The author outlines the methods used in surveying the overall route of the 60 km channel tunnel project. Early proposals suggested a route which would have resulted in a tunnel alignment lying in the upper beds of the lower chalk or even in the middle chalk. This was later realigned to keep the route within the chalk marl at the bottom of the lower chalk. In order to increase the accuracy of the survey work and simplify site work it was found necessary to devise a local grid co-ordinate system known as the channel tunnel grid based on the 1951 cross channel survey. This local grid has an interface between the respective national surveys and also offers the ability to convert co-ordinates from one system to another. Although accuracies of individual measurements and the tunnelling scheme as a whole must be of the highest order to achieve reasonable junctions, the service tunnel to be driven as a pilot tunnel will allow the survey link to be completed and the drive lines adjusted accordingly. The use of gyrotheodolites to provide an independent check of bearing to within + or - 20 sec of arc is discussed. /TRRL/

  • Availability:
  • Corporate Authors:

    Morgan-Grampian Limited

    30 Calderwood Street
    London SE18 6QH,   England 
  • Authors:
    • HULME, T W
  • Publication Date: 1974-9

Media Info

  • Features: Figures; Photos; References;
  • Pagination: p. 43-46
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00125112
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Nov 18 1975 12:00AM