• Marked chainage
• Track survey and topographical detail
• OHLE heights and stagger
• Clearance gauging profiles (clearRoute sco file)
• Survey control points

However, tunnel surveys present their own specific problems and demand a specialist knowledge to arrive at valid solutions. We have extensive knowledge of working in tunnel environments and know how to coordinate survey stations effectively underground, maintain survey control against tamping, survey multiple clearoute sections, detail changes in construction and arrange the appropriate site access.

Tunnel surveys are also well suited to laser scanning. For example, in an irregular rock cutting, engineers may not know specifically where the main clearance problem areas are. Therefore the survey of cross sections would be an iterative affair, involving costly site re-visits. With 3D Laser scanning, additional cross sections can be requested once the initial field work is completed: even requesting sections every half metre or less if required. Learn more….

In 2009 we acquired the Amberg GRP system FX for trolley based helical scanning; giving us the ability to gauge over 1km per hour through tunnels. This system can also collect high accuracy track geometry and absolute position data and allow quality checks for:

• Tunnel modifications
• Box Tunnel traverse, topographic survey, ClearRoute clearance SCO sections (GW Electrification project)
• Sodbury Tunnel topographic survey, ClearRoute clearance SCO profiles
• Tunnel clearance and profile checks
• Tunnel monitoring & comparisons
• Inventory surveys and assessment databases

Examples of relevant experience include:

• Severn Tunnel traverse and drainage survey
• Irregular bare rock tunnel for clearance surveys (Blaenau Ffestiniog)
• Thameslink tunnels
• Birmingham bridgeguard tunnel surveys
• Monitoring movement at Manton Tunnel and Birmingham New Street