Ionospheric Modelling using GPS to Calibrate the MWA. II : Regional ionospheric modelling using GPS and GLONASS to estimate ionospheric gradients

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Publications of the Astronomical Society of Australia (PASA), after peer review and technical editing by the publisher. The version of record is available on line at https://doi.org/10.1017/pasa.2016.22 COPYRIGHT: © Astronomical Society of Australia 2016.We estimate spatial gradients in the ionosphere using the Global Positioning System (GPS) and GLONASS (Russian global navigation system) observations, utilising data from multiple GPS stations in the vicinity of Murchison Radio-astronomy Observatory (MRO). In previous work the ionosphere was characterised using a single-station to model the ionosphere as a single layer of fixed height and this was compared with ionospheric data derived from radio astronomy observations obtained from the Murchison Widefield Array (MWA). Having made improvements to our data quality (via cycle slip detection and repair) and incorporating data from the GLONASS system, we now present a multi-station approach. These two developments significantly improve our modelling of the ionosphere. We also explore the effects of a variable-height model. We conclude that modelling the small-scale features in the ionosphere that have been observed with the MWA will require a much denser network of Global Navigation Satellite System (GNSS) stations than is currently available at the MRO.Peer reviewe

Tropospheric products of the second GOP European GNSS reprocessing (1996–2014)

In this paper, we present results of the second reprocessing of all data from 1996 to 2014 from all stations in International Association of Geodesy (IAG) Reference Frame Sub-Commission for Europe (EUREF) Permanent Network (EPN) as performed at the Geodetic Observatory Pecný (GOP). While the original goal of this research was to ultimately contribute to the realization of a new European Terrestrial Reference System (ETRS), we also aim to provide a new set of GNSS (Global Navigation Satellite System) tropospheric parameter time series with possible applications to climate research. To achieve these goals, we improved a strategy to guarantee the continuity of these tropospheric parameters and we prepared several variants of troposphere modelling. We then assessed all solutions in terms of the repeatability of coordinates as an internal evaluation of applied models and strategies and in terms of zenith tropospheric delays (ZTDs) and horizontal gradients with those of the ERA-Interim numerical weather model (NWM) reanalysis. When compared to the GOP Repro1 (first EUREF reprocessing) solution, the results of the GOP Repro2 (second EUREF reprocessing) yielded improvements of approximately 50 and 25 % in the repeatability of the horizontal and vertical components, respectively, and of approximately 9 % in tropospheric parameters. Vertical repeatability was reduced from 4.14 to 3.73 mm when using the VMF1 mapping function, a priori ZHD (zenith hydrostatic delay), and non-tidal atmospheric loading corrections from actual weather data. Raising the elevation cut-off angle from 3 to 7° and then to 10° increased RMS from coordinates' repeatability, which was then confirmed by independently comparing GNSS tropospheric parameters with the NWM reanalysis. The assessment of tropospheric horizontal gradients with respect to the ERA-Interim revealed a strong sensitivity of estimated gradients to the quality of GNSS antenna tracking performance. This impact was demonstrated at the Mallorca station, where gradients systematically grew up to 5 mm during the period between 2003 and 2008, before this behaviour disappeared when the antenna at the station was changed. The impact of processing variants on long-term ZTD trend estimates was assessed at 172 EUREF stations with time series longer than 10 years. The most significant site-specific impact was due to the non-tidal atmospheric loading followed by the impact of changing the elevation cut-off angle from 3 to 10°. The other processing strategy had a very small or negligible impact on estimated trends

New way of GNSS data dissemination within the European Plate Observing System (EPOS), Multi-GNSS through Global Collaboration

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Integrity monitoring of vehicle positioning in urban environment using RTK-GNSS, IMU and speedometer

© 2017 IOP Publishing Ltd.Continuous and trustworthy positioning is a critical capability for advanced driver assistance systems (ADAS). To achieve continuous positioning, methods such as global navigation satellite systems real-time kinematic (RTK), Doppler-based positioning, and positioning using low-cost inertial measurement unit (IMU) with car speedometer data are combined in this study. To ensure reliable positioning, the system should have integrity monitoring above a certain level, such as 99%. Achieving this level when combining different types of measurements that have different characteristics and different types of errors is a challenge. In this study, a novel integrity monitoring approach is presented for the proposed integrated system. A threat model of the measurements of the system components is discussed, which includes both the nominal performance and possible fault modes. A new protection level is presented to bound the maximum directional position error. The proposed approach was evaluated through a kinematic test in an urban area in Japan with a focus on horizontal positioning. Test results show that by integrating RTK, Doppler with IMU/speedometer, 100% positioning availability was achieved. The integrity monitoring availability was assessed and found to meet the target value where the position errors were bounded by the protection level, which was also less than an alert level, indicating the effectiveness of the proposed approach

GLASS, a Tool for Quality-Controlled GNSS Data and Products Dissemination.

International audienceEurope is covered by various networks of GNSS stations maintained by different agencies with different technical and scientific objectives. The EPOS-IP (European Plate Observing System - Implementation Phase) project aims to harmonize and standardize data collection and processing and to design and establish dedicated products and services that benefit the existence of national and pan-European infra-structures (in particular EUREF), optimized for Solid Earth Research applications. We present here the efforts carried out by the members of this group to create a distributed software architecture called GLASS, a tool for quality-controlled dissemination within the EPOS, which during the operational phase, to start in 2019, shall provide GNSS data and derived products (coordinates, velocities and strain rates) from thousands of stations in Europe region. We describe the data flows from data suppliers and analysis centers to the various EPOS data portals and the integration into the overall EPOS system. In particular we describe the quality control steps that are performed in the GNSS Data and Products, from validating the station log files, obtaining quality metrics of RINEX files and there role in monitoring the overall system strength. We also describe how time series and other GNSS products computed at several analysis centers are compared and how the detection of outliers and verification of jumps are dealt with. In terms of Data and Product Dissemination we detail the overall software and portal components, the technologies that are used and resulting API's and their descriptions in formal languages for integration into the central EPOS systems software and existing workflow. EPOS-IP is a project funded by the ESFRI European Union

GLASS, a tool for quality-controlled GNSS data and product dissemination

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