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The time-hopping (TH) pulsed pseudolite (PL) can be used to enhance the performance of global navigation satellite systems (GNSS), and the slot index table (SIT) is an important part to form this PL signal. In this paper, a new method to generate SITs for multiple PLs is proposed. The general process of the proposed method is that first different time-hopping slot index (THSI) base matrices are generated based on the constructed congruence codes, and then by combining several different THSI base matrices to constitute a new matrix, the SIT for a PL is formed. Further by changing the combined matrices, different SITs for different PLs can be generated. During this process, two critical factors that affect the performance of the given method, i.e., the collision or hit property of the generated THSI base matrix and the correlation property of the formed SIT, are analyzed in detail. The simulations given at the end of this paper show that compared with many other similar schemes, the SITs given by the proposed method can obtain better correlation performance and detection performance in the receiver, and these results also imply that the proposed method offers a more effective way to design this kind of PL signal. [ABSTRACT FROM AUTHOR]

Article presented the security issues of the means of transport which apply global navigation satellite systems, with a particular emphasis on transport safety and the risks resulting from the use of those systems. Presented method of detecting spoofing attacks of the global satellite navigation system involves collecting navigational position readings and comparing them with the current vehicle speed read from the vehicle's speedometer (SoV) and sequential testing of GNSS and SoV readings. Proposed a way automatic speedometer calibration to specified threshold value (D). A physical experiment was carried out to confirm the assumptions of the above-mentioned method, the results of which are that when the car appears in range of spoofer, its speed, as stated by the NMEA RMC readings, was equal to the spoofer speed (0 km/h). [ABSTRACT FROM AUTHOR]

The possibility of computing a traverse having no base angles at the takeoff and closing control stations has been previously published in Chukwuocha et al. (2017). In this computational method, the azimuth of the first traverse leg is indirectly determined between a pair of orphaned control stations without a field-observed reference azimuth line. The base angles at the control stations or the azimuth of the first traverse leg is computed from the geometry of the traverse. Thereafter, the traverse is computed as a normal traverse. This traverse method is termed reorientation traversing. This article will statistically compare the variation in the computed coordinates when using the reorientation traversing method versus the traditional traverse method, which has either known azimuths at each end of the traverse or two previously established control stations at the termini. To make this comparison, a series of four different traverses with varying numbers of new stations were run using both the reorientation and traditional traverse methods. From these case studies, a correctly weighted least squares adjustment was performed, and a statistical test at a 0.01 level of significance was performed on the resultant coordinates. This comparison demonstrates that the two methods produce a set of coordinates that can be considered statistically the same. The results demonstrate that reorientation traversing is a valid procedure when sufficient directional control is not available in the field. [ABSTRACT FROM AUTHOR]

In order to improve the visualization efficiency of multi-GNSS satellite orbit model, a new simplified method was demonstrated and a simulation was conducted. This method includes the following three aspects: the orbit shape of satellites was altered from ellipse to circle; in the same constellation, different values of orbit semi-major axes were unified into one mean value; the values of right ascension of ascending node were clustered and renewed based on K-means algorithm. In conclusion, simulation results show that the new method can radically decrease the required number of displayed orbits, and decrease the render time of the model while the frames per second are increased. The visualization efficiency of multi-GNSS satellite orbit model is significantly improved. [ABSTRACT FROM AUTHOR]

Unambiguous tracking for Binary Offset Carrier (BOC) modulated signals' is an important requirement of modern Global Navigation Satellite System (GNSS) receivers. An unambiguous tracking method based on combined correlation functions for even/odd order sine/cosine-BOC, Composite BOC (CBOC) and Alternate BOC (AltBOC) modulated signals is proposed. Firstly, a unified mathematical formulation for all kinds of BOC modulations is introduced. Then an unambiguous tracking method is proposed based on the formulation and the idea of pseudo correlation function (PCF) method. Finally, the tracking loop based on the proposed method is designed. Simulation results indicate that the proposed method can remove side peaks while retaining the sharp main peak for all kinds of BOC modulations. The tracking performance for AltBOC is examined and the results show that the proposed method has better performance in thermal noise and long-delay multipath mitigation than the traditional unambiguous tracking methods. [ABSTRACT FROM AUTHOR]