Laser Scanning Poulnabrone Portal Tomb, Ireland

poulnabrone1

The Discovery Programme was asked by the National Monuments Service (NMS) of the Department of Arts, Heritage and Gaeltacht to undertake the 3D recording and modeling of the prehistoric Portal Tomb at Poulnabrone, Co. Clare. In return the NMS kindly agreed to allow the 3D data to be included in the 3D-ICONS project.

The monument was surveyed using a Faro Focus 120 laser scanner, with the resolution set to 6.5mm at 10m. The average set-up distance was well below 10m, at around 7m ensuring the average spacing in the pointcloud would not exceed 5mm. A closed traverse of eleven set up stations around the perimeter of the monument was completed by three scans in the passage and two on top of the cap stone.

Positioning the scanning in the passage at Poulnabrone

Positioning the scanner in the passage at Poulnabrone

Careful placement of the scanning to record the top surface of the capstone

Careful placement of the scanner to record the top surface of the capstone

The data was processed in Faro Scene to register the 17 scans and geo-reference them using Irish Grid coordinates surveyed using differential GPS using the VRSnow correction system. Following that enhanced manipulation and visualisation of the data was done using Pointools Edit software, generating RGB and intensity point clouds of the data.

RGB pointcloud

RGB pointcloud

Normal shaded intensity pointcloud in Pointools Edit

Normal shaded intensity pointcloud

Working with Archaeologists at the NMS the data was used to test some theories as to how the fallen capstone may have fitted into the original design. This was done in Geomagic 12 generating surface models of the stones and testing how that may have fitted together.

Surface wrap (3D model) generated in Geomagic 12 software

Surface wrap (3D model) generated in Geomagic 12 software

Fallen capstone (blue) repositioned digitally to test original construction theory

Fallen capstone (blue) repositioned digitally to test original construction theory

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