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.

Fast Tracks

Railways Need Accurate Information on Their Tracks and Facilities.

Here’s How Track Measuring Systems are Filling the Need.