3D laser scanning
St Stephen’s Towers, Norwich
Overcoming on-site challenges to deliver high quality survey data
Survey Solutions was approached by its client for a proposal to undertake a full measured building survey of two well-known office blocks in Norwich. The ambitious multi-million-pound project aimed at transforming the two former towers in the heart of the city centre into flats for around 700 students. The survey formed an integral part of the scheme and provided the planners and designers with vital information to progress the project.
Each building consisted of eight floors and they were linked by a connecting walkway. The client specification included floor plans, roof plans, elevations, cross sections and a full 3D Revit model.
Although the buildings were of a significant size, in principle the survey should have been relatively straightforward to complete. However the survey had to be undertaken at the same time as the demolition contractor was stripping out the inside of the building and Survey Solutions only had access to the individual floors on an ‘ad hoc’ basis as and when the clearance was complete and not always in a logical order.
When each floor became available, before the surveyors could start to capture data with the 3D laser scanner, a control network of datums needed to be established from carefully-positioned control points located outside of the towers. The scan data was then registered, and a point cloud produced.
From the resulting point cloud, a 3D Revit model was created on a floor by floor basis with the model being added to after each visit. The Revit model was produced in accordance with the client’s BIM specification and gave them the information they required to redesign the building in line with the customer’s specification.
Every city centre development comes with logistical difficulties that are not associated with more rural areas. These difficulties were made more problematic because the towers were constructed on top of existing third party-owned retail units, resulting in a very small site area to work with. As the project progressed, the surveyors faced more and more challenges. These included an array of different contractors working and occupying the site, control datums being obscured and/or destroyed and the biggest of all, both towers being encased by scaffolding and wrapped in protective sheeting.