Instantaneous GPS/Galileo/QZSS/SBAS Attitude Determination: A Single-Frequency (L1/E1)Robustness Analysis under Constrained Environments

The augmentation of new global navigation satellite systems (GNSS) to existing GPS enhances the availability of satellite based positioning, navigation, and timing (PNT) solutions. Among existing systems, the European Galileo system, the Japanese quasi-zenith satellite system (QZSS), and satellite based augmented systems (SBAS) share at least one frequency (L1/E1) with GPS. In this contribution we analyse the robustness of single-frequency instantaneous carrier-phase attitude determination using data from some or all of the four systems GPS/Galileo/QZSS/SBAS. The performance of the constrained (C)-LAMBDA method is studied under various satellite deprived environments and compared to that of the standard LAMBDA method, using L1/E1 data that was observed for ten days at Curtin University, Perth, Australia. The results demonstrate the enhanced robustness that combinations of the four systems bring to single-epoch single-frequency attitude determination

IRNSS/NavIC Single-Point Positioning: A Service Area Precision Analysis

The Indian Regional Navigation Satellite System (IRNSS) has recently (as of May 2016) become operational. The system has been developed with the objective of offering positioning, navigation, and timing (PNT) to users in its two service areas, covering the Indian landmass and the Indian Ocean, respectively. It is the goal of this contribution to provide further insight into the full-constellation L5 pseudorange single-point positioning (SPP) capabilities of the system. A detailed dilution of precision (DOP) analysis of its two service areas, including the identification, in location and time, of poor receiver-satellite geometries is provided. It is hereby demonstrated how the impact of some of these poor receiver-satellite geometries can be mitigated by means of height-constraining. An overview and analysis of the SPP precision is also provided including easy-to-use representative day-averaged values for a grid of locations covering the two service areas

IRNSS stand-alone positioning: first results in Australia

The Indian Regional Navigation Satellite System (IRNSS) currently under development is expected to reach full operational capability before 2017. As a large part of the Australian continent lies in IRNSS’s service area, it is important to gain an understanding of its navigational potential and actual positioning capabilities for Australian users. The goals of this contribution are therefore to provide insight into IRNSS, to demonstrate its current positioning performance using actual L5 pseudorange tracking data, and to analyse its expected positioning performance for when the system is fully operational. As such this contribution provides the very first results of the IRNSS stand-alone positioning capabilities over Australia

Instantaneous GPS-Galileo attitude determination: single-frequency performance

New and modernized global navigation satellite systems (GNSSs) are paving the way for an increasing number of applications in positioning, navigation, and timing (PNT). A combined GNSS constellation will significantly increase the number of visible satellites and, thus, will improve the geometry of observed satellites, enabling improvements in navigation solution availability, reliability, and accuracy. In this paper, a global positioning system (GPS) +Galileo robustness analysis is carried out for instantaneous single-frequency GNSS attitude determination. Precise attitude determination using multiple GNSS antennas mounted on a platform relies on successful resolution of the integer carrier-phase ambiguities. The multivariate-constrained least squares ambiguity decorrelation adjustment (MC-LAMBDA) method has been developed to resolve the integer ambiguities of the nonlinearly constrained GNSS attitude model that incorporates the known antenna geometry. In this paper, the method is used to analyze the attitude determination performance of a combined GPS +Galileo system. Special attention is thereby given to the GPS and Galileo intersystem biases (ISBs).The attitude determination performance is evaluated using GPS/Galileo data sets from a hardware-in-the-loop experiment and two real-data campaigns. In the hardware-in-the-loop experiment, a full GPS/Galileo constellation is simulated, and performance analyses are carried out under various satellite-deprived environments, such as urban canyons, open pits, and other satellite outages. In the first real-data experiment, single-frequency GPS data, combined with the data of Galileo in-orbit validation element (GIOVE) satellites GIOVE-A/GIOVE-B (the two experimental Galileo satellites), are used to analyze the two constellation attitude solutions. In the second real-data experiment, we present the results based on single-frequency data from one of the Galileo IOV satellites, combined with the data of GIOVE-A and GPS. We d- monstrate and quantify the improved availability, reliability, and accuracy of attitude determination using the combined constellation

Satellite-clock modeling in single-frequency PPP-RTK processing

The real-time kinematic precise point positioning (PPP-RTK) technique enables integer ambiguity resolution by providing singlereceiver users with information on the satellite phase biases next to the standard PPP corrections. Using undifferenced and uncombined observations, rank deficiencies existing in the design matrix need to be eliminated to formestimable parameters. In this contribution, the estimability of the parameters was studied in single-frequency ionosphere-weighted scenario, given a dynamic satellite-clock model in the network Kalman filter. In case of latency of the network corrections, the estimable satellite clocks, satellite phase biases, and ionospheric delays need to be predicted over short time spans. With and without satellite-clock models incorporated in the network Kalman filter, different approaches were used to predict the network corrections. This contribution shows how the predicted network corrections responded to the presence and absence of satellite-clock models. These differences in the predicted network corrections were also reflected in the user positioning results. Using three different 1-Hz global positioning system (GPS) single-frequency data sets, two user stations in one small-scale network were used to compute the positioning results, applying predicted network corrections. The latency of the network products ranges from 3 to 10 s. It was observed that applying strong satellite-clock constraints in the network Kalman filter (i.e., with the process noise of 1 or 0.5mm per square root of second) reduced the root-mean squares (RMS) of the user positioning results to centimeters in the horizontal directions and decimeters in the vertical direction for latencies larger than 6 s, compared to the cases without a satellite-clock model

