TRain

GNSS Signals for Numerical Weather Prediction and Galileo HAS Train Positioning

Short Description

In 2016, the Austrian Federal Railways (ÖBB) started to equip their fleet of trains with multi-GNSS receivers with the aim of online-positioning. In 2019 more than 500 vehicles are already equipped with such single-frequency receivers, providing decimetre accuracy positioning of the fast-moving traction vehicles through RTK-positioning and referencing to the EPOSA correction service. In parallel, the receivers also allow to store raw GNSS observation data of all train travels within a period of up to three weeks.

For the proposed project TRain, ÖBB provides a subset of this GNSS data for research purposes and allow therefore a thorough investigation of the offered synergies. The two main goals of the project, namely the use of the raw GNSS data for numerical weather predicition and the investigation of the positioning accuracy with single-frequency (SF) data and the meanwhile built-up Galileo CS High Accuracy Service (HAS), are united in the acronym (TRain).

Starting point for the present project is preliminary work carried out at the Department of Geodesy and Geoinformation in cooperation with ZAMG, dealing with tropospheric parameter estimation from dual-frequency (DF) observations of a GNSS reference station network and the assimilation of these parameters into a numerical weather prediction (NWP) model. Currently, Zenith total Delay (ZTD) estimates from 35 stations are available on an hourly basis, which are included in operational forecasts of ZAMG since November 2019 and are also made available in the course of the European EGVAP program.

TRain now goes far beyond the concept described above, as trains traveling on railways in the federal reserve of Austria shall be used as permanently moving meteorological sensors. The main benefit of using train data is the much denser spatial (and possibly also temporal) resolution due to the large number of sensors. They travel through different height regions and weather systems and therefore are predestined to investigate small-scale phenomena which are currently hard to represent in NWP.

In the course of this project the basic knowledge on data processing and estimation of tropospheric parameters from highly-kinematic sensors (up to 120 km/h) with sufficient accuracy shall be established. First investigations on the topic have already shown the possibility of deriving reasonable results, which were presented at the ESA Galileo-Science conference in Zurich in September 2019 (Aichinger-Rosenberger, 2019).

One of the main critical points will be the ionospheric correction of the SF data, which will require a high-quality model to deal with. Problems concerning (near) real-time data availability/transfer using e.g. a cloud infrastructure shall be tackled in the last part of the project.

With the end of 2020, the Galileo High-Accuracy Service (HAS) will become operational. The HAS delivers the latest orbit and clock corrections through the Galileo Service Center (GSC), which broadcasts information by means of up to 20 connected Galileo satellites on a regular basis. These corrections are useful information for users operating Precise Point Positioning (PPP) algorithms for positioning.

Starting with the raw GNSS observations mentioned above, a reliable positioning accuracy for fast-moving train vehicles will be assessed in TRain. Moreover, conclusions on the influence of natural and artificial obstructions on the availability of HAS shall be drawn and the HAS service shall be tested as a potential backup system for short-time failure of the RTK reference network.

Project Partners

Coordinator

TU Wien - University of Technology Vienna

Project partner

Central Institute for Meteorology and Geodynamics (ZAMG)

Contact Address

TU Wien - University of Technology Vienna
Karlsplatz 13
A-1040 Vienna
Web: www.tuwien.at