Enhanced GPS Measurements Simulation for Space-oriented Navigation System Design

AbstractAt the stage of preliminary scheme and algorithm design for spaceborne navigation systems, a precise and high-fidelity software global positioning system (GPS) simulator is a necessary and feasible testing facility in laboratory environments, with consideration of the tradeoffs where possible. This article presents a software GPS measurements simulator on the L1 C/A code and carrier signal for space-oriented navigation system design. The simulator, coded in MATLAB language, generates both C/A code pseudorange and carrier phase measurements. Mathematical models in the Earth centered inertial (ECI) frame are formulated to simulate the GPS constellation and to generate GPS measurements. A series of efficient measures are investigated and utilized to rationalize the enhanced simulator, in terms of ephemeris data selection, space ionospheric model and range rate calculation, etc. Such an enhanced simulator has been facilitating our current work for designing a space integrated GPS/inertial navigation system (INS) navigation system. Consequently, it will promote our future research on space-oriented navigation system

Ambiguity Function Method Scheme for Aircraft Attitude Sensor Utilising GPS/GLONASS Carrier Phase Measurement

When the receivers of GPS, GLONASS, COMPASS and other such systems are equipped with multiple antennas, they can give attitude information. Based on the difference carrier phase equations established in local level frame (LLF), a new algorithm is presented to resolve aircraft attitude determination problems in real-time. Presuming that the cycle integer ambiguity is known, the measurement equations have attitude analytical resolutions using single difference (SD) equations of two navigation satellites in-view. Similar with SD process, the doubledifference (DD) measurements are established and analysed. In addition, the SD and DD algorithms are capable of reducing the integer search space into some discrete point space and then the ambiguity function method (AFM) resolves the ambiguity function within the point solutions space. Therefore the procedures have very low computation, thus saving time. The hardware architecture has been realised using multiple  GPS/GLONASS OEMs. The experimental results have demonstrated that the proposed approach is effective and can satisfy the requirement of real-time application in cases of GPS, and combined GPS, and GLONASS.Defence Science Journal, 2009, 59(5), pp.466-470, DOI:http://dx.doi.org/10.14429/dsj.59.154

Robust Extrinsic Self-Calibration of Camera and Solid State LiDAR

This letter proposes an extrinsic calibration approach for a pair of monocular camera and prism-spinning solid-state LiDAR. The unique characteristics of the point cloud measured resulting from the flower-like scanning pattern is first disclosed as the vacant points, a type of outlier between foreground target and background objects. Unlike existing method using only depth continuous measurements, we use depth discontinuous measurements to retain more valid features and efficiently remove vacant points. The larger number of detected 3D corners thus contain more robust a priori information than usual which, together with the 2D corners detected by overlapping cameras and constrained by the proposed circularity and rectangularity rules, produce accurate extrinsic estimates. The algorithm is evaluated with real field experiments adopting both qualitative and quantitative performance criteria, and found to be superior to existing algorithms. The code is available on GitHub

Assessing Radio Frequency Compatibility Between Galileo and Compass (Review Paper))

The radio frequency compatibility between Galileo and Compass has become a matter of great concern for the system providers and user community. This paper mainly deals with the intersystem interference between Galileo and Compass systems and displays some important analysis results. First, a comprehensive methodology for the radio frequency compatibility assessment is described, considering the geometry-dependent and time-varying terms such as space constellation, signal modulation, emission power level, space loss, satellite antenna gain, and user receiver characteristic. Second, real simulations were carried out to assess the interference effects where Galileo and Compass signals were sharing the same band. Simulation results show that Compass introduces intersystem interference to Galileo, but the interference effects are lower than those of Compass interfered to Galileo signals. In addition, the radio frequency compatibility in Asia-Pacific region was analysed. It was found that the maximum interference suffered by Galileo from Compass was below 0.25dB under existing rules of coordination at International Telecommunication Union (ITU). In other words, Compass can provide a sound basis for compatibility with Galileo.Defence Science Journal, 2011, 61(6), pp.545-553, DOI:http://dx.doi.org/10.14429/dsj.61.28