Multi-system GNSS Research Articles

ИССЛЕДОВАНИЕ ПОМЕХОУСТОЙЧИВОСТИ МУЛЬТИСИСТЕМНОГО GNSS ПРИЕМНИКА

The article presents the results of a study of the noise immunity of the ATGM336H multi-system GNSS receiver to the influence of narrow-band interference at the L1 frequency set for one of the systems (GLONASS or GPS). The review of existing works on the study of noise immunity of satellite navigation receivers is carried out. The method of conducting experiments is presented. The simulator CH-3803M was used as a signal source from navigation satellites. The analysis of the results obtained during the experiments for the formulation of narrow-band interference of various capacities via GPS and GLONASS channels is carried out.

GPS\u2009+\u2009Galileo\u2009+\u2009BeiDou precise point positioning with triple-frequency ambiguity resolution

Along with the rapid development of GNSS, not only BeiDou, but also Galileo, and the newly launched GPS satellites can provide signals on three frequencies at present. To fully take advantage of the multi-frequency multi-system GNSS observations on precise point positioning (PPP) technology, this study aims to implement the triple-frequency ambiguity resolution (AR) for GPS, Galileo, and BeiDou-2 combined PPP using the raw observation model. The processing of inter-frequency clock bias (IFCB) estimation and correction in the context of triple-frequency PPP AR has been addressed, with which the triple-frequency uncalibrated phase delay (UPD) estimation is realized for real GPS observations for the first time. In addition, the GPS extra-wide-line UPD quality is significantly improved with the IFCB correction. Because of not being contaminated by the IFCB, the raw UPD estimation method is directly employed for Galileo which currently has 24 satellites in operation. An interesting phenomenon is found that all Galileo satellites except E24 have a zero extra-wide-lane UPD value. With the multi-GNSS observations provided by MGEX covering 15 days, the positioning solutions of GPS + Galileo + BeiDou triple-frequency PPP AR have been conducted and analyzed. The triple-frequency kinematic GNSS PPP AR can achieve an averaged 3D positioning error of 2.2 cm, and an averaged convergence time of 10.8 min. The average convergence time can be reduced by triple-frequency GNSS PPP AR by 15.6% compared with dual-frequency GNSS PPP AR, respectively. However, the additional third frequency has only a marginal contribution to positioning accuracy after convergence.

Millimeter-level ultra-long period multiple Earth-circling surface waves retrieved from dense high-rate GPS network

High-rate GPS networks have proven to be capable of continuously recording strong ground motion, which is valuable for studying earthquake rupture processes and seismic hazard mitigation. Previous studies of high-rate GPS usually resolved dynamic ground displacements of some major seismic phases stronger than a few millimeters. In this study, we explore the feasibility of retrieving much weaker ground motions (sub-millimeter) in long duration records by stacking high-rate GPS network. We processed data of the 2011 Tohoku-Oki earthquake recorded by more than 600 high-rate GPS stations of the Plate Boundary Observatory (PBO) and analyzed kinematic displacement results with seismic array methods. From these high-rate GPS seismograms, we identified abundant seismic phases, not only including clear body waves such as multiple S waves (S, SS, SSS, SSSS traveling along minor/major great circle arc, and SSSSSS beyond 360 degrees), but also the R1–R5 Rayleigh waves and G1–G6 Love waves, some of which travel around the Earth multiple times. Many of these seismic phases have not been reported by previous high-rate GPS studies. The group velocity dispersion curves extracted from multiple earth-circling Love waves of high-rate GPS are consistent with those of broadband seismic records in the period from 150 to 600 s, which can sample the mantle structure down to top of the lower mantle, thus important for understanding interaction between upper mantle and lower mantle. So the dense high-rate GPS networks should be useful for deep mantle research as an additional valuable dataset. With the development of multi-system GNSS and the more precise modeling of error sources, high-rate GNSS data should have great potential for accurately detecting more geodynamic processes with much wider bandwidth in geoscience studies.

Development of a control system for a ballast cleaning machine using GNSS

Monitoring the geometric parameters of cutting and cleaning ballast during reconstruction and overhaul works is one of the most important tasks of ensuring high quality repair work. The paper describes a new type of automated control system to control the cutting process and the cleaning of ballast performed at major overhaul and reconstruction. This automated control system uses the data of a multisystem GNSS receiver, base Reference stations and spring-return mechanisms for installing antennas on the working body of the track machine (bar chain). Nowadays, gravel-cleaning machines have installed standard work quality control systems (depth of ballast cut and lateral slope), and other measuring control tools are also used. The disadvantages of existing technologies and instrumental testing are considered. The modern automatic control systems of various types developed by SGUPS and based on the use of global navigation systems are presented. Detailed schemes of working elements of ACS installed on the ballast cleaning machine (BCM) are presented. Algorithms to determine the depth and cross slope of the ballast cutting and control of these values are considered. The use and effectiveness of this type of ACS providing the required accuracy of work and continuous monitoring of the main quantities are substantiated.

