TasRail, Hobart, Tasmania Australia
Laser-based clearance survey gives TasRail the green light to run the latest locomotive class on the Melba Line on Tasmania’s wild West Coast.
Tasmanian Railway Pty Ltd (TasRail) is a State government owned corporation that operates and maintains the Tasmanian rail network.
TasRail is responsible for the maintenance and operation of the former Emu Bay Railway now known as the Melba Line, a narrow gauge (3’6”) railway stretching from Burnie on the Tasmanian north coast to Melba Siding, just north of Zeehan. The Tasmanian West Coast’s mountainous terrain poses challenges for locomotives, which have to negotiate steep grades, tight curves, narrow bridges, cuttings and tunnels.
TasRail needed to define a maximum clearance profile for the Melba Line to establish if the latest ‘D Class’ 2020 Locomotive, currently running on Tasmanian East Coast lines, could also run on West Coast rail infrastructure.
Geomatic Technologies (GT) undertook a laser clearance survey of the Melba Line using its Asset Inspection and Mapping System (AIMS) mobilised onto a TasRail hyrail. GT AIMS facilitates the capture of 360º laser profiles and a continuous stream of georeferenced digital imagery.
GT AIMS was fitted and calibrated at the TasRail depot in Launceston. Additional calibration was carried out in the field at the Ring River Bridge where the bridge was measured by conventional surveying methods as well as by GT’s lasers. This information was used to verify laser calibration settings and confirmed the distances measured to centimetre accuracy over the 130 kilometre line.
Once collected, the field data was post-processed at GT’s head office in Melbourne. Track centreline coordinates were processed and distances were established from kilometre posts identified in the digital imagery. The laser orientation was calibrated using the measurements from the Ring River Bridge.
From engineering drawings supplied by TasRail a structure gauge template of the locomotive was defined through kinematic analysis based on vehicle dynamics (body roll, etc.) and track curvature. This locomotive template was then ‘pushed’ through the laser point cloud data. Encroachments found were categorised according to their location (kilometrage) and type (bridge, signal, vegetation, etc.). The digital imagery was used to establish if any encroachments were in fact vegetation and could, therefore, be excluded from the analysis.
The final deliverable to TasRail was comprised of a spatial dataset of laser data and images at each encroachment location. It was found that, in general, cuttings would not encroach on the new locomotive. However, encroachments were confirmed for the Argent Tunnel and were accurately located. Further encroachments were discovered at a bridge where the Melba Line passes under the Murchison Highway, at an old abandoned railway platform, and at locations where some landslides had occurred.
The clearance survey produced a number of outcomes for TasRail:
- The clearance reports gave TasRail confidence that the ‘D Class’ 2020 Locomotive would be compatible with the Melba Line.
- TasRail now had an accurate and up-to-date track centreline of the Melba Line.
- Delays to railway operations were minimised as data was collected at ‘line speed’.