CAT 474 & 476 Bridges

Contract value:
Topographical Surveying

As part of the works to facilitate the design of a replacement bridge deck for Intersection Bridges 474 and 476 on the Catford Loop and LCH lines, a topographical survey was required. In association with the deck replacement, the design of the permanent way and the assessment/relocation of existing services and utilities in the area was also necessary.

The works were carried out under weekend possessions with protection staff provided by Costain. Frankham Consultancy Group’s surveyors installed network permanent control stations, tied these to OS national grid co-ordinates and carried out a closed loop traverse to Network Rail survey standards. Using this control, we then surveyed the bridges and tracks using a combination of static HDS laser scanning and Amberg 3000 & 5000 on track measuring devices. (The former where only track position and offsets to structures was required, and the latter where point cloud of track data was also needed). Further details of the cess and track furniture were recorded using our robotic one man total stations. Finally a photo record and walkthrough survey was carried out.

Once back in the office, the recorded data was used to create 3D Microstation models of the bridges together with 3D topographical track surveys of the permanent way either side of the bridges and of the LCH line under Bridge 476. A Leica Truview virtual environment of the top and underside of the bridges was created from a combination of the static scan data and site photographs.