Multifrequency algorithms for precise point positioning: MAP3

We present the new MAP3 algorithms to perform static precise point positioning (PPP) from multifrequency and multisystem GNSS observations. MAP3 represents a two-step strategy in which the least squares theory is applied twice to estimate smoothed pseudo-distances, initial phase ambiguities, and slant ionospheric delay first, and the absolute receiver position and its clock offset in a second adjustment. Unlike the classic PPP technique, in our new approach, the ionospheric-free linear combination is not used. The combination of signals from different satellite systems is accomplished by taking into account the receiver inter-system bias. MAP3 has been implemented in MATLAB and integrated within a complete PPP software developed on site and named PCube. We test the MAP3 performance numerically and contrast it with other external PPP programs. In general, MAP3 positioning accuracy with low-noise GPS dual-frequency observations is about 2.5 cm in 2-h observation periods, 1 cm in 10 h, and 7 mm after 1 day. This means an improvement in the accuracy in short observation periods of at least 7 mm with respect to the other PPP programs. The MAP3 convergence time is also analyzed and some results obtained from real triple-frequency GPS and GIOVE observations are presented.

Interoperable GPS, GLONASS and Galileo software receiver

The new and modernized GNSS navigation systems will provide various navigation services and signals for civil user. The system operators work on basic interoperability agreements which simplify multi-system navigation receiver architecture and reduce its cost. The most current GNSS signals of GPS, GLONASS and Galileo can be processed by one or several classical E-L correlators with a look up table PRN generator of a length of 10,230 chips. Most signals are processed optimally, but for some signals, like Galileo E1b and E1c or GPS L1C, this signal processor does not utilize all signal components and properties. The proposed E-L correlator was implemented to the FPGA of the experimental software GNSS receiver and was tested on the Galileo E1b, E1c, and E5a signals. The target multi-system GNSS receiver architecture based on an ExpressCard peripheral card for the standard PC computer or notebook is described herein. Up to one hundred universal correlators and signal snapshot capture unit for DSP acquisition are programmed to the receiver FPGA.

Interoperable GPS, GLONASS and GALILEO software receiver

The new and modernized GNSS navigation systems will provide various navigation services and signals for civil user. The system operators work on basic interoperability agreements which simplify multi-system navigation receiver architecture and reduce its cost. The most current GNSS signals of GPS, GLO- NASS and GALILEO can be processed by one or several classical E-L correlators with a look up table PRN generator of length 10230 chips. Most signals are processed optimally, but for some signals, like Galileo E1b and E1c or GPS L1C, this signal processor does not utilize all signal components and properties. The proposed E-L correlator was implemented to the FPGA of the experimental software GNSS receiver and was tested on the GALILEO E1b, E1c and E5a signals. The target multi-system GNSS receiver architecture based on an ExpressCard peripheral card for the standard PC computer or notebook is described in the paper. Up to hundred universal correlators and also signal snapshot capture unit for DSP acquisition are programmed to the receiver FPGA.

Implement and Analysis of a COMPASS/GPS Software Receiver

A multi-channel, multi-system and multi-frequency GNSS software receiver was developed with C++ code. The software receiver takes digital intermediate frequency (IF) data as its input. It performs acquisition, tracking and navigation solution on a standard PC with C++ programs instead of hardware. It is capable of acquisition and tracking of COMPASS B1C code and GPS L1C/A code. An IF software signal generator was developed to verify functions and performances of the software receiver. This generator can simulate the COMPASS B1(C code) and GPS L1 (C/A code) constellation signals. The outputs of the signal generator were compared with the outputs of the receiver. The results show that there is less error. The correctness of the software receiver was inspected.

Broadband convex impedance ground planes for multi-system GNSS reference station antennas

Common choke ring ground planes are known to contribute to undesirable antenna pattern narrowing in the elevation plane which is associated with difficulties of tracking low elevation satellites. Also known is the comparatively narrow frequency bandwidth of the choke grooves structure. As an alternative, using a convex impedance ground plane has been suggested for full-spectrum GNSS applications. With such ground planes a pin structure is utilized instead of choke grooves to allow a frequency bandwidth increase. A semi-spherical shape of the ground plane is shown to provide increased antenna gain for low elevation angles. Theoretical performance estimates along with experimental test data have been provided.

Precise GLONASS orbit determination within the IGS/IGLOS – Pilot Project

Abstract This paper reviews the reasons for setting up the IGS GLONASS Pilot Project and the objectives of this initiative. Then we present the operational tracking network as well as the current state of the GLONASS constellation. Afterwards, we discuss in more detail the generation and consistency of current GLONASS precise orbits based on microwave and on laser tracking data. Later on the procedure for generating the more robust combined precise GLONASS orbits is explained, accompanied by information how all the IGLOS products can be accessed. Taking into consideration the upcoming GALILEO system, IGLOS can pave the way for handling data from a multi-system GNSS.