• Journal of information and communication convergence engineering
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• 제2권3호
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• pp.202-204
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• 2004

An improvement of tracking capacity to find a position of the Iris images is presented in this paper. The propose algorithm is used the Four Points Diagonal Positioning algorithm that the image is positioned with arbitrary 4 points on the edge of iris and the selective 4 points are drawn by a diagonal line on the cross. The experiment result shows that the algorithm is efficient to track on the eyelid.

• Journal of Positioning, Navigation, and Timing
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• 제8권1호
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• pp.19-29
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• 2019

This paper analyzes the design factors for GNSS anti-jamming receiver system in which the adaptive beamforming algorithm is applied in GNSS receiver system. The design analysis factors used in this paper are divided into three: antenna, beamforming algorithm, and operation environment. This paper analyzes the above three factors and presents numerical simulation results on antenna and beamforming algorithm.

• 한국멀티미디어학회논문지
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• 제21권5호
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• pp.583-591
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• 2018

With the development of ICT(Information and Communication Technology), the number of smart devices is rapidly increasing. LBS(Location Based Service) applications that provide user's location based service are used in various fields. There is also a growing demand for indoor precision positioning technology to provide seamless services. In this paper, we propose an indoor positioning system that estimates the location of a smartphone user. The proposed algorithm determines whether the received signal is LOS(Line-of-Sight) or NLOS(Non-Line of-Sight) in order to decrease multipath effect by the indoor environment. The proposed positioning algorithm is very simple and requires only the AP(Access Point) coordinates. In addition, it requires only two APs for estimating the location of a smartphone user. The proposed algorithm is a practically applicable technology without any additional hardware and kernel modification in the smartphone. In the experiment results, the reliability of the positioning system was found to be within 0.83 m.

• Journal of Positioning, Navigation, and Timing
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• 제10권4호
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• pp.243-251
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• 2021

Real-Time Kinematic (RTK) is a phase-based differential GNSS technique and uses additional observations from permanent reference stations to mitigate or eliminate effects like atmospheric delays or satellite clocks and orbit errors. In particular, as the position accuracy required in the fields of autonomous vehicles and drones is gradually increasing, the demand for RTK-based precise navigation that can provide cm-level position is increasing. Recently, with the rapid growth of the open-source software market, the use of open-source software for building navigation system of unmanned vehicles, which is difficult to mount an expensive GNSS receivers, is gradually increasing. RTKLIB is an open-source software package that can perform RTK positioning and is widely used for research and education purposes. However, since the performance and stability of RTK algorithm of RTKLIB is inevitably inferior to that of commercial GNSS receivers, users need to verify whether RTKLIB can satisfy the navigation performance requirements of unmanned vehicles. Therefore, in this paper, the performance evaluation of the RTK positioning algorithm of RTKLIB was performed using GNSS observation data acquired in a dynamic environment. Therefore, in this paper, the RTK positioning performance of RTKLIB was evaluated using GNSS observation data acquired in a dynamic environment. Our results show that the current RTK algorithm of RTKLIB is not suitable for precise navigation of unmanned vehicles.

• 대한전자공학회논문지TC
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• 제46권4호
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• pp.86-94
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• 2009

현재 위치기반서비스(LBS : Location Based Service) 를 위해 사용되고 있는 위치측위 방식은 GPS 기반의 측위 방식과 이동통신망을 이용한 네트워크 기반의 측위기술들이 있다. 그러나 GPS 와 네트워크기반의 측위 방식은 비가시선 효과(NLOS) 와 중계기에 의한 전파 지연 발생 때문에 위치측위 정확도가 저하되는 문제점이 있다. 이러한 단점을 보완하기 위해 현재 CDMA 시스템에서는 패턴매칭(Pattern Matching) 알고리즘을 사용한다. 패턴매칭 알고리즘은 GPS 에 의한 위치측위 시 측정된 RF 신호의 전파 특성을 측위 된 위치와 함께 데이터베이스로 구축하여, 사용자의 측위 요청이 있을 때 수신신호의 전파특성과 데이터베이스를 비교하여 위치를 제공하는 방식이다. 그러나 패턴매칭 알고리즘은 GPS 신호를 수신할 수 없는 음영 지역과 실내 에서는 데이터베이스가 구축되어지지 않는다. 패턴매칭 알고리즘은 데이터베이스의 위치 정보가 위치측위를 요청하는 사용자의 위치를 결정하기 때문에 데이터베이스가 구축이 되지 않는 지역에서는 측위정확도의 오차가 발생하게 된다. 따라서 본 논문에서는 현재 CDMA 시스템에서 사용하는 패턴매칭 알고리즘의 위치측위 성능을 분석하고 패턴매칭 알고리즘을 이용한 위치측위 시스템의 성능을 향상시키기 위해서 신호세기 예측 알고리즘을 이용하여 현재 구축이 되지 않은 지역의 데이터베이스를 구축하기 위한 알고리즘을 제안하였다. 제안하는 알고리즘으로 데이터베이스가 없는 지역의 신호세기를 예측하여 데이터베이스를 구축한 후 패턴매칭 알고리즘의 위치측위 성능을 분석하였다.

• 한국측량학회지
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• 제37권5호
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• pp.397-402
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• 2019

Recently, with the emergence of autonomous vehicles and the increasing interest in safety, a variety of research has been being actively conducted to precisely estimate the position of a vehicle by fusing sensors. Previously, researches were conducted to determine the location of moving objects using GNSS (Global Navigation Satellite Systems) and/or IMU (Inertial Measurement Unit). However, precise positioning of a moving vehicle has lately been performed by fusing data obtained from various sensors, such as LiDAR (Light Detection and Ranging), on-board vehicle sensors, and cameras. This study is designed to enhance kinematic vehicle positioning performance by using feature-based recognition. Therefore, an analysis of the required precision of the observations obtained from the images has carried out in this study. Velocity and attitude observations, which are assumed to be obtained from images, were generated by simulation. Various magnitudes of errors were added to the generated velocities and attitudes. By applying these observations to the positioning algorithm, the effects of the additional velocity and attitude information on positioning accuracy in GNSS signal blockages were analyzed based on Kalman filter. The results have shown that yaw information with a precision smaller than 0.5 degrees should be used to improve existing positioning algorithms by more than 10%.

• 한국정보통신학회논문지
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• 제22권2호
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• pp.302-313
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• 2018

스마트 기기의 생활화와 증강현실 활용 증가로 실내 위치 인식 시스템의 수요가 급증함에 따라, BLE(Bluetooth Lower Energy) 비콘 그리고 UWB(Ultra Wide Band) 등을 이용한 실내 측위 시스템이 개발되고 있다. 본 논문에서는 BLE Beacon을 기반으로 RSSI(Received Signal Strength Indicator)를 이용한 삼변측량(Trilateration) 기법을 사용하여 측위 플레이트(Plate)를 생성한다. 이에 IMU(Inertial Measurement Unit) 센서의 방향, 속도, 이동거리 등의 데이터를 이용하여 PDR(Pedestrian Dead Reckoning) 측위 좌표를 산출하여 정확도를 보정한다. 또, BLE 비콘(Beacon)의 RSSI를 적용한 플레이트(Plate) 기법과 PDR 기법이 융합된 정밀 실내 측위 알고리즘을 제안한다. 본 논문에서 제시한 알고리즘을 실제 대형 실내 경기장과 공항에 BLE 비콘을 설치, 실험하여 평균 2.2m 의 오차로 65%의 정확도가 개선됨을 검증하였다.

• 대한임베디드공학회논문지
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• 제7권2호
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• pp.85-93
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• 2012

In this paper, we proposed Wireless LAN (WLAN) localization method that enhances database construction based on weighting factor and analyse the characteristic of the WLAN received signals. The weighting factor plays a key role as it determines the importance of Received Signal Strength Indication (RSSI) value from number of received signals (frequency). The fingerprint method is the most widely used method in WLAN-based positioning methods because it has high location accuracy compare to other indoor positioning methods. The fingerprint method has different location accuracies which depend on training phase and positioning phase. In training phase, intensity of RSSI is measured under the various. Conventional systems adapt average of RSSI samples in a database construction, which is not quite accurate due to variety of RSSI samples. In this paper, we analyse WLAN RSSI characteristic from anechoic chamber test, and analyze the causes of various distributions of RSSI and its influence on location accuracy in indoor environments. In addition, we proposed enhanced weighting factor algorithm for accurate database construction and compare location accuracy of proposed algorithm with conventional algorithm by computer simulations and tests.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.157-166
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• 2023

Several experiments were carried out to analyze the impact of the modernized Global Positioning System (GPS) L2C signal on pseudorange-based point positioning. Three dual-frequency positioning algorithms, ionosphere-free linear combination, ionospheric error estimation, and simple integration, were used, and the results were compared with those of Standard Point Positioning (SPP). An analysis was conducted to determine the characteristics of each dual-frequency positioning method, the impact of the magnitude of ionospheric error, and receiver grade. Ionosphere-free and ionospheric error estimation methods can provide improved positioning accuracy relative to SPP because they are able to significantly reduce the ionospheric error. However, this result was possible only when the ionospheric error reduction effect was greater than the disadvantage of these dual-frequency positioning algorithms such as the increment of multipath and noise, impact of uncertainty of unknown parameter estimation. The RMSE of the simple integration algorithm was larger than that of SPP, because of the remaining ionospheric error. Even though the receiver grade was different, similar results were observed.

• Journal of Positioning, Navigation, and Timing
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• 제6권2호
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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%.