• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.3
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• pp.301-308
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• 2001

Nowadays GPS play a important roles in the navigation system of vehicles, but, it doesn't determine the kinematic positions of vehicles accurately because of few satellites in the urban canyon covered with trees and high buildings. So GLONASS (GLObal Navigation Satellites System), the Russian satellites'system, operated in 1996, was introduced to overcome this drawbacks. Therefore, this study deals with the kinematic positioning of vehicles with Real-time code differential positioning methods. As a result, Real-time DGPS/GLONASS is better than Real-time DGPS in the differential corrected positions and HDOP (Horizontal Dilution of Precision). And it was shown that the combined GPS/GLONASS contributes to the precise kinematic positioning of vehicles.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.2 s.20
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• pp.87-95
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• 2002

Real-time Kinematic GPS enables high accuracy Positioning by real time. If ambiguity use an integer solution, can obtain accuracy of several 'mm', and can obtain accuracy of tens 'em' if use real solution. In this study, We accomplish surveying by existent traditional surveying techniques (Total Station), Static GPS techniques and RTK-GPS techniques by Field Calibration about uniformity measuring point and then compared and ana1yzed each techniques positioning accuracy etc.. Result that achieve by Static-GPS in Plane area, about all measuring points, expressed error fewer than 3cm. Result that achieve RTK-GPS Surveying by Field Calibration in Plane area, could know that RTK-GPS techniques by Field Calibration is available in Plane area because expressing errors fewer than all 6cm, except case that do not get fixed solution of ambiguity Field Calibration RTK-GPS could know economically than existent conventional type measurement and existent GPS's measurement techniques that efficiency is very high.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.3
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• pp.263-272
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• 2001

For a high resolution real-time kinematic GPS surveying using carrier phase, positioning accuracy according to the OTF initialization was better than 1 cm with more than 5-minute initialization within 20 km baseline. Also, it is recommended that measurements be carried out when PDOP and RDOP can be kept less than 4.0 since the geometrical layout of satellites has a great influence on the positioning accuracy. After considering the initial conditions and measuring time zone for real-time kinematic GPS. post-processed continuous kinematic GPS and real-time kinematic GPS measurements have been carried out. A new system has been proposed to store measured data by using a program developed to store GPS data in real time and to monitor the satellite condition through controller at the time of measurement. As a result, it has been revealed that possible noise in surveying could be corrected and the accuracy could be improved.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.3
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• pp.217-223
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• 2004

In order to improve real-time positioning accuracy, a number of methods have been tested and one of those is the inverted RTK(Real-time kinematic) that gives a precise positioning by handling carrier phase measurements. For the inverted RTK positioning, it needs the L1 phase measurement at least for 1～2 minutes and the additional reference stations/communication system and a data processing server are required. The L1 code and carrier phase measurements for real-time application are used simultaneously and then Kalman filter is applied to estimate integer ambiguities. Double differenced integer ambiguities are resolved by utilizing the FARA(Fast Ambiguity Resolution Approach). In this paper, we propose the method to improve the positioning accuracy and performed the field tests for several baselines from DAEJ reference station in KAO(Korea Astronomy Observatory).

• Journal of Astronomy and Space Sciences
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• v.19 no.4
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• pp.377-384
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• 2002

We have developed Real-time Phase DAta processor(RPDAP) for GPS L1 carrie. And also, we tested the RPDAP's positioning accuracy compared with results of real time kinematic(RTK) positioning. While quality of the conventional L1 RTK positioning highly depend on receiving condition, the RPDAP can gives more stable positioning result because of different set of common GPS satellites, which searched by elevation mask angle and signal strength. In this paper, we demonstrated characteristics of the RPDAP compared with the L1 RTK technique. And we discussed several improvement ways to apply the RPDAP to precise real-time positioning using low-cost GPS receiver. With correcting the discussed weak points in new future, the RPDAP will be used in the field of precise real-time application, such as precise car navigation and precise personal location services.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.4
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• pp.389-396
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• 2012

