s the amount of cargo moved by rail continues to grow, railways
face an increasing need for accurate measurements on track
alignments and locations for engineering, construction and
geographic information systems (GIS). The demand comes from tighter
track tolerances and new regulations for Positive Train Control (PTC) as
well as maintenance and upgrades. And as windows for track access for
maintenance continue to shrink, railway operators must gather more
information in shorter periods of time.
Railways have several approaches to gather spatial information. Many
agencies utilize airborne or terrestrial LiDAR to acquire high-volume
information. While LiDAR works well for general locations (including
PTC), it can’t match the precision and detail produced by trained field
crews collecting track data on the ground. For these ground-based
surveys, advanced technology is producing significant increases
in efficiency and productivity.
In California, Cinquini & Passarino, Inc., (CPI) uses a Trimble GEDO CE
system to provide track measuring services. The system consists of a
small trolley containing tilt and gauge sensors, Trimble GNSS or total
station for positioning, a power supply and supporting electronics.
Moving at walking speed, the GEDO system collects essential data:
track location, vertical profile, gauge and superelevation at specified
intervals. The data are stored in a Trimble TSC3 controller.
Under a contract from Parsons Transportation Group, CPI conducted a
survey on 84 km (52 mi) of track in central California. The work called
for location of track centerline, switches and frogs, derails, roadway and
pedestrian crossings, signage, wires and tunnel portals. Busy rail traffic
forced the crews to work only between midnight and 4:00 a.m. Using
two GEDO trolley crews, CPI collected data for 8 to 13 km (5 to 8
miles) of track each night. Over the course of the survey, they collected
more than 120,000 points, with each point automatically referenced to
track centerline and top-of-rail elevation.
CPI crews also collected information for the Sonoma Marin Area Rail
Transit District (SMART). Needing precise location of existing track to
design a new bridge, CPI used the Trimble GEDO trolley to meet design
engineers’ request for detailed top-of-rail information, with accuracy of
3 mm (1/8 inch) or less at 8-m (25-ft) intervals. By using the trolley system,
CPI could provide data every 3 m (10 ft) with no increase in cost.
CPI’s experience has demonstrated that the Trimble GEDO system is
well suited for collecting the precise information needed for design,
engineering and maintenance of North American railways. Because
the GEDO system can collect data with a precision of 3 mm (1/16 in)
or better, it can be used on track classes ranging from low-speed Class 1
up through Class 9 high-speed track for freight and passenger trains.
Railways Need Accurate Information on Their Tracks and Facilities.
Here’s How Track Measuring Systems are Filling the Need.