| DIBIT, based in Mils, Austria has developed high-tech measurement systems for full surface three-dimensional recording and evaluation of geometric and thematic data using special scanners. Digital image measuring technology using the DIBIT tunnel scanner can be applied to recording, monitoring, controlling, documentation and quality assurance of construction. Similarly, the DIBIT geo scanner monitors and checks geological formations. Ongoing creation of tunnelling project databases by DIBIT will assist all stages of tunnel construction and use, prolonging the lifespan of the structures and reducing their cost of maintenance. |
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The DIBIT tunnel scanner is a photogrammetric measurement system for the documentation of underground construction and tunnel advance. The recording system comprises a field computer and two CCD cameras, which, in combination with geodetic determination of the camera positions, deliver digital stereoscopic images of the tunnel surface. From these images, the 3D coordinates of the tunnel profile are calculated with an accuracy of +/-10 mm, to form the basis from which profiling and deformation can be calculated. These can then be visualised in a full area, or in any selected cross-section. |
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The scanner comprises a tripod stand, field computer, and sturdy carbon fibre frame with two CCD cameras and three surveying targets. The targets are positioned by a motorised theodolite, which is controlled automatically via radio modems from the recording device. The DIBIT software facilitates the recording process, and storage of image and position data. The tunnel surface is illuminated by high performance halogen headlamps. Scanning is normally carried out immediately after the face mucking operation, before arches and mesh are installed, and takes around 10 minutes to complete. |
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The recorded data are transferred to an office PC, where the evaluation software calculates the 3D coordinates of all image points in a half-centimetre grid, and creates rectified images related to the nominal geometry. An analysing module helps present the results and prepare them for additional applications. Calculations can be made for the tunnel profile, shotcrete or concrete thickness, deformation, shotcrete quantity and rebound, and the 3D orientation of relevant geological features such as stratification and fissures. The results from scanning can be presented in three ways: as a profile section; as an ortho image; or in numerical terms. |
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Advantages when using the DIBIT tunnel scanner are: short recording time; ease of handling by a single person; sturdy construction; accurate results; rapid evaluation; and multiple options for clear presentation of the results. Calculated average savings from controlling large tunnel profiles using the DIBIT scanner are: €87,500/km from reduced overprofile; €60,000/km from less shotcrete; and €20,750/km for profiling and recording. DIBIT tunnel scanners have been used on highway, metro and railway tunnels in Austria, Switzerland, Germany, Denmark, Taiwan, US, UK and Czech Republic. |
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DIBIT
Messtechnik GmbH, Gewerbepark 3, A-6068 Mils, Austria © tunnelbuilder ltd |
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