TULLOCH Engineering was contracted to provide a complete engineering survey of six Metrolinx railway commuter corridors originating from Union Station in Toronto, Canada. The Electrification project is one Metrolinx’s largest projects valued at $4 billion. TULLOCH used a unique combination of mobile LiDAR, static LiDAR, and conventional infill ground survey to complete the project. LiDAR, which stands for Light Detection and Ranging, is a surveying method that measures distance to a target by illuminating that target with a laser light. Using LiDAR technology provided significant advantages to the Electrification Project over using convention ground survey techniques.
An initial requirement for Metrolinx Electrification project is an up to date engineering survey to enable the preliminary engineering design. Our survey project involves surveying approximately 170 miles of railway corridor for six GO Transit tracks originating from Union Station in downtown Toronto. Our mobile LiDAR survey system was mounted on a GO Transit hi-rail truck; with most of the surveying occurring at night due to the heavy train traffic and since LiDAR is an active sensor.
TULLOCH provided a unique hybrid surveying approach, using mobile LiDAR surveying to collect all the visible features in the corridor, followed by conventional ground surveys to fill in missing features obscured from the LiDAR system’s field of view and static LiDAR surveys for some of the bridges inaccessible with mobile LiDAR. This is the first time Metrolinx has contracted an engineering survey using these multiple survey technologies. This survey approach reduces delivery timelines, limits track disruptions, and greatly improves safety.
A major advantage of mobile LiDAR surveying for the GO-Transit rail corridors is that collection can occur at night when train activity is low and in a fraction of the time it takes to survey using conventional ground crews. This enabled project schedules to be advanced, as base mapping was completed in about 60% of the normal time required for the engineering survey. Using mobile scanning on the tracks reduced safety risks associated with on track field surveys. In addition, the resultant LiDAR point cloud can be revisited in the office, and additional features and critical information picked up without having to send field crews back to do so. The homogeneous nature of the point cloud, combined with the conventional in-fill survey provides a rich, full feature data set that can be used at various stages in the engineering design process.