Multi-GNSS PPP-RTK: From large- to Small-Scale networks

Precise point positioning (PPP) and its integer ambiguity resolution-enabled variant, PPP-RTK (real-time kinematic), can benefit enormously from the integration of multiple global navigation satellite systems (GNSS). In such a multi-GNSS landscape, the positioning convergence time is expected to be reduced considerably as compared to the one obtained by a single-GNSS setup. It is therefore the goal of the present contribution to provide numerical insights into the role taken by the multi-GNSS integration in delivering fast and high-precision positioning solutions (sub-decimeter and centimeter levels) using PPP-RTK. To that end, we employ the Curtin PPP-RTK platform and process data-sets of GPS, BeiDou Navigation Satellite System (BDS) and Galileo in stand-alone and combined forms. The data-sets are collected by various receiver types, ranging from high-end multi-frequency geodetic receivers to low-cost single-frequency mass-market receivers. The corresponding stations form a large-scale (Australia-wide) network as well as a small-scale network with inter-station distances less than 30 km. In case of the Australia-wide GPS-only ambiguity-float setup, 90% of the horizontal positioning errors (kinematic mode) are shown to become less than five centimeters after 103 min. The stated required time is reduced to 66 min for the corresponding GPS + BDS + Galieo setup. The time is further reduced to 15 min by applying single-receiver ambiguity resolution. The outcomes are supported by the positioning results of the small-scale network

Integrated GNSS Attitude Determination and Positioning for Direct Geo-Referencing

Direct geo-referencing is an efficient methodology for the fast acquisition of 3D spatial data. It requires the fusion of spatial data acquisition sensors with navigation sensors, such as Global Navigation Satellite System (GNSS) receivers. In this contribution, we consider an integrated GNSS navigation system to provide estimates of the position and attitude (orientation) of a 3D laser scanner. The proposed multi-sensor system (MSS) consists of multiple GNSS antennas rigidly mounted on the frame of a rotating laser scanner and a reference GNSS station with known coordinates. Precise GNSS navigation requires the resolution of the carrier phase ambiguities. The proposed method uses the multivariate constrained integer least-squares (MC-LAMBDA) method for the estimation of rotating frame ambiguities and attitude angles. MC-LAMBDA makes use of the known antenna geometry to strengthen the underlying attitude model and, hence, to enhance the reliability of rotating frame ambiguity resolution and attitude determination. The reliable estimation of rotating frame ambiguities is consequently utilized to enhance the relative positioning of the rotating frame with respect to the reference station. This integrated (array-aided) method improves ambiguity resolution, as well as positioning accuracy between the rotating frame and the reference station. Numerical analyses of GNSS data from a real-data campaign confirm the improved performance of the proposed method over the existing method. In particular, the integrated method yields reliable ambiguity resolution and reduces position standard deviation by a factor of about 0.8, matching the theoretical gain of √3/4 for two antennas on the rotating frame and a single antenna at the reference station

Positioning Eye Fixation and Vehicle Movement: Visual-motor Coordination Assessment in Naturalistic Driving

In recent years, many driving studies in the traffic safety literature have undertaken error assessments of driver behaviour. However, few studies have been able to analyse the detailed individual vision and motor behaviours of drivers, due to the lack of reliable data and available technologies. Therefore, little is currently known about drivers' visual-motor coordination involving the use of visual information to regulate their physical movements. This research sets-up a technical framework to investigate on-road drivers' visual-motor coordination via vision tracking and vehicle positioning. The driving behaviour and performance were recorded and analysed using Eye Movement Tracking, Global Navigation Satellite System (GNSS) and Geographic Information Systems (GIS). The eye tracker recorded eye fixations and duration on video images to analyse the visual pattern of individual drivers. Real-time kinematic (RTK) post-processing of multi-GNSS generated vehicle movement trajectory at centimetre-level accuracy horizontally, which encompasses precise lateral positioning, speed and acceleration parameters of driving behaviours. The eye fixation data was then geocoded and synchronised with the vehicle movement trajectory in order to investigate the visual-motor coordination of the drivers. A prototype of implementation of the framework focusing on complex U-turn manoeuvre at a roundabout in five older drivers was presented in this paper. The visualisation of spatial-temporal patterns of visual-motor coordination for individual drivers allows for a greater insight to behaviour assessment. The on-road driving test in this study has also demonstrated a discriminant and ecologically valid approach in driving behaviour assessment, which can be used in studies with other cohort population

GLONASS CDMA L3 ambiguity resolution and positioning

A first assessment of GLONASS CDMA L3 ambiguity resolution and positioning performance is provided. Our analyses are based on GLONASS L3 data from the satellite pair SVNs 755-801, received by two JAVAD receivers at Curtin University, Perth, Australia. In our analyses, four different versions of the two-satellite model are applied: the geometry-free model, the geometry-based model , the height-constrained geometry-based model, and the geometry-fixed model. We study the noise characteristics (carrier-to-noise density, measurement precision), the integer ambiguity resolution performance (success rates and distribution of the ambiguity residuals), and the positioning performance (ambiguity float and ambiguity fixed). The results show that our empirical outcomes are consistent with their formal counterparts and that the GLONASS data have a lower noise level than that of GPS, particularly in case of the code data. This difference is not only seen in the noise levels but also in their onward propagation to the ambiguity time series and ambiguity residuals distribution

Tackling Inhomogeneous Open Boundary Designs by the Finite-Element Method

In the course of designing and analyzing electromagnetic devices, open boundary field problems often need to be solved. The mapping of the infinite exterior of a finite circular region onto the interior of that closed circular region has emerged and established itself as one of the best methods. However, as a result of the work done in the past in solving homogenous exterior regions, this paper shows that thismapping method has been mistakenly taken to apply only when the exterior consists of air or, at best, some other homogeneous medium. This paper validates the method for problems with uniformly inhomogeneous exterior regions and makes possible the solution of a new class of problems by this powerful method