Tunnel Survey – 3D laser Scan & Clearance Profiles
Rail Tunnel Survey – 3D laser Scan & Clearance Profiles Summary:
3D laser scanning & clearance profiles for Ffestiniog, Bertheos, Pont-y-Pant, Beaverpool, Penmenrhos & Lindai rock face Welsh tunnels.
These six rock cut tunnels in North Wales were required for survey in an attempt to stabilise the structures which were sporadically dropping stone onto the track and required daily clearance. The tunnels were all surveyed at night due to difficulty of day time access and were all coordinated to the OS active network using high accuracy GPS observations – and processed using Leica GeoOffice.
A GPS baseline was traversed off the end of each tunnel in a closed network using a 1 second Leica 1100 total station. Survey stations were established at 200m intervals and these were used to observe scan station control targets. All survey theodolite traversed control was computed relative to GPS fixed stations using Starnet least squares program, with our company default settings for the instrumentation used.
The Leica HDS 3000 was used to collect scan data of the tunnels at intervals determined by the number of tracks and curve of the tunnels, Beaverpool is single track line and on a tight curve and thus had setups every 25 meters. Track survey observations were processed using n4ce by Applications in CAD.
The scan data was processed using Leica Cyclone Register and sections were drawn through the tunnels using Cyclone Model at intervals stated by the client, Mott MacDonald. In some crucial tight sections of tunnel the client was able to request 1m section intervals after an initial analysis had been completed due to the completeness of the scan data collected during the site works. 5km of tunnel was surveyed over four weeks of nights.
Rock Tunnel Survey from Severn Partnership on Vimeo.
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