St Alphage Tower 3D archaeological survey

MOLA’s Geomatics team laser-scanned St Alphage Tower in the City of London ahead of a development by Brookfield. The monument comprises the remains of a medieval priory and later church. Using a Leica ScanStation C10 the team laser-scanned the entire monument. The creation of models from laser-scan data allowed for high levels of detail to be presented enabling us to understand the site in ways not previously possible.

The level of detail the 3D scanner captured has enabled us to understand the tower as never before.

The scanner works by using a spinning laser beam, able to measure up to 50 thousand points per second. Scanning from several locations allowed us to quickly record the building’s surface. The scanner also records photographic data which was applied to the point cloud to generate photo-rendered 3D models.

The laser-scan data collected was merged to create a single 3D point-cloud* model of the structure, enabling us to create various products to help interpret the monument’s complex history. The locations were then tied into the Ordnance Survey National Grid using Total Station and GPS (Global Positioning Systems), to precisely locate the model. Using specialist programmes we created an accurate 3D mesh-surface model of the monument, as well as detailed 2D CAD plans and elevations.

These models can be used by historic building specialists in the future to analyse building materials, building phases and construction techniques. The mesh-models can also be used for conservation or disaster management planning; as a tool for monitoring the condition of a structure or for re-building. The data could even inform a virtual 3D reconstruction.  

*A group of points, each with an XYZ co-ordinate, which represents the external surface of an object, and that light intensity values or photographic RGB values can be applied to.