Digital Surveys have recently completed a detailed metric laser survey
for part of the UNESCO world heritage site at Durham Cathedral on behalf
of Purcell Miller Tritton.
The survey required very dense point data to be captured of a number of key areas within the Cathedral. For anyone who doesn’t know Durham Cathedral is the greatest example of Norman architecture in England. It was begun in 1093 and largely completed within 40 years. It is the
only cathedral in England to retain almost all of its Norman
craftsmanship, and one of few to preserve the unity and integrity of its
original design.
As part of the ongoing conservation plans as well as providing a snap
shot in the time, the laser survey would be used to generate very
detailed line drawings, plans and sections of the Cathedral.
The
3d laser scanning
was carried out over 10 days at the Cathedral using a Faro Photon120
phased based laser scanner. All the scans were carried out a very high
point density and colour photography was also taken at each scanner
setup.
As the cathedral is open to the public daily a lot of the work was
carried out after hours. This provided a fantastic opportunity for the
surveyors to explorer the building and carry out the survey
uninterrupted. However the Cathedral is also known for its many ghosts
especially the monks dormitory where it is said the voices of long dead
monks can be heard talking at night. This certainly kept the team on
there toes and that area was surveyed extra efficiently.
Over 250 scans were captured and processed using Faro’s Scene software.
Scene allows for automatic target extraction and registration making it
easy to manage and process large projects. All the individual rooms were
broken down into clusters and sub clusters. This helps the software
find corresponding target more accurately without having to search every
single scan.
The project was also broken up by floor and two versions were created, one with photos and one without.
Once processed ortho rectified images of every elevation were generated.
These were created in monochrome and colour at 1:20 scales. The images
could then be used in Autocad to trace up all the detailed 2d plans and
elevations.
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