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07 June 2016

Achieving high-accuracy geo-localization inside a 57-kilometre tunnel without GPS

In outdoor conditions, geo-localization is usually carried out with GPS data and there is no challenge to succeed in such a mission. But inside a tunnel, where GPS is not available, the task is more difficult, unless aided by the high-performance TopAxyz IMU combined with the iMAR system architecture and data fusion.

In this situation, what is needed is an autonomous navigation measurement device that will provide accurate positioning from the data analyzed. Such was the mission given to iMAR, a medium-size German company specialized in autonomous navigation, contracted by SBB, the Swiss railway network. They had to verify that continuous GSM-R reception, a core component of the ETCS (European Train Control System) infrastructure, is available all along the 57-kilometre-long Gotthard Base Tunnel between Italy and Switzerland, to guarantee train safety.

To carry out their mission, iMAR selected the Thales TopAxyz IMU (Inertial Measurement Unit) within its core navigation and localization system. The system was used inside the tunnel to deliver the position of the data measured in order to achieve certification of the GSM-R network>
At the end of the 57-kilometre tunnel, the derivation of measurements was well below 0.03%.

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