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The ARCHAEOLOGIST - English Late-Medieval timber-framed ...

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Laser scanning at<br />

Murray Cook<br />

Rosslyn Chapel<br />

Rosslyn chapel, near Edinburgh,<br />

one of the finest surviving late<br />

collegiate churches in Scotland,<br />

is renowned for the intricacy of<br />

its carved stonework – most<br />

famously and spectacularly the<br />

Apprentice Pillar: an exceptional<br />

work of spiralling foliate carving,<br />

interweaving Christian and<br />

Scandinavian traditional<br />

iconography. Founded in 1446<br />

by Sir William Clair, the chapel<br />

is one of the finest examples of<br />

pre-Reformation ecclesiastical<br />

architecture in Scotland,<br />

incorporating a range of structural<br />

features regarded as iconic of<br />

the Scottish late medieval style.<br />

Recent historical research<br />

indicates that it was built around<br />

the same time as Glasgow<br />

Cathedral, perhaps by the same<br />

stonemasons and architects.<br />

Rosslyn Chapel<br />

Knights Templar and the Holy Grail<br />

Its architectural significance has long attracted<br />

visitors and in recent years their numbers have been<br />

augmented by those interested in its putative<br />

associations with the Knights Templar and the Holy<br />

Grail. <strong>The</strong> chapel’s popularity is unlikely to<br />

diminish, given its appearance in the Da Vinci Code.<br />

Increased visitor pressure is one of the threats to the<br />

structural integrity of the chapel.<br />

Settlement and erosion<br />

<strong>The</strong> chapel is sited immediately adjacent to the edge<br />

of Rosslyn Glen, one exit from the crypt now<br />

opening out on the glen side. <strong>The</strong> strata on which it<br />

is built comprise alternating layers of sands, silts<br />

and gravels with one thick band of clay. <strong>The</strong>se strata<br />

dip towards the glen, and survey reveals that the<br />

chapel has moved slightly since its construction.<br />

Settlement, erosion of its fabric and erosion of the<br />

mortar beds have contributed to the ingress of<br />

water, endangering the site. An external canopy was<br />

erected to protect the chapel while its problems<br />

could be studied and cured.<br />

As part of the conservation plan, AOC Archaeology<br />

Group undertook a detailed survey of the interior<br />

and exterior of the chapel, producing CAD drawings<br />

which will act as a baseline for the measurement of<br />

change, anthropic or natural, and provide the first<br />

full record of the site.<br />

Laser scanning<br />

With the view impeded by the canopy, recording of<br />

Rosslyn and all its extravagantly three-dimensional<br />

Eastern elevations<br />

of Rosslyn Chapel<br />

carvings presented a considerable challenge for<br />

normal EDM survey or photogrammetry<br />

techniques. <strong>The</strong> solution was to employ laser<br />

scanning. AOC’s Mensi GS100 scanner is ideally<br />

suited to the detailed medium range building<br />

survey required. As such, a detailed 3-dimensional<br />

record could be taken of the building, with<br />

millimetre-density scans taken of more intricately<br />

carved areas. By scanning from numerous angles<br />

inside and outside the building, full coverage of the<br />

structure of the chapel could be achieved, while the<br />

scaffolding canopy and other obstructions to the<br />

survey could be edited out in the post-processing<br />

stage.<br />

<strong>The</strong> point clouds produced by the scanning work<br />

were imported into a CAD environment for the<br />

production of 2D elevations. <strong>The</strong> result was a series<br />

of scaled, detailed AutoCAD drawings of all of the<br />

interior and exterior elevations of the building.<br />

Murray Cook<br />

AOC Archaeology<br />

Edgefield Road Industrial Estate<br />

Loanhead<br />

Midlothian EH20 9SY<br />

murray@aocscot.co.uk<br />

<strong>The</strong> Apprentice<br />

Pillar<br />

34<br />

<strong>The</strong> Archaeologist<br />

Summer 2006 Number 60<br />

35

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