Rock art: digital enhancement

Digital enhancement of carved rock art (petroglyphs) is a service which we offer to rock art teams – independent or academic – anywhere in the world.

This is a very niche specialism practiced by a very small group of people globally. Our service, led by Tom Goskar FSA, draws upon his 20 years experience digitally recording and analysing rock art in the UK. He has developed many unique methodologies to tease out even the finest details from rock art panels and produce images suitable for publication or as the basis of illustration. His practical approach has led to many interesting discoveries, and he regularly publishes his work online or in academic journals.

As well as prehistoric petroglyphs, we can also apply many of our techniques to inscriptions. We have looked at Roman milestones, early medieval memorials, medieval decorated stones and more recent gravestones with good results.

Contact us to see how we can help, or read on to learn more and see examples of our work.

Data

We can work with your existing data.

We can work with 3D datasets supplied in most common formats from research or conservation projects anywhere in the world. Our fast fibre internet connection allows us to deal with the very large file sizes often involved.

We can help you capture your own data.

We are also able to advise on how to photograph a rock art panel and once supplied with the photos, we can process them into a 3D surface remotely for you. We use SfM (Structure from Motion) photogrammetry software on a powerful computer optimised for this process.

We can also use Reflectance Transformation Imaging (RTI) for particularly challenging panels.

We supply all processed data and images back to you.

We supply all data back to the client along with metadata and paradata, along with a report, 2D images, and if required, 3D models with enhanced texture maps. The final output can be decided upon through dialogue.

Enhancing petroglyphs – techniques

There is no one-click solution to making all of the details pop out. We like to think that working with enhancing rock art benefits from an archaeologist’s eye. Data needs to be treated sensitively, and exploring a digital surface needs to be undertaken carefully to ensure that a good understanding of the rock art panel occurs. Experience teaches us how to spot natural features that may lead the eye, or indeed, digital artefacts from data processing.

We view all data using a variety of filters to help us gain that understanding, before leaping in and beginning detailed digital surface analysis of rock art panels.

Our software suite allows us to view 3D data in novel and unusual ways, to combine and stack filtered images, and to annotate them.

Reporting

The aim is to produce a series of images that will be useful to your project. Where possible this will include an overall image of your rock art panel showing all details as clearly as possible. All projects are documented with what methods were tried; what worked and what didn’t. We will always produce neutral images ready for your team to interpret. However, we may offer some interpretation if required.

A detailed report will examine and illustrate surface features, including those that can be easily seen (and been the cause for a project or survey) along with less obvious details that cannot easily be seen with the human eye alone (at least, until they have been identified).

We tend to ‘journal’ as we analyse rock art, taking screenshots, renders and making notes as we complete an investigation. If you prefer, outputs can be these informal notes and sketches, which show the journey taken to arrive at the finished interpretation.

Techniques and examples

Hendraburnick Quoit

We were commissioned by Cornwall Archaeological Unit to record and digitally enhance the rock art discovered on Hendraburnick Quoit (propped stone) on Bodmin Moor, Cornwall. Our investigation more than doubled the number of known features on the stone. We located 105 cup marks and 47 possible grooved lines connected or radiating from them, following the slope of the stone.

Our research was covered in The Telegraph who used the curioisty-grabbing headline “Ancient stone monuments may have been used for mysterious moonlit ceremonies, say archaeologists“. A full account of the project and our interpretation of the site can be found in the article Hendraburnick ‘Quoit’: recording and dating rock art in the west of Britain in Time & Mind – the “Journal of Archaeology, Consciousness and Culture”.

Composite image showing examples of digital filtering methods used to enhance the rock art at Hendraburnick Quoit, Cornwall.
Digital rock art enhancement at Hendraburnick Quoit, Bodmin Moor, Cornwall. Multiple techniques were used to create a composite image for interpretation and illustration.

Rock art at Boscawen-Ûn Stone Circle

Plate 77 from Péquart & Le Rouzic 1927, showing the twin feet motif on stone 8 at Dolmen du Petit-Mont.

As part of our technique development we investigated the pair of ‘axe’ carvings at a local stone circle close to Penzance, Cornwall. First noticed in 1986 and interpreted as a pair of axes, we recorded them using SfM photogrammetry. We filtered the data using a number of different approaches (including grayscale and colour depth shading, ambient occlusion, Cook-Torrance shading) to produce the clearest possible images of the carvings.

Our interpretation suggests that they represent a pair of feet, sole outwards. We followed up with some research in the library of the Society of Antiquaries and came across a similar carving (destroyed in the 1940s) at Dolmen du Petit-Mont at Arzon in Brittany.

Composite image showing examples of digital filtering methods used to enhance the rock art at Boscawen Ûn stone circle, Cornwall.
We investigated the ‘axe’ rock art on the central stone at Boscawen Ûn stone circle. Digital enhancement of the panel revealed details which suggest that the carving is a pair of feet, soles facing outwards. This image shows a range of the filtering techniques used to arrive at this interpretation. Examples of pairs of feet similar to this can be found in Brittany.

Our work on the rock art at Boscawen-Ûn was featured on the Prehistory Guys channel on YouTube.

Stonehenge

Tom’s first experience recording and digitally enhancing rock art began at Stonehenge in 2002 long before the establishment of the Curatorial Research Centre. Working as part of a team from Wessex Archaeology and Archaeoptics they aimed to record the known carvings and see how well the then-emerging technology of 3D laser scanning could capture the fine details of these shallow impressions of axes and a dagger on stone 53.

Alistair Carty from Archaeoptics and Tom Goskar, then at Wessex Archaeology, experimented with novel ways of visualising the 3D surfaces. In 2003 the team published the discovery of ‘new’ carvings, previously unrecorded right next to the a group of well-known ones.

The images below were produced in 2021 from the original data captured in 2002. Archaeoptics are acknowledged as the owners of the data.

Early medieval inscriptions and carvings

Most of the techniques used to digitally enhance carved rock art can be applied to decorated stones and inscriptions of any date.

The “Gulval Evangelists” were discovered by Tom Goskar in 2012 using photogrammetry after a series of unsuccessful attempts to use physical raked lighting to identify the carvings. Local stories suggested that they were coats of arms.

Contact

Please email info@curatorialresearch.com to get in touch to discuss your project. We work with clients across the UK and are open to enquiries about international projects.