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RTK GPS/INS/스테레오 카메라를 활용한 3 차원 지도 기반 복합 항법의 공간 정보 생성 시스템
이유담(Yu Dam Lee),최광호(Kwang Ho Choi),임준후(Joon Hoo Lim),유원재(Won Jae Yoo),김라우(La Woo Kim),이형근(Hyung Keun Lee) 제어로봇시스템학회 2018 제어·로봇·시스템학회 논문지 Vol.24 No.8
This paper proposes a method to obtain absolute coordinates of considerably many point clouds on designated objects by integrating Global Positioning System (GPS), an Inertial Navigation System (INS), and a stereo camera. Compared with existing methods, the proposed method enables acquiring absolute coordinates instead of relative coordinates of point clouds with respect to a global reference frame. The GPS receiver and INS sensor are used for acquiring absolute coordinates and attitude parameters of the camera. The stereo camera is used to capture image pairs to compute relative coordinates of point clouds by feature-based image matching method. In addition, a Real-Time Kinematic (RTK) software is utilized to estimate accurate coordinates of the camera, and a time synchronization method between different systems to which sensors are connected is proposed. Based on the estimated absolute coordinates and attitude parameters of the camera, the relative coordinates of point clouds with respect to the camera are converted to the absolute coordinates.
Design of SDR-based Multi-Constellation Multi-Frequency GNSS Signal Acquisition/Tracking Module
유원재,김라우,이유담,이택근,이형근 항법시스템학회 2021 Journal of Positioning, Navigation, and Timing Vol.10 No.1
Due to the Global Navigation Satellite System (GNSS) modernization, the recently launched GNSS satellites transmit signals at various frequency bands of L1, L2 and L5. Considering the Korea Positioning System (KPS) signal and other GNSS augmentation signals in the future, there is a high probability of applying more complex communication techniques to the new GNSS signals. For the reason, GNSS receivers based on flexible Software Defined Radio (SDR) concept needs to be developed to evaluate various experimental communication techniques by accessing each signal processing module in detail. In this paper, we introduce a multi-constellation (GPS/Galileo/BeiDou) multi-band (L1/L2/L5) SDR by utilizing Ettus USRP N210. The signal reception module of the developed SDR includes down-conversion, analog-to-digital conversion, signal acquisition, and tracking. The down-conversion module is designed based on the super-heterodyne method fitted for MHz sampling. The signal acquisition module performs PRN code generation and FFT operation and the signal tracking module implements delay/phase/frequency locked loops only by software. In general, it is difficult to sample entire main lobe components of L5 band signals due to their higher chipping rate compared with L1 and L2 band signals. Experiment result shows that it is possible to acquire and track the under-sampled signals by the developed SDR.
SDR 기반 다중 GNSS/다중 주파수 신호 획득 및 검증
유원재,김라우,이유담,이형근 한국항해항만학회 2020 한국항해항만학회 학술대회논문집 Vol.2020 No.춘계
현재 해상에서 항해하는 선박들은 미국의 Global Positioning System (GPS)와 같은 Global Navigation Satellite System (GNSS)에 크게 의존하고 있다. 근래에 들어, 미국의 GPS 뿐만 아니라 러시아의 GLObal NAvigation Satellite System (GLONASS), 유럽 연합의 Galileo 및 중국의 BeiDou와 같은 GNSS들이 다수 운용됨에 따라 단일 GNSS가 아닌 다중 GNSS를 사용함으로써 측정치 개수를 증가시켜 위치 오차를 감소시키어 선박 자율 항해를 위한 기초 방안들이 활발히 연구 되고 있다. 본 논문에서는 GNSS 현대화에 의해 향후 추가될 주파수 대역 신호 및 변조 기법 등을 유연하게 대처할 수 있는 Software Defined Radio(SDR)를 통해 다중 GNSS/다중 주파수 신호를 획득하는 기법을 설계하였다. 개활지에서 GNSS 신호 획득 실험을 수행하여, 신호 획득 결과 및 사용자 위치 오차 분석을 통해 측정치에 대한 검증을 수행하였다.