• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.418-426
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• 2022

Unlike OSR(observation space representation), the SSR(state space representation) augmentation system is suitable for a one-way broadcasting service because it provides the same corrections to all users in the service area. Due to this advantage, several GNSS(global navigation system) systems such as Galileo, BDS(beidou navigation satellite system), QZSS(quasi zenith satellite system) are establishing PPP (precise point positioning)/PPP-RTK precision positioning services based on SSR messages. Therefore, in this paper, we try to understand the trends of satellite-based PPP/PPP-RTK correction services by analyzing the system configurations, characteristics, and precise positioning performance of satellite-based SSR correction broadcasting services.

• KIISE Transactions on Computing Practices
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• v.23 no.3
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• pp.148-155
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• 2017

In this paper, we develop a new system to estimate the step count for a smartphone user. The system analyzes data obtained from the accelerometer, magnetic sensor, and gyroscope of an android smartphone to extract pattern information of human steps. We conduct an experiment and evaluation to confirm that the proposed system successfully estimates the number of steps with 96% accuracy when hand-held and 95.5% accuracy when in-pocket. In addition, we found that detection errors were caused by human motions such as touching the screen, shaking the device up and down, sitting up and sitting down, and waving the phone around.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.2
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• pp.247-258
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• 2003

In this paper, we present a pen-shaped input device equipped with accelerometers and gyroscopes that measure inertial movements when a user writes on 2 or 3 dimensional space with the pen. The measurements from gyroscope are integrated once to find the attitude of the system and are used to compensate gravitational effect in the accelerations. Further, the compensated accelerations are integrated twice to yield the position of the system, whose basic concept stems from the field of inertial navigation. However, the accuracy of the position measurement significantly deteriorates with time due to the integrations involved in recovering the handwriting trajectory This problem is common in the inertial navigation system and is usually solved by the periodic or aperiodic calibration of the system with external reference sources or other information in the filed of inertial navigation. In the presented paper, the calibration of the position or velocity is performed on-line and off-line. In the on-line calibration stage, the complementary filter technique is used, where a Kalman filter plays an important role. In the off-line calibration stage, the constant component of the resultant navigational error of the system is removed using the velocity information and motion detection algorithm. The effectiveness and feasibility of the presented system is shown through the experimental results.

• Journal of Advanced Navigation Technology
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• v.19 no.5
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• pp.389-394
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• 2015

This paper considers the transfer alignment in the inertial navigation system which has lever-arm and the time delay in the velocity measurement. We suggest a method to improve the performance of the velocity matching. First, we analyze the estimation performance of the velocity matching through the tuning of the two covariance matrices of process noise and measurement noise. Next we provide some maneuvering conditions of the vehicles to improve the estimation performance using the observability analysis. The analysis results are verified using the computer simulations, which show that cruise movements do not provide the azimuth estimation of the vehicles, while east or north accelerating movement can provide.

• Journal of Korean Society for Geospatial Information Science
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• v.2 no.2 s.4
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• pp.81-88
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• 1994

The CNS(Car Navigation System) is used more generally in driver aid system than ALV(Auto nomous Land Vehicle) research area. In this paper we developed a new position tracking algorithm for the Global Path Planning in the CNS. In japan, CNS is already well developed and, thesedays they sell CNS products about $400{\sim}500$ thousands per year, and USA and European Communications(EC), too. In Korea, studies of the first generation CNS, which finds current location of a navigating vehicle and displays its location in a Digital-Map with real-time are progressing but still in the beginning step. Therefore a new position tracking algorithm is presented, which reduces vehicle position error dramatically by fusing GPS and dead-reckoning sensors. And the validity of our algorithm is demonstrated by the experimental results with the real car.

• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.78-85
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• 2005

Initial alignment and localization are important topics in inertial navigation systems, since misalignment and initial position error wholly propagate into the navigation systems and deteriorate the performance of the systems. This paper presents the error convergence characteristics of the hybrid navigation system for underwater vehicles initial position, which is based on an inertial measurement unit (IMU) accompanying a range sensor. This paper demonstrates the improvement on the navigational performance oj the hybrid system with the range information, especially focused on the convergence of the estimation of underwater vehicles initial position error. Simulations are performed with experimental data obtained from a rotating ann test with a fish model. The convergence speed and condition of the initial error removal for random initial position errors are examined with Monte Carlo simulation. In addition, numerical simulation is conducted with an AUV model in lawn-mowing survey mode to illustrate the error convergence of the hybrid navigation System for initial position error.

