Laser-scan system has virtual view of Stonehenge details

Experts at English Heritage are using laser scanning and high-resolution digital imaging to create a virtual rendering of Stonehenge that will show it in detail and hopefully reveal new features.

The survey will map the standing and fallen stones of Stonehenge, as well as the top of the horizontal lintels.

Despite the vast amount of archaeological activity and academic study into Stonehenge and its landscape over the centuries, relatively little is known about the lichen-covered surfaces.

A survey of these surfaces was last undertaken in 1993 using photogrammetry — a technique that combines overlapping images — to achieve a somewhat limited resolution of 2cm.

’We’re trying to capture the subtleties in the surfaces that are there now, but of course in 10, 20 years’ time they might decay. Hopefully, we can prise out any man-made carvings that are not known about already,’ said Paul Bryan, head of Geospatial Imaging at English Heritage, who is leading the project.

In the latest surveying project, the team is using a combination of laser scanning with a Z+F Imager 5010 and photogrammetry at 24 megapixels — which together will be able to resolve down to 0.5mm.

’The beauty of the laser-scan system is the immediacy of the 3D data and the speed of the data capture these days — we can capture millions of 3D points within a few minutes, it’s a very economic method of data capture,’ Bryan said.

One of the key advantages of the latest approach is the ability to integrate data sets to produce various computer-generated renderings of the monument for public understanding and interpretation, as well as scientific study.

’All of the data is being captured in the spatial coordinates system using GPS and the way that the scan data is processed will allow it to be merged with the photogrammetrically derived data so you get seamless integration of the data sets,’ Bryan said.

The data capture itself should be finished by the end of this week, while the post-production analysis will take perhaps several months depending on techniques that can be brought to the data.  

’The really interesting thing is introducing the likes of virtual light, replicating the effect of the sun as it’s moving round, so if you shine a light very obliquely you can see various things picked out. By doing this virtually you’ve got an infinite number of raking light images and by animating those together you can start to see new features that have not been seen before,’ Bryan said.

The project is being undertaken by English Heritage with the assistance of Greenhatch Group together with Atkins Mapping and Archaeo-Environment.