Matt Ritchie
The spectacular Neolithic rock art at Ballochmyle extends over three vertical panels on a cliff face overlooking a tributary stream of the River Ayr. The cup-and-ring marks were recorded by RCAHMS in 1986 as a series of detailed pencil drawings and by AOC Archaeology using a combination of terrestrial laser scanning and photogrammetry (Stevenson 1993; AOC Archaeology Group 2015).
The resulting visualizations capture the carvings in exceptional detail. The survey was undertaken to inform conservation management and to contribute to the development of the survey and visualization methodology of prehistoric rock art. The resulting datasets were processed into high-resolution geometric meshes for visualization under simulated raking light conditions. They were prepared for processing in GIS, allowing visualization techniques more usually applied to the interpretation of terrain and surface models generated by aerial laser scanning.
Visualising the geometric meshes under simulated raking light allows the accentuation of shallow carvings under lighting conditions that could never be replicated in the field through photography, with the added advantage of being able to remove the real colour from the rock face (meaning that colour and contrast variations do not distract from the observer’s reading of the carvings).
Analytical hill-shading, slope and local-relief techniques were also used to interrogate and present the geometric meshes. Analytical shading techniques such as these can identify very slight undulations in the rock surface and can provide a complementary source of information to traditional drawn interpretation. They can also provide evidence of more carvings than can easily be detected with the naked eye. Like the simulated raking light applied to non-textured geometric meshes, analytical shading removes the distraction of colour and contrast, relying on differentiation in relief alone to distinguish incised markings.
Forestry Commission Scotland (FCS) commissioned the integrated (or mixed mode) archaeological measured survey at Ballochmyle to help further develop the survey and visualization methodology of prehistoric rock art using a particularly significant and fragile site. This site-specific approach to archaeological measured survey lends itself to clear and concise reporting with an emphasis on creative archaeological visualization. The layout of the resulting has been specifically designed to accentuate the visual elements of the survey—and the ethos of creative archaeological visualization is evident throughout, most obviously in the experimental combination of geometric mesh overlain by pencil drawing.
Figure 1: The Neolithic rock art at Ballochmyle extends over three vertical panels on a cliff face overlooking a tributary stream of the River Ayr. © Forestry Commission Scotland by AOC Archaeology
Figure 2: The detailed and comprehensive pencil drawing prepared by the RCAHMS (Ian G Scott and John Stevenson 1986). Crown Copyright: Historic Environment Scotland
Figure 3: This oblique visualization of the third panel (which measures about 9 m in length) shows the high resolution geometric mesh (created using both laser scanning and photogrammetry) overlain with the RCAHMS pencil drawing. The technique provides enhanced visual depth to the traditional illustration. Copyright: Forestry Commission Scotland by AOC Archaeology and Historic Environment Scotland
Figure 4: This rectified high resolution geometric mesh of the third panel at Ballochmyle presents the objective record visualised with simulated raking light. Copyright: Forestry Commission Scotland by AOC Archaeology Group
Figure 5: This local relief model of the third panel uses a red-white colour ramp (above), with the same data presented with the colour ramp inverted (below). Copyright: Forestry Commission Scotland by AOC Archaeology
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