• The Journal of the Korea Contents Association
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• v.11 no.8
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• pp.51-58
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• 2011

This paper describes a development of system that enables the user to manage and display from 3D viewer after at real-time saves attribute informations in DBMS using RTK systems and 3D game engines. The 3-dimensional game engines for this system will be input a attribute values of underground utilities which is measured from RTK systems with wireless network. This system which sees does to make be a possibility of managing creation, elimination, modification for the underground utilities from 3-dimensional viewer. The coordinates about the underground utilities measures with GPS. The base reference point for RTK systems uses one in reference points which are measured in existing. GPS coordinates revised a reference point in standard. The 3-dimensional game engines are having the function which manages the underground utilities with 3-dimensions. The function is the same as wireless network of RTK systems, 3-dimensional display for terrain and underground utilities, input and registration for attribute of underground utilities, etc. The system which sees will be able to prevent the various accident which is caused by in the spatial location coordinate which underground utilities is inaccurate. And the system which sees is accurate is a possibility of managing and the application possibility is high very. Finally, this system could be applied very usefully from the point of view which starts a new town development.

• 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.1
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• pp.455-458
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• 2006

The Real Time Kinematic (RTK) technique is the most productive and accurate GPS positioning method today, as it can be determinate position within few centimeters instantly. This method is widely used for applications such as surveying, structure monitoring and machine guidance etc. In order to perform RTK processing for large scale systems (i.e. precise vehicle monitoring with many rovers), many expensive RTK receivers and same number of bidirectional communication units have to be installed to collect observation data communicate with the reference site and monitor its RTK solutions. Moreover, if applications require remote control or apply sensing instruments, we have to install computers at each rover. To limit expense and complexity of system management with a large number of rovers, we have developed server based RTK processing platform to share RTK function for all rovers. The system can be process many GPS stations with a single personal computer. we have also developed a specialized dual frequency GPS receiver unit without on-board RTK processing capability to reduce receiver cost in order to demonstrate the advantage of our server based RTK platform. This paper describes the concept of our server based RTK platform and specialized GPS receiver unit with existing applications in Japan.

• Journal of Positioning, Navigation, and Timing
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• v.3 no.3
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• pp.123-129
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• 2014

The real-time kinematic (RTK) is one of precise positioning methods using Global Positioning System (GPS) data. In the long baseline GPS RTK, the ionospheric and tropospheric delays are critical factors for the positioning accuracy. In this paper we present RTK algorithms for long baselines more than 100 km with estimating tropospheric delays. The state vector is estimated by the extended Kalman filter. We show the experimental results of GPS RTK for various baselines (162.10, 393.37, 582.29, and 1283.57 km) by using the Korea Astronomy and Space Science Institute GPS data and one International GNSS Service (IGS) reference station located in Japan. As a result, we present that long baseline GPS RTK can provide the accurate positioning for users less than few centimeters.

• Journal of Astronomy and Space Sciences
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• v.20 no.3
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• pp.197-204
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• 2003

We demonstrated positioning accuracy of iRTK system, which has been developed by Korea Astronomy Observatory, using a low-price GPS receiver. Each four different baseline positioning tests using the iRTK system, we certified 1-3 meters level positioning accuracy of the iRTK system. While the iRTK is similar to conventional RTK at coverage and accuracy, the iRTK positioning carried out from data processing center. And also, the iRTK system has no limit of data communication coverage because of using wire/wireless Internet. But the iRTK system has a weakness of short available coverage within 5km. Therefore we discussed a plan to adopt VRS (Virtual Reference System) as completion of the iRTK system preparing nation-wide iRTK service in near future.

• International Journal of Automotive Technology
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• v.8 no.5
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• pp.583-591
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• 2007

This paper describes the development of the $H_{\infty}$ lateral control system for an autonomous ground vehicle operating a limited area using the RTK-DGPS(Real Time Kinematic-Differential Global Positioning System). Before engaging in autonomous driving, map data are acquired by the RTK-DGPS and used to construct a reference trajectory. The navigation system contains the map data and computes the reference yaw angle of the vehicle using two consecutive position values. The yaw angle of the vehicle is controlled by the $H_{\infty}$ controller. A prototype of the autonomous vehicle by the navigation method has been developed, and the performance of the vehicle has been evaluated by experiment. The experimental results show that the $H_{\infty}$ controller and the RTK-DGPS based navigation system can sufficiently track the map at low speed. We expect that this navigation system can be made more accurate by incorporating additional sensors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.59-65
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• 2012