• Journal of Advanced Navigation Technology
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• v.26 no.5
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• pp.319-324
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• 2022

If radio interference occurs or there is no navigation device, radio navigation of high-speed moving object becomes impossible. Nevertheless, if there are multiple ground stations and precise range measurement between the high-speed moving object and the ground station can be secured, it is possible to estimate the position of moving object. This paper proposes a position estimation method using high-precision TDOA measurement generated using TLM signal. In the proposed method, a common error of moving object is removed using the TDOA measurements. The measurements is generated based on TLM signal including SOQPSK PN symbol capable of precise timing synchronization. Therefore, since precise timing synchronization of the system has been performed, the timing error between ground stations has a very small value. This improved the position estimation performance by increasing the accuracy of the measured values. The proposed method is verified through software-based simulation, and the performance of estimated position satisfies the target performance.

• Journal of Advanced Navigation Technology
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• v.20 no.1
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• pp.29-36
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• 2016

Accuracy of GPS (global positioning system) deteriorates dramatically or positioning is impossible in urban area occasionally since high-rise buildings and elevated roads make the reception of navigation signal very difficult so that number of visible satellites decreases. In these cases, vertical error usually becomes much larger than the horizontal error due to the intrinsic geometry of GPS satellites. To obtain more accurate and reliable height information, this paper proposes a hybrid method that combines GPS and a low-cost barometric altimeter. In the proposed method, the sea-level pressure and the sea-surface temperature are applied to the output of the altimeter. Next, the difference between the ellipsoid and the geoid is compensated. Finally, a simple Kalman filter combines the compensated barometric altitude and the GPS height. By static and car experiments, performance of the proposed method is evaluated. By the experiment results, it can be seen that the proposed method improves the altitude accuracy considerably.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.310-317
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• 2017

Recently, many nations are operating and developing Global Navigation Satellite System (GNSS). Also, Satellite Based Augmentation System (SBAS), which uses the geostationary orbit, is operated presently in order to improve the performance of GNSS. The most widely-used SBAS is Wide Area Augmentation System (WAAS) of GPS developed by the United States. SBAS uses various algorithms to offer guaranteed accuracy, availability, continuity and integrity to its users. There is algorithm for guarantees the integrity of the satellite. This algorithm calculates the satellite errors, generates the correction and provides it to the users. The satellite orbit errors are calculated in three-dimensional space in this step. The reference placement is crucial for this three-dimensional calculation of satellite orbit errors. The wider the reference placement becomes, the wider LOS vectors spread, so the more the accuracy improves. For the next step, the regional features of the US and Korea need to be analyzed. Korea has a very narrow geographic features compared to the US. Hence, there may be a problem if the three-dimensional space method of satellite orbit error calculation is used without any modification. This paper suggests a method which uses scalar values to calculate satellite orbit errors instead of using three-dimensional space. Also, this paper proposes the feasibility for this method for a narrow area. The suggested method uses the scalar value, which is a projection of orbit errors on the LOS vector between a reference and a satellite. This method confirms the change in errors according to the baseline distance between Korea and America. The difference in the error change is compared to present the feasibility of the proposed method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.82-89
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• 1999

미국의 전파항법정책(FRP Federal Radionavigation Plan)은 여전히 SA정책(미국방성에서 GPS 위성 궤도에 오차를 실어 전파발사를 하는 정책)을 유지하고 있고, P(Y)코드 접속에 의한 고정밀 위치정보 사용 역시 미군 및 NATO군 등 미 국방성에서 인가한 사용자에게만 허용되고 있는 관계로 그 외의 사용자는 3차원 고정밀 위치정보가 요구되는 항공기 이착륙 유도시스템, 해ㆍ육상 정밀 구조/탐색 및 육ㆍ해ㆍ공 특수목적 등에 군사용 P(Y)코드대신 DGPS를 사용하고 있다. 본 연구는 한반도 남해안 및 동해안 일부까지를 유효거리로 하고 있는 일본 Marine Radiobeaeon/DGPS 시스템에 대한 한반도 연근해에서의 위치정보 사용 가능성을 확인하기 위해 한반도 남해안에서 측정 가능한 일본 DGPS국을 선택 모델로 하여 DGPS Data 측정실험 및 위치정보 정밀도 분석을 하였다. 연구결과 군사용 P(Y) 코드수준의 정밀도를 유지하고 있어 곧 구축 예정인 한국형 DGPS 국가망과 함께 선택적으로 사용할 수 있음을 확인하였다.