• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.6
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• pp.505-510
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• 2013

In order to detect and identify the GPS clock anomaly in the Differential GPS real environment, this paper addresses a method for minimizing the measurement noise of reference receivers. It estimates the real measurement noise that removed the uncommon error source from pseudorange measurement to minimize the measurement noise. Based on the output of two reference receivers, it first removes the uncommon errors, then optimizes the measurement noise by applying the correction data. Finally, it detects and identifies the satellite clock anomaly using the minimized measurement noise. The method will increase the availability of current DGPS reference system.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.268-269
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• 2015

National Maritime PNT Office is operating 17 DGPS reference sites. Considering the relatively small size of South Korea, however, we thought that it is maintaining too many stations. For this reason, new algorithms were developed to effectively generate Pseudo-Range Corrections for the purpose of providing consistent DGPS accuracies throughout the country even with a minimum number of stations.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.328-333
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• 2012

Current differential GPS (DGPS) system consists of reference station (RS), integrity monitor (IM), and control station (CS). The RS computes the pseudorange corrections (PRC) and generates the RTCM messages for broadcasting. The IM receives the corrections from the RS broadcasting and verifies that the information is within tolerance. The CS performs realtime system status monitoring and control of the functional and performance parameters. The primary function of a DGPS integrity monitor is to verify the correction information and transmit feedback messages to the reference station. However, the current algorithms for integrity monitoring have the limitations of integrity monitor functions for satellite outage or anomalies. Therefore, this paper focuses on the detection and identification methods of satellite anomalies for maritime DGPS RSIM. Based on the function analysis of current DGPS RSIM, it first addresses the limitation of integrity monitoring functions for DGPS RSIM, and then proposes the detection and identification method of satellite anomalies. In addition, it simulates an actual GPS clock anomaly case using a GPS simulator to analyze the limitations of the integrity monitoring function. It presents the brief test results using the proposed methods for detection and identification of satellite anomalies.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.11a
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• pp.159-161
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• 2011

항만국통제제도는 기항지국별로 항만국통제를 시행하던 것이 지역별로 협력체제를 구축하여 기준미달선 제거를 위해 노력하게 되었다. 하지만 지역협력체제에 법적 구속력이 없어 한계성을 보이고 있으므로 조약화하는 것이 기준미달선을 제거하는 최선의 방법이 될 것이다. 지역협력체제 MOU는 실질적 구속력이 없어 한계성을 보이고 있으므로 강제화한다면 항만국통제 목적을 달성할 것이고 이것이 확대되면 범세계적으로 기준미달선은 제거되고 해상안전과 해양환경보호는 달성될 것이다.

• Journal of Advanced Navigation Technology
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• v.19 no.3
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• pp.207-216
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• 2015

Since the distribution of SBAS reference stations is one of the most important factors that affect the system performance, the effects of the distribution should be analyzed carefully from the beginning of the program to develop the system conforming to given performance requirements. The reference stations of KASS, the Korean SBAS, are planned to be installed only inside South Korea, which limits the number and area of those. It differentiates KASS from others that have much larger sites. In this paper, the author analyzes the performance impact on UDRE and ${\delta}UDRE$ for GPS and GEO due to the limitations by a series of simulations, which showed that the UDRE performance depends on the diversity of the reference station distribution and the impact on the GEO UDRE is significant. The paper concludes by providing KASS design and development considerations to minimize the possible performance risks due to the limitations of KASS reference station distribution.

• Proceedings of the KAIS Fall Conference
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• 2011.12a
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• pp.105-108
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• 2011

본 연구에서는 기준국을 달리함으로써 관측 횟수를 달리하여 RTK-GPS 측량을 시행하여 보고 이에대한 정확도 분석을 토대로 지적측량에 효율적인 적용 방안을 제시하여 보고자 하였다. 실험지역을 선정하고 기준국을 달리하여 관측 후 기존 TS 성과와 비교한 결과, 제1기준국은 X좌표의 RMSE가 ${\pm}0.024m$, Y좌표의 RMSE가 ${\pm}0.016m$로 산출되었고, 제2기준국은 X좌표의 RMSE가 ${\pm}0.040m$, Y좌표의 RMSE가 ${\pm}0.029m$로 산출되었다. 이는 모두 현행 지적법령에서 규정하고 있는 성과인정 범위 이내의 오차이고, 더불어 두 성과의 차이는 크지 않았다. 따라서 GPS 위성자료 수신에 장애가 없다면 1회 관측으로도 충분히 안정적인 성과의 취득이 가능한 것으로 나타났다. 다만, 측량 환경에 따라 주변에 수신에 제약을 받는 요소가 있다면 이러한 지역에 대해서는 성과의 안정적인 취득을 위해 2회 이상의 관측이 필요할 것으로 판단된다.

• Journal of Navigation and Port Research
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• v.33 no.6
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• pp.395-400
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• 2009

In order to prepare for the DGNSS recapitalization and implementation of the functions for software based reference station and integrity monitor (RSIM) system, this paper proposes a design of integrity monitor functions of maritime differential GPS RSIM. The most critical functions of the integrity monitor (IM) are to generate and send flags to the reference station (RS) along with system feedback. Firstly, it presents the architecture of software based RSIM, and analyzes the performance standard of integrity monitor for maritime DGPS reference station This paper then designs the functions of integrity monitor for DGPS reference station based on the performance standard. Finally, this paper presents the results of performance analysis for the functionality of integrity monitor using the GNSS simulator. it discusses the study method and its application for the system implementation.

• 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 the Korea Institute of Information and Communication Engineering
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• v.19 no.11
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• pp.2569-2575
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• 2015

Network RTK generally uses a linear interpolation method by using the corrections from reference stations. This minimizes the spatial decorrelation error caused by the increase of distance between the reference station's baseline and user's baseline. However, tropospheric delay, a function of the meteorological data can cause a spatial decorrelation characteristic among reference stations within a network by local meteorological difference. A non-linear characteristic of tropospheric delay can deteriorate Network RTK performance. In this paper, the modeling of tropospheric delay irregularity is made from the data when the typhoon is occurred. By using this modeling, analyzing the effect of meteorological difference between reference stations on correction is performed. Finally, we analyze an effect of non-linear characteristics of tropospheric delay among reference stations to Network RTK user.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.135-143
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• 2009

Integrating the Global Positioning System (GPS) and Inertial Navigation System (INS) sensor technologies using the precise GPS Carrier phase measurements is a methodology that has been widely applied in those application fields requiring accurate and reliable positioning and attitude determination; ranging from 'kinematic geodesy', to mobile mapping and imaging, to precise navigation. However, such integrated system may not fulfil the demanding performance requirements when the baseline length between reference and mobil user GPS receiver is grater than a few tens of kilometers. This is because their positioning/attitude determination is still very dependent on the errors of the GPS observations, so-called "baseline dependent errors". This limitation can be remedied by the integration of GPS and INS sensors, using multiple reference stations. Hence, in order to derive the GPS distance dependent errors, this research proposes measurement processing algorithms for multiple reference stations, such as a reference station ambiguity resolution procedure using linear combination techniques, a error estimation based on Kalman filter and a error interpolation. In addition, all the algorithms are evaluated by processing real observations and results are summarized in this paper.