As the demand on the precise positioning for the moving objects has been increased in the various industry field, many studies have been conducted to analyze real time kinematic technique and its practical usage. The main purpose of this study is to analyze the possibility of Network-RTK(VRS) in real-time kinematic positioning. So, the accuracy analysis has been conducted by comparing the Network-RTK(VRS) position with respect to the RTK position. As a result, Network-RTK(VRS) based on kinematic positioning has centimeter level of RMS in the ideal environment compared to RTK positioning. However, when the integer ambiguities was lost, the accuracy of Network-RTK was meter level. At that time, the quality value has been changed dramatically and shows big correlation with accuracy. When the position and height quality values are within 0.1m, the RMS of the horizontal and vertical position appears better than 10cm and 20cm, respectively. However, if the quality value is over 0.1m, the RMS increases to larger than a meter. Therefore, it is recommended to check the quality value when conducting Network-RTK(VRS) kinematic positioning to get the centimeter level accuracy.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.51-51
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• 2000

The ambiguity resolution is an essential task for the precise carrier phase differential GPS. In practice, however, there are still many problems in resolving the ambiguity in kinematic mode, especially in the urban areas. The multipath in received signal, the frequent change in visible satellites, and the cyclic slips make the ambiguity resolution very difficult task in real-time operation. In this paper, we consider a differential positioning with the float ambiguity that is free from the integer constraint. The float ambiguity estimation if carried out by the Kalman filter. The float and fixed ambiguities are combined together to determine the position in real-time kinematic mode.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.191-196
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• 2006

In GPS Positioning, the error of satellite orbit will affect user's position accuracy directly, it is important to determine the satellite orbit precise. The real-time orbit is needed in kinematic GPS positioning, the precise GPS orbit from IGS would be delayed long time, so orbit prediction is key to real-time kinematic positioning. We analyze the GPS predicted ephemeris, on the base of comparison of EKF and UKF, a new orbit prediction method is put forward based on UKF in this paper, the result shows that UKF improves the orbit predicted precision and stability. It offers a new method for others satellites orbit determination as Galileo, and so on.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.2
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• pp.79-86
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• 2017

Precise Point Positioning-Real Time Kinematic (PPP-RTK) refers to a technology that combines PPP with network-RTK in which a user does not directly receive observed data from a reference station but receives State-Space Representation (SSR) messages corrected for error components from a central processing station through Networked Transport of RTCM via Internet Protocol (NTRIP) or Digital Multimedia Broadcasting (DMB) for purposes of positioning. SSR messages, which refer to corrections used in PPP-RTK, are generated by a central processing station using real-time observed data collected from reference stations and account for corrections needed due to the ionosphere, troposphere, satellite orbital errors, satellite time offsets, and satellite biases. This study used a type of SSR message provided in South Korea, known as Korea-SSR (K-SSR), to implement a PPP-RTK algorithm based on code-pseudorange measurements and validated its accuracy within the reference station network. In order to validate the accuracy of the implemented algorithm outside of the network, the K-SSR was extrapolated and applied to positioning in reference stations in Changchun, China (CHAN) and Japan (AIRA). This also entailed a quantitative evaluation that measured improvements in accuracy in comparison with point positioning. The results of the study showed that positioning applied with extrapolated K-SSR correction data was more accurate in both AIRA and CHAN than point positioning with improvements of approximately 20~50%.

• Journal of Positioning, Navigation, and Timing
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• v.2 no.1
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• pp.19-31
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• 2013

It is well known that the accident of vehicles carrying hazardous materials incurs huge losses economically and socially. To detect and respond rapidly against the accident of a vehicle carrying hazardous materials, it is essential to estimate the relative navigation information between the forward tractor module and the backward trailer module of the vehicle reliably and accurately. In this paper, a precise relative positioning system based on GPS is designed, implemented, and evaluated as a prerequisite to design an effective relative navigation system for the vehicle carrying hazardous materials. An experiment using field-collected 10 Hz real GPS measurements showed that the designed relative positioning system achieves 22 cm accuracy within 15 epochs by float solutions. Also, it was found that cm-level integer solutions can be generated reliably after the quick convergence of float solutions.