The study conducted the measurement of RTK-GPS with changing the number of observation as the method to differ reference stations of RTK-GPS. Also it aimed to suggest an effective application plan for cadastral surveying based on the accuracy analysis accordingly. According to the result of selecting the study region, observing with different reference stations, and comparing with previous TS performance, the 1st reference station was calculated as ${\pm}0.024m$ for x-coordinate's RMSE and ${\pm}0.029m$ for y-coordinate's RMSE, and the 2nd reference station was calculated as ${\pm}0.040m$ for x-coordinate's RMSE and ${\pm}0.029m$ for y-coordinate's RMSE. All these results (the 1st and the 2nd reference stations) are allowed as acceptable performance within the margin of error according to the existing cadastral regulations, and there was no significant difference between two performances. Therefore, unless there was no problem in receiving GPS satellite data, it would be possible to secure stable performance enough with 1 observation. Depending on surveying environment that has possible problems in receiving data, however, 2 or more observations would be necessary to secure stable performance.

• Journal of Navigation and Port Research
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• v.39 no.6
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• pp.479-484
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• 2015

Network RTK is a precise positioning technique using carrier phase correction data from reference stations within the network, and is constantly being researched for improved performance. However, the study for the system accuracy has been performed but system integrity research has not been done as much as system accuracy, because network RTK has been mainly used on surveying for static or kinematic positioning. In this paper, adequate monitoring system for network RTK is designed as basis research for integrity monitoring on network RTK. To this, fault tree on network RTK is analyzed, and a countermeasure is prepared to detect and identify the each fault items. Based these algorithms, monitoring system to use on central processing facility is designed for network RTK service.

• Journal of Advanced Navigation Technology
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• v.17 no.4
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• pp.404-412
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• 2013

Network RTK is widely used especially for static applications so far, however, the demand for high accuracy positioning for kinetic users such as land vehicles is growing for safety and convenience reasons. Kinematic users move along the roads and the network where they receive corrections can be changed. Compact Network RTK corrections should keep consistency while network change. In this paper, we introduced a method of generating Compact Network RTK corrections considering network ambiguity level adjustment by formulation of corrections. We verified the proposed method for reference station networks across whole country. We also generated Compact Network RTK corrections using simulation and real GPS data from reference stations in South Korea and evaluated performance of users. As a result, the discontinuity between corrections from two networks reduced to 0.25 cycle from several cycles. And user could achieve less than 8 cm (2DRMS) horizontal position accuracy continuously regardless of network change.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.295-305
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• 2018

Network RTK is a highly practical technology that can provide high positioning accuracy at levels between cm~dm regardless of user location in the network by extending the available range of RTK using reference station network. In particular, unlike other carrier-based positioning techniques such as PPP, users are able to acquire high-accuracy positions within a short initialization time of a few or tens of seconds, which increases its value as a future navigation system. However, corrections must be continuously received to maintain a high level of positioning accuracy, and when a time delay of more than 30 seconds occurs, the accuracy may be reduced to the code-based positioning level of meters. In case of SSR, which is currently in the process of standardization for PPP service, the corrections by each error source are transmitted in different transmission intervals, and the rate of change of each correction is transmitted together to compensate the time delay. Using these features of SSR correction is expected to reduce the performance degradation even if users do not receive the network RTK corrections for more than 30 seconds. In this paper, the simulation data were generated from 5 domestic reference stations in Gunwi, Yeongdoek, Daegu, Gimcheon, and Yecheon, and the network RTK and SSR corrections were generated for the corresponding data and applied to the simulation data from Cheongsong reference station, assumed as the user. As a result of the experiment assuming 30 seconds of missing data, the positioning performance compensating for time delay by SSR was analyzed to be horizontal RMS (about 5 cm) and vertical RMS (about 8 cm), and the 95% error was 8.7 cm horizontal and 1cm vertical. This is a significant amount when compared to the horizontal and vertical RMS of 0.3 cm and 0.6 cm, respectively, for Network RTK without time delay for the same data, but is considerably smaller compared to the 0.5 ~ 1 m accuracy level of DGPS or SBAS. Therefore, maintaining Network RTK mode using SSR rather than switching to code-based DGPS or SBAS mode due to failure to receive the network RTK corrections for 30 seconds is considered to be favorable in terms of maintaining position accuracy and recovering performance by quickly resolving the integer ambiguity when the communication channel is recovered.