Aldwych is a central part of London, where life never stops. TopoCrew was tasked with surveying an underground service tunnel and the surface in the same system to enable planning of the relocation of the tunnel service access as its current location obscures the pedestrian traffic if opened.
Project Snapshot
Project type: Laser scanning
Client: FM Conway
Borough: City of Westminster
Location: Aldwych
Instruments: Leica RTC360 Laser Scanner + Leica Total Station
Deliverables: 3D model to be used in BIM environment
Objectives and Challenges
The biggest challenge for this project was establishing the reference network. To get control points down to the service tunnel, our team had to triangulate through the surface and the tunnel to provide the required amount of control points for the scanner. The connection between the surface and the underground areas was established through service entrances and smoke outlet openings. We also surveyed the cellars of Bush House and King’s College using the same technique.
The main goal of this survey was to produce a BIM model, a digital twin of the surface and underground areas to enable the planning of the relocation of the service tunnel entrance. We used our Leica RTC360 laser scanner combined with traditional total station measurements to achieve the required results and accuracy.
TopoCrew’s Approach
After carefully inspecting the site, our team built a surface control point network and used the two available entrance shafts to project down the underground station points from the surface to establish connection. The tunnel was connected to a series of skylights which our team opened and could use to measure the same reference points from street level and from the tunnel to increase network accuracy.
The scanning was carried out on the surface first then we moved to the underground parts. The distance between scanning stations was 10m on average to maintain the point cloud density for modelling and extraction tasks.
Results and Project Impact
Using our service the client could plan the relocation of the shafts in an accurate and highly visual way. Our partner could utilise the advantages of the BIM approach, as we laid the basic plan and the whole execution can be tracked in a BIM system allowing the client to track the cost and the whole process in a detailed 3D view, where all participants could access the information they need.
Conclusion
This project highlights our team's capabilities of measuring complex situations where above and underground scenarios are present. The complex survey techniques are part of our everyday life to complete challenging projects with the tools available. The clients usually request CAD drawings, but our experts can deliver 3D models for BIM systems also. Our team is prepared for everything, ready for challenges!