• 한국도로학회논문집
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• 제15권1호
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• pp.155-161
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• 2013

PURPOSES: This study is to develop a road traffic sign recognition and automatic positioning for road facility management. METHODS: In this study, we installed the GPS, IMU, DMI, camera, laser sensor on the van and surveyed the car position, fore-sight image, point cloud of traffic signs. To insert automatic position of traffic sign, the automatic traffic sign recognition S/W developed and it can log the traffic sign type and approximate position, this study suggests a methodology to transform the laser point-cloud to the map coordinate system with the 3D axis rotation algorithm. RESULTS: Result show that on a clear day, traffic sign recognition ratio is 92.98%, and on cloudy day recognition ratio is 80.58%. To insert exact traffic sign position. This study examined the point difference with the road surveying results. The result RMSE is 0.227m and average is 1.51m which is the GPS positioning error. Including these error we can insert the traffic sign position within 1.51m CONCLUSIONS: As a result of this study, we can automatically survey the traffic sign type, position data of the traffic sign position error and analysis the road safety, speed limit consistency, which can be used in traffic sign DB.

• 한국위성정보통신학회논문지
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• 제10권4호
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• pp.46-51
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• 2015

본 논문에서는 항재밍 GPS(Global Positioning System) 시스템을 위한 선형 어레이 안테나(linear array antenna) 시뮬레이터(simulator)를 설계하고 시뮬레이션을 통해 다양한 성능 평가를 수행하였다. 먼저 GPS 위성의 신호 구조 분석을 통해 모의 송신신호를 발생시키고, 선형 어레이 안테나 고려시 잡음 환경하에서의 어레이 수에 따른 SNR(Signal to Noise power Ratio) 성능을 분석하였다. 또한 MMSE(Minimum Mean Square Error) 방식의 신호처리 시스템을 통해 재머(jammer) 수에 따른 항재밍 빔패턴(beam pattern) 성능을 분석하였으며, 안테나 칼리브레이션(calibration) 문제를 고려하여 어레이간 지연이 존재하는 경우에서의 항재밍 성능을 분석하였다.

• 한국측량학회지
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• 제26권6호
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• pp.617-624
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• 2008

일반적으로 단일기준국을 이용하는 실시간 동적(Real Time Kinematic) GPS는 무선모뎀을 통해 반송파 오차보정량을 이동국으로 전송하여 현장에서 바로 고정밀의 위치를 결정할 수 있다. 하지만 단일기준국 방식은 각 위성마다의 시간대별 반송파 측정값을 지속적으로 제공해야 하며, 전송장해와 모뎀간의 거리 따른 증가 등으로 위치정확도가 저하되는 단점이 있다. 본 논문은 이러한 단점을 보완하기 위해 3대 이상의 다중기준국을 활용한 네트워크 기반의 GPS 반송파 상대측위기술을 구현하였으며, Visual C++로 제작된 실시간 모니터링 프로그램을 이용하여 RTK 네트워크를 구성하였다. 네트워크 구성에서 얻어지는 다중기준국의 오차보정량 가운데 최적의 값을 자동으로 선택하고, GPS buoy 이동국에 적용하여 해수면 관측을 수행하였으며, 이를 통해 얻어진 해수면 변동량을 단일기준국과 비교, 분석하여 결과를 도출하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.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.

• 한국군사과학기술학회지
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• 제11권4호
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• pp.116-123
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• 2008

In this paper we study the performance of the measurement time-delay estimation of tightly-coupled GPS/INS(Global positioning system/Inertial Navigation system) system. Generally, the heading error estimation performance of loosely-coupled GPS/INS system using GPS's Navigation Solution is poor. In the case of tightly-coupled GPS/INS system using pseudo-range and pseudo-range rate, the heading error estimation performance is better. However, the time-delay error on the measurement(pseudo-range rate) make the heading error estimation performance degraded. So that, we propose the time-delay model on the measurement and compose the time-delay estimator. And we confirm that the heading error estimation performance in the case of measurement time-delay existence is similar with the case of no-delay by Monte-Carlo simulation.

• Journal of Positioning, Navigation, and Timing
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• 제13권3호
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• pp.341-353
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• 2024

This paper presents the design results of a Multi-band Global Positioning System (GPS)/Korean Positioning System (KPS) Real-Time Kinematics (RTK) precise positioning simulator and evaluate its functionalities. The designed simulator consists of a trajectory generation module, a Radio Frequency (RF) signal generation module, a RF signal reception module, a coarse positioning module, a precise positioning module, and an error statistics reporting module. Simulations in realistic scenarios confirm that the proposed baseband simulator works appropriately. The developed simulator can adjust the type, number, band, and Pseudo Random Noise (PRN) code type of the satellite constellation in various ways, and the practical positioning performance can be tested. It can also reflect the channel influence at the actual RF stage and the influence during the initial synchronization and tracking process. Considering such advantages, the proposed simulator would be useful in future researches and developments related to KPS.

• 제어로봇시스템학회논문지
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• 제4권2호
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• pp.220-225
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• 1998

In GPS (Global Positioning System) positioning, various measures can be used to select satellites or to evaluate the positioning results. Among these, GDOP (Geometric Dilution of Precision) and RGDOP (Relative GDOP) are the most frequently used. Although these measures are frequently used, the relationship between them is not clearly known. Moreover, the condition number is used as a traditional measure of numerical stability in solving linear equations. Sometimes, the volume of a tetrahedon made by the line of sight vector is used for simplicity. All of these measures share some common properties as well as differences. The relationships between these measures are analyzed in this paper.

• 한국측량학회지
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• 제24권2호
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• pp.167-173
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• 2006

전리층은 안테나에서 수신되는 GPS 신호에 가장 큰 오차를 유발시킨다. 이중 주파수(L1,L2)를 모두 사용하는 수신기는 두 주파수의 선형조합을 통해 전리층의 오차를 효율적으로 제거할 수 있지만, 단일 주파수 수신기(L1)는 전리층 모델을 이용하여 오차를 계산해야 한다. 본 연구에서는 한국천문연구원에서 운영하는 9개의 GPS 기준국 망 데이터를 이용하여 위 경도 각각 $1^{\circ}{\times}1^{\circ}$의 공간 해상도를 갖는 격자 기반의 새로운 전리층 모델을 개발하였고, 매 관측 시간대별로 한반도 상공의 총전자수(Total Electron Contents, TEC)를 계산하였다. 기존의 Klobuchar 모델과 새롭게 개발된 KASI 전리층 모델에 의한 측위 결과를 서로 비교하였고, 전리층의 총전자수 변화에 따른 모델의 정밀도를 제시하였다.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.141-148
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• 2023

In this paper, impacts of tropospheric delay gradient correction on PPP positioning performance were analyzed. A correction for tropospheric delay error due to the gradient was created and applied using external data, and reference station data were collected on a sunny day and a rainy day to analyze the GPS only dual-frequency PPP positioning results. As a result, on the sunny day, the convergence time was about 35 minutes and the final 3D position error was 10 cm, regardless of whether the correction for the tropospheric delay error by the gradient was applied. On the other hand, on the rainy day, the 3D position error converges only when the correction was applied, and the convergence time was about 34 minutes. Furthermore, the final 3D position error was improved from 30 cm to 10 cm. In addition, the analysis of the PPP by reference station location on the rainy day showed that the PPP positioning performance was improved when the correction was applied to a user located in an area where the weather changes.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.178-181
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• 2005

The positioning accuracy of the Global Positioning System (GPS) has been improved considerably during the past two decades. The main error sources such as ionospheric refraction, orbital uncertainty, antenna phase center variation, signal multipath, and tropospheric delay have been reduced substantially, if not eliminated. In this study, the GPS data collected by the GPS receivers that were established as continuously operating reference stations by International GNSS Service (IGS), Ministry of the Interior (MOl), Central Weather Bureau (CWB), and Industrial Technology Research Institute (ITRI) Of Taiwan are utilized to investigate the impact of atmospheric water vapor on GPS positioning determination. The surface meteorological measurements that were concurrently acquired by instruments co-located with the GPS receivers include temperature, pressure and humidity data. To obtain the influence of the GPS height on the proposed impact study. A hydrodynamic ocean tide model (GOTOO.2 model) and solid earth tide were used to improve the GPS height. The surface meteorological data (pressure, temperature and humidity) were introduced to the data processing with 24 troposphere parameters. The results from the studies associated with different GPS height were compared for the cases with and without a priori knowledge of surface meteorological measurements. The finding based on the measurements in 2003 is that the surface meteorological measurements have an impact on the GPS height. The associated daily maximum of the differences is 1.07 cm for the KDNM station. The impact is reduced due to smoothing when the average of the GPS height for the whole year is considered.