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GPS Satellite State Vector Determination in ECI Coordinate System using the Civil Navigation Message
Kim, Ghangho,Jeon, Sanghoon,Kee, Changdon,No, Tae Soo,Kwon, Kiho,Choi, Seungwoon Cambridge University Press 2014 The Journal of navigation Vol.67 No.1
<P>A closed form of an algorithm to determine a Global Positioning System (GPS) satellite's position, velocity and acceleration is proposed, and an Earth Centred Earth Fixed (ECEF) to Earth Centred Inertial (ECI) transformation result using the Civil Navigation (CNAV) message is presented in this paper. To obtain the closed form of the GPS satellite velocity and acceleration determination algorithm using the CNAV, we analytically differentiated the IS-GPS-200F position determination function. The calculated data are transformed from the International Terrestrial Reference Frame (ITRF) to the Geocentric Celestial Reference Frame (GCRF) using an equinox-based transform algorithm that is defined in the IAU-2000 resolution system using the Earth Orientation Parameter (EOP) data. To verify the correctness of the proposed velocity and acceleration determination algorithm, the analytical results are compared to the numerical result. The equinox-based transformation result is compared to simple rotation about the z-axis, which does not use the EOP. The results show that by using the proposed algorithm and the equinox-based transformation together, the user can obtain more accurate navigation data in the ECI frame.</P>
The Development of Modularized Post Processing GPS Software Receiving Platform
Ghangho Kim,Hyoungmin So,Sanghoon Jeon,Changdon Kee,Youngsu Cho,Wansik Choi 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
Modularized GPS software defined radio (SDR) software platform has many advantages of applying and modifying algorithm. Hardware based GPS receiver uses many hardware parts (such as RF front, correlators, CPU and others) that process tracked signal and navigation data to calculate user position, while SDR uses software modules, which run on general purpose CPU platform, to implement same function. SDR needs not change hardware part and it is not limited by hardware capability when new processing algorithm is required. The weakness of SDR is that software correlation takes lots of processing time. However, in these days the evolution of MPU and DSP, and the size minimization of general purpose CPU increase the competitiveness of SDR against the hardware GPS receiver. This paper presents a study of modulization of GPS SDR software platform and development of the GNSS SDR software platform using MATLAB Simulink™. We focus on especially post processing SDR platform which is usually adapted in research area. The main functions of SDR are GPS signal acquisition, signal tracking, decoding navigation data and calculating stand alone user position from stored data that was intermediate frequency (IF) down converted and sampled. Each module of SDR platform is categorized by function for applicability. The developed SDR software platform was tested using stored data that IF down converted and sampled. The test results present that the SDR software platform calculates user position properly.
Pseudolite Antenna Calibration Algorithm using a Multi-Antenna Receiver
Chongwon Kim,Sanghoon Jeon,Ghangho Kim,Changdon Kee,Taikjin Lee,Hyoungmin So 한국항공우주학회 2012 International Journal of Aeronautical and Space Sc Vol.13 No.2
The need for position information in indoor environments has been growing lately. Several indoor navigation systems have been studied. Among them, pseudolite-based indoor positioning systems are one of the best systems to obtain precise position measurements. However, the installation of such systems is very difficult because the calibration of pseudolite antenna position is complicated. For precise calibration, the use of carrier phase measurements is necessary, and whenever carrier phase measurements are considered, problems with cycle ambiguity appear. In this paper, a new approach to calibrate the positions of pseudolite antennas is proposed. By using a multi-antenna, the ambiguity can be eliminated, epoch by epoch, for every single carrier phase measurement. Moreover, the number of calibration points can be reduced down to 3 by use of measurements collected at unknown positions. Using the proposed methods, the process of the collection of carrier phase measurements becomes considerably simple and convenient. Simulation results are presented to verify the proposed algorithms.
Modified High-Resolution Correlator Technique for Short-Delayed Multipath Mitigation
So, Hyoungmin,Kim, Ghangho,Lee, Taikjin,Jeon, Sanghoon,Kee, Changdon Cambridge University Press 2009 The Journal of navigation Vol.62 No.3
<P>Multipath is one of the main error sources in global navigation satellite system (GNSS) positioning. The high-resolution correlator (HRC) is a multipath mitigation technique well known for its outstanding performance for mid-delayed multipath, but still has a remaining error for the short-delayed multipath. This paper proposes a modified HRC scheme that can remove or reduce the error for short-delayed multipath signals. It estimates the HRC tracking error and augments the conventional HRC with the estimates. The method was implemented with a software receiver and the test results show short-delayed multipath-induced errors were reduced to about one third of those from the conventional HRC.</P>
A Study on Earth-Moon Transfer Orbit Design
Tae Soo No,Ji Marn Lee,Gyeong Eon Jeon,Daero Lee,Ghangho Kim 한국항공우주학회 2012 International Journal of Aeronautical and Space Sc Vol.13 No.1
Optimal transfer trajectories based on the planar circular restricted three body problem are designed by using mixed impulsive and continuous thrust. Continuous and dynamic trajectory optimization is reformulated in the form of discrete optimization problem. This is done by the method of direct transcription and collocation. It is then solved by using nonlinear programming software. Two very different transfer trajectories can be obtained by the different combinations of the design parameters. Furthermore, it was found out that all designed trajectories permit a ballistic capture by the Moon’s gravity. Finally, the required thrust profiles are presented and they are analyzed in detail.