Tunnel inspection in Finland: Thermography, Clearance Check, Crack Detection



Finnish railways

Task definition

Scan of all railway tunnels of the Finnish railways

  • Visual Image scan for crack detection and damage mapping
  • Thermography for detection of moisture and water ingress
  • 3D scan for clearance check and clearance mapping


  • Recording with the TS3 tunnel scanner
  • Total length 40 km


The project in detail

In four measurement campaigns between 2007 and 2011, nearly all the railway tunnels of the Finnish railways were scanned.

This included the tunnels from the Vuosaari Harbour Project, such as Finland’s longest tunnel — the 13.5 km long Savio Tunnel. The scanner recordings and the subsequent evaluation of the data pursued a range of objectives:

  • Survey of the tunnel
  • Analysis of the existing clearance space
  • Analysis of the tunnel structures
  • Final inspection of new structures


The measurements had to be carried out without disrupting the normal passenger transport, so the measurement runs were mostly performed during the nightly breaks in operation.

A combination of a locomotive and a flat wagon was chosen as the measurement vehicle. The SPACETEC measurement vehicle with the control and recording electronics was mounted on the flat wagon.

The scan head was mounted on a support such that it had an unobstructed 360° view and was positioned in the centre of the tunnel profile.

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The processed scanner data was delivered to the client together with a customised version of the Tunnel Info software which facilitates the oversight of the many tunnel sections.

The data analysis was handled by our project partners in Finland, for which Finnish versions of all the SPACETEC evaluation software programs were created.

Tunnel Inspector was used as a mapping tool and the table of results was adapted to the requirements of Finnish State Railways.

The following data samples display the image and thermography recordings side by side. The thermography clearly shows the heated drainage pipes and the wet areas.