Laser Scanning and Rock Art

This is a text from part of a short presentation given to the April 2004 Rock Art Symposium hosted by the British Academy other material from the presentation can be found at the Archaeoptics website

The Wessex Archaeology IT Section has a remit to explore the opportunities offered by new technologies and how they can be applied to archaeology and heritage management.

We set out to try to understand the capabilities and limitations of laser scanners in the hope of developing methodologies and strategies to make the best use of the technology. Perhaps more importantly we wanted to look at how we could use the products of laser scanning – point clouds - in archaeological analysis and interpretation.

You have seen the potential of the technology. I would like to offer a few thoughts on the practicalities of using it. The three main barriers to the widespread use of laser scanning in archaeological monitoring operations are acceptance, available expertise and cost.

Certainly in the UK, acceptance is growing. There is an awareness of the potential of laser scanning and hopefully we have demonstrated that particularly with carved material, a surface based record has advantages over line based records. An important development is the work being done by English Heritage the ADS and others in developing standards for the archive of the large data sets involved in scanning.

On the question of expertise we think it is important to establish what the role of the archaeologist or heritage manager in the laser scanning process?

Scanner operation requires quite some skill if the best results are to be obtained. There are questions of lighting and of the method by which scans are referenced to each other and the real world. Our feeling is that using the services of scanning bureaux is currently the most cost effective way to complete the capture phase of the process and depending on the

While we do feel that it is important that archaeologists need to be able to intelligently discuss the specifications for a scan with a contractor it is most important that they can competently analyse the results. Inevitably this does mean investing in the software and training.

Laser scanners are expensive pieces of equipment and need to be kept very busy if they are to provide good value for money in comparison to other equipment. There are few heritage organisations who could currently maintain such use levels. There are various university departments who have access to equipment but there are usually problems with them undertaking anything other than small scale experiments.

Naturally we therefore turn to scanning contractors who frankly terrify the heritage manager with rates around the £1k per day.

We have explored three different strategies to facilitate the use of laser scanning.

In research and experimental work it is still possible to partner with scanner manufacturers and scanning contractors and obtain preferential rates if not free use of laser scanners. We are fortunate in that the public relations potential of Archaeology and Heritage is still high. The scanning market is maturing fast however and commercial companies are likely to find such relationships less interesting.

In our development control work we have found that the holistic nature of laser scan data means that there is potential to resell data derived from a scan undertaken for heritage management purposes to surveyors, architects and even the marketing men. Apart from visualisations for interpretation centres this seems difficult to apply to rock art and will never provide a source of funding for long term monitoring.

Scanning historic fabric is not an attractive prospect for most contractors, access is usually difficult if not downright uncomfortable, client expectations are typically very high and the volume of scans compared to mobilisation costs are relatively low.

It is our belief however that the larger curators could establish capture schedules of their holding which could be offered as attractive contracts to commercial operators.

Our aim for the future is to continue our experimentation into applying analytical and interpretative techniques to laser scan point clouds. .

It may be that laser scanners will make it possible to look at archive sources such as casts to help gauge erosion rates and morphometric analysis of the changing profile of carvings holds some promise.

We currently have little evidence of the rate of erosion of rock art. We can be sure it is in progress and the evidence from Stonehenge is that at the moment laser scanning can rescue information on the most ephemeral of features. How soon this information will be lost forever we cannot say. Surely this is reason enough for us all to press for a widespread, integrated, properly funded programme of rock carving scans.