3D Laser Scanning at Church Hole, Creswell Crags

Abstract

The process of recording in situ archaeological art can be a time-consuming and complex task, especially on inaccessible and non-planar surfaces such as those found in Church Hole, Creswell Crags. There are considerable challenges to the recorder, including the accurate positioning and fixing of survey frames, the physical discomfort of sitting, crouching, or even lying down for long periods of time in cramped surroundings, and, ultimately, the difficulty in interpreting the panels to enable accurate recording. Furthermore, the more accurate forms of traditional recording include the taking of rubbings of the carvings, a process known to increase the potential of damage to already fragile artworks. 3D laser scanning offers solutions to most of these problems by quickly producing a highly dense fully three-dimensional surface map of the art which can be studied in more conducive circumstances by researchers at a later date. Furthermore, powerful visualization techniques can be applied to the 3D surface map to extract and enhance detail that might be virtually invisible to the naked eye. Over-arching the visualization and interpretational