Sydney Trains, Sydney Australia

Sydney Trains uses laser survey data to optimise the locations of new 2G and 3G mobile telecommunication cables on the CityRail network

Business Challenge

Sydney Trains (formerly RailCorp New South Wales) owns, operates, and maintains the Sydney suburban rail network including the four underground lines: City Circle, Eastern Suburbs, Airport and Epping to Chatswood link.

Modern commuters expect uninterrupted access to phone and internet services when travelling. However, providing 2G and 3G mobile telecommunication services for commuters within railway tunnels represents unique challenges.

The busiest sets of tunnels on the Sydney network, the Goulburn Street to Town Hall station tunnels that link Central Station to Town Hall Station, lacked 2G and 3G mobile coverage.

Sydney Trains engineers needed to design a cable and repeater system to fit in the narrow 90 year old tunnels in a way that did not encroach on passing trains. Traditional surveying on foot would be time consuming and expensive with work having to be undertaken outside normal operating hours. Compounded with the Occupational Health and Safety risks inherent in the rail environment and with time pressing due to the scheduling of works, turned to Geomatic Technologies (GT) for help.

Services Overview

As part of a cyclic mapping program, Sydney Trains regularly collects laser data of its underground tunnel network utilising the GT Asset Inspection and Mapping System (GT AIMS) mounted on a rail inspection vehicle.

By processing the laser data GT was able to model the proposed path of the ‘Radiax’ cable, a radiating coaxial cable with regular holes tuned for the transmission of radio frequencies, through the tunnels.

By using a structure gauge template of Sydney Trains’ double-decker passenger trains, and “pushing” this through the 3D tunnel point cloud along with the proposed cable/mount arrangement, encroachments could be identified through kinematic analysis based on vehicle dynamics (body roll etc.) and track curvature.

Using this methodology, GT was able to identify any areas where minimum clearances to passing trains were exceeded allowing Sydney Trains to further optimise the cable location and/or design.


–  The clearance report generated by GT AIMS gave Sydney Trains confidence that for the most  part, passenger trains would not interfere with the proposed cable. In addition, the report  highlighted some locations where the cable would fall within the allowable 200mm clearance  from the kinematic envelope and would need to be further optimised before any installation  work could begin.

–  Using GT AIMS Laser Sydney Trains was able to get a comprehensive understanding of any  problem areas within the tunnel network in a much quicker and cost effective way than using
conventional survey teams on-site.

–  GT’s quick processing of laser data maximised the time available to Sydney Trains to revise,  plan and execute the infrastructure works.

–  Delays to train operations were minimised as data was collected at ‘line speed’.