• 한국항행학회논문지
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• 제21권3호
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• pp.258-263
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• 2017

본 논문에서는 간섭상쇄 기능을 갖춘 지역전파항법 수신기의 GNSS (global navigation satellite system) 위성항법신호 획득성능을 분석하였다. GNSS 항법신호와 동일 주파수영역에 지역전파항법 신호를 사용하여 통합 항법을 수행할 경우 혼신에 의한 영향이 발생하나, 이는 순차적 간섭신호상쇄 알고리즘 등과 같은 간섭상쇄 기술을 통해 어느 정도 극복 가능하다. 하지만 J/S(jamming-to-signal ratio)가 클 경우 잔여 신호와 GNSS신호와의 교차상관 특성에 의해 신호획득 시 잘못 된 검출결과를 보일 수 있다. 본 논문은 Kasami코드를 사용할 경우 GNSS신호와의 혼신에 의한 신호획득 성능저하를 Monte Carlo 시뮬레이션을 통해 분석해 보았으며, 비교를 위해 GNSS Gold 코드의 신호획득 성능과 비교하였다.

• 한국측량학회지
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• 제34권4호
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• pp.425-430
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• 2016

Currently, start of the operation US GPS, the Russian Glonass, European Galileo, the Chinese Compass satellites for positioning are celebrating a true GNSS (Global Navigation Satellite System) generation. Korea is building advanced infrastructure such as a national network consisting of CORS (Continuously Operating Reference Station), VRS service for real-time precise positioning and perform continuous upgrading. However, the acquisition of geospatial information using the national infrastructure requires many steps and high dependence on foreign software part in this process. This study contributes to advanced construction technology of geospatial information by design of realtime GNSS surveying system. As a results, it has designed the surveying software that can effectively positioning realtime. Designed realtime surveying software can utilized in various fields.

• ETRI Journal
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• 제38권6호
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• pp.1172-1178
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• 2016

The atmospheric meteorology parameters of the earth, such as temperature, pressure, and humidity, strongly influence the propagation of signals in Global Navigation Satellite Systems (GNSSs). The propagation delays associated with GNSS signals can be modeled and explained based on the atmospheric temperature, pressure, and humidity, as well as the locations of the satellites and receivers. In this paper, we propose an optimized and simplified low cost GNSS base weather station that can be used to provide a global estimate of the integrated water vapor value. Our algorithm can be used to measure the zenith tropospheric delay based on the measured propagation delays in the received signals. We also present the results of the data measurements performed at our station located in the Tlemcen region of Algeria.

• Journal of Positioning, Navigation, and Timing
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• 제12권3호
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• pp.289-294
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• 2023

As technologies such as cameras, Laser Imaging, Detection, and Ranging (LiDAR), and Global Navigation Satellite Systems (GNSS) become more sophisticated and common, their use in autonomous driving technologies is being explored in various fields. In the maritime area, technologies related to collision avoidance between ships are being developed to evaluate and avoid the risk of collision between ships by setting various scenarios. However, the position of each vessel used in the process of developing collision avoidance technology between vessels uses data obtained through GNSS, and may include a position error of 10 m or more depending on the situation. In this paper, a study on the dynamic safety navigation range including the positional inaccuracy of the ship is conducted. By combining the concept of the protection level obtained using GNSS raw data with a conventional safe navigation range, a safer navigation range can be calculated for dynamic navigation. The calculated range is verified using data obtained while sailing in an actual sea environment.

• 한국측량학회지
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• 제39권5호
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• pp.289-295
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• 2021

Recently, owing to the development of autonomous vehicles, research on precisely determining the position of a moving object has been actively conducted. Previous research mainly used the fusion of GNSS/IMU (Global Positioning System / Inertial Navigation System) and sensors attached to the vehicle through a Kalman filter. However, in recent years, new technologies have been used to determine the location of a moving object owing to the improvement in computing power and the advent of deep learning. Various techniques using RNN (Recurrent Neural Network), LSTM (Long Short-Term Memory), and NARX (Nonlinear Auto-Regressive eXogenous model) exist for such learning-based positioning methods. The purpose of this study is to compare the precision of existing filter-based sensor fusion technology and the NARX-based method in case of GNSS signal blockages using simulation data. When the filter-based sensor integration technology was used, an average horizontal position error of 112.8 m occurred during 60 seconds of GNSS signal outages. The same experiment was performed 100 times using the NARX. Among them, an improvement in precision was confirmed in approximately 20% of the experimental results. The horizontal position accuracy was 22.65 m, which was confirmed to be better than that of the filter-based fusion technique.

• Journal of Positioning, Navigation, and Timing
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• 제12권1호
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• pp.1-9
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• 2023

The problem of classifying a non-line-of-sight (NLOS) signal in a multipath channel is important to improve global navigation satellite system (GNSS) positioning accuracy in urban areas. Conventional deep learning-based NLOS signal classifiers use GNSS satellite measurements such as the carrier-to-noise-density ratio (CN_0), pseudorange, and elevation angle as inputs. However, there is a computational inefficiency with use of these measurements and the NLOS signal features expressed by the measurements are limited. In this paper, we propose a Convolutional Neural Network (CNN)-based NLOS signal classifier that receives successive Auto-correlation function (ACF) outputs according to a time-series, which is the most primitive output of GNSS signal processing. We compared the proposed classifier to other DL-based NLOS signal classifiers such as a multi-layer perceptron (MLP) and Gated Recurrent Unit (GRU) to show the superiority of the proposed classifier. The results show the proposed classifier does not require the navigation data extraction stage to classify the NLOS signals, and it has been verified that it has the best detection performance among all compared classifiers, with an accuracy of up to 97%.

• 한국항행학회논문지
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• 제16권6호
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• pp.935-943
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• 2012

본 논문에서는 위성항법기반 교통인프라 기술개발의 네트워크 수신국 사이트 선정을 위하여 사전 조사, 현장 조사, 현장 환경 분석의 3단계 선정 절차를 제시하였으며 실제 테스트베드인 오창 지역을 기준으로 4개의 후보지를 도출하였다. IGS, NGS 등과 같은 국제상시관측기관이 제안하는 사이트 선정 권고안을 정리하여 위성항법기반 교통인프라 기술개발에 적합한 요구사항을 도출하고 이를 만족하는 1차 후보군을 선정하는 작업이 사전조사이며, 1차 후보군에 대한 육안 가시검사 및 환경, 기타 조사를 통하여 2차 후보군을 선정하는 작업이 현장조사이다. 또한 선정된 2차 후보군에 대해 상공장애도 분석과 전파환경 분석을 통해 최종적으로 수신국 사이트 후보지를 선정하는 것이 현장 환경 분석이다. 위와 같은 일련의 선정 절차를 통해 1차 16개 후보군, 2차 7개 후보군, 3차 최종 4개의 수신국 사이트를 효과적으로 선정할 수 있었다.

• 전자공학회논문지
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• 제52권3호
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• pp.13-18
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• 2015

본 논문은 GNSS의 문제점인 위치오차와 실외음영지역을 해소하기 위하여 GNSS와 vision system을 융합한 신뢰성있는 고정밀 측위와 최적의 vision system을 분석하였다. 위치결정을 위해서는 최소 4개 이상의 GNSS로부터 신호를 수신 받아야 한다. 그러나 도심지역에서는 고층건물이나 장애물 또는 반사파에 의해 정확한 위치가 어렵다. 이러한 문제점을 해결하기 위하여 vision system을 이용한다. GNSS를 사용하기 열악한 도심지역의 target object에 정확한 위치 값을 결정해 놓는다. 그리고 vision system을 이용해 target object를 인식하고, 인식된 target object를 이용하여 위치오차를 보정해 준다. 이동체는 이동 중 vision system을 이용하여 target object를 인식하여 위치 데이터 값을 만들어내고, 위치 계산을 수정하여 안정되고 신뢰성 있는 고정밀 측위를 할 수 있다.

• Journal of Positioning, Navigation, and Timing
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• 제12권1호
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• pp.51-58
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• 2023

Geofencing supports unmanned aerial vehicle (UAV) operation by defining stay-in and stay-out regions. National Aeronautics and Space Administration (NASA) has developed a prototype of the geofencing function, SAFEGUARD, which prevents stayout region violation by utilizing position estimates. Thus, SAFEGUARD depends on navigation system performance, and the safety risk associated with the navigation system uncertainty should be considered. This study presents a methodology to compute the safety risk assessment-based along-track position error bound under nominal and Global Navigation Satellite Systems (GNSS) failure conditions. A Kalman filter system using pseudorange measurements as well as pseudorange rate measurements is considered for determining the position uncertainty induced by velocity uncertainty. The worst case pseudorange and pseudorange rate fault-based position error bound under the GNSS failure condition are derived by applying a Receiver Autonomous Integrity Monitor (RAIM). Position error bound simulations are also conducted for different GNSS fault hypotheses and constellation conditions with a GNSS/INS integrated navigation system. The results show that the proposed along-track position error bounds depend on satellite geometries caused by UAV attitude change and are reduced to about 40% of those of the single constellation case when using the dual constellation.