed 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.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.28-28
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• 2003

한국천문연구원이 개발한 iRTK(inverted Real Time Kinemtic) 시스템의 성능을 분석하고 개선방향에 대해 논의하였다. 제안하는 iRTK 시스템은 기존의 실시간 고정밀 측위기법인 RTK와 측위방법과 적용범위 면에서 유사하지만, 중앙에서 일괄적으로 사용자의 위치를 계산하고 유무선 인터넷을 이용하므로 통신범위에 제약을 받지 않는 장점이 있다. iRTK 시스템의 성능분석은 소요시간, 성공률, 정확도를 판단기준으로 하여 이루어졌으며 측정점에서는 중저가의 GPS 수신기를 사용하였다. 분석결과 기준점과의 기선거리 5km 이내에서 1-3m 수준의 측위정밀도를 얻을 수 있었으며, 측위성공률은 최적의 측정시간을 이용할 경우 약 90% 수준이었다. 이를 통해 iRTK 시스템의 적용가능 분야를 살펴보고 적용범위와 정밀도 개선을 위한 몇 가지 개선사항을 검토하였다. 이 중 VRS(Virtual Reference System)는 iRTK 시스템의 성능을 개선하고 단점을 보완할 수 있는 대안으로 검토되었으며, iRTK+VRS 시스템 구축의 가능성에 대해 논의하였다.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.67-73
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• 2021

The need for precise location data is growing across numerous markets, and so is the number of affordable high-precision GPS receivers. In this paper, we validated the performance of RTAP2U, a low-cost high-precision RTK receiver that was recently released. Two positioning modes were tested: static and driving. The static test conducted Zero-Baseline Single-RTK and Network-RTK survey for 57 hours and 51 hours, respectively. For the driving test, Network-RTK survey was conducted using VRS services provided by NGII based on Trimble PIVOT and Geo++ GNSMART. The static test showed about 1 cm horizontal and vertical accuracies, which is very stable considering the test duration longer than 50 hours. The integer ambiguity FIX rate marked a solid 100%. The driving test result also reached a 100% FIX rate. Horizontal and vertical accuracies were better than 2 cm and 3 cm, respectively. Researchers can refer to this paper when considering affordable high-precision GPS receivers as an option.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.3
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• pp.31-39
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• 2015

This paper presents the static and kinematic positioning accuracy by the real-time GPS positioning modes of the low-cost GPS receivers using NTRIP-based augmentation service. For this, acquires both the raw measurements data of the field tests by LEA 6T GPS module of u-blox AG, and correction communication via NTRIP caster with RTKLIB as an open source program for GNSS solution. With computing the positions of the check points and road tracks by six kinds of GPS positioning modes which are Single, SBAS, DGPS, PPP, RTK, and TCP/IP_RTK, compared these results to the reference position of the check points. The position error average and rmse of the static test by GPS L1 RTK surveying showed $N=0.002m{\pm}0.001m$, $E=0.004m{\pm}0.001m$ in horizontal plane, and $h=-0.116m{\pm}0.003m$ in vertical, these results are very closed to the coordinates with the geodetic receiver. Especially, in case of the kinematic test with obstacles located on both sides of road, the computed track with ambiguity fixing showed very similar trajectory considerably from VRS network RTK mode. And also, evaluate and verify the performance of the TCP/IP_RTK mode developed based on TCP/IP protocol.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.4
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• pp.413-422
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• 2012

After development of GPS in the 1960's, the United States released SA(Selective Availability) in 2000 and then the GPS has become commercialized to the present. The result of repeatedly developed GPS observation, the GPS real-time observation methods is RTK which basically always needs two base stations and has a fault of the accuracy decreasing as the distance between a mobile station and a receiver is increasing. Because of these weakness, VRS method has come out. VRS(Virtual Reference Station) generates the imaginary point near mobile station from several observatory datum of GPS, sets the accurate location of mobile station, thus shows high reliability and mobility. Now, the cadastral datum point is used with azimuth, repetition, and graphical traversing method for traverse network. The result of measurement indicates many problems because of different accomplishment interval given point, restrictions on the length of the conductor, many errors on the observations. So, this study did comparative analysis of the cadastral datum points through VRS method by Continuously Operating Reference Station. Through the above comparative analysis, The comparative result between surveyed result with repetition method through total station observed Cadastral Control Points and surveyed result with VRS-RTK has shown that average error of x-axis is -0.08m, average error of y-axis, +0.07m and average distance error is +0.11m.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.2
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• pp.21-28
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• 2010

The classical RTK System requires that GPS data is transmitted from a single reference receiver to one or more roving units. But its error increase due to distance between reference and rover. VRS(Virtual Reference Station) system, a network of reference stations can be used to isolate the components of these systematic errors and use the resultant corrections to create Virtual Reference Stations at any location within the network. Use of a VRS significantly reduces the effects of systematic errors and improved accuracy. In this study, Network-RTK survey using VRS serviced by NGII(National Geographic Information Institute) was performed and the results were compared with results of total station surveying and notified coordinates of cadastral control points for utilization assessment of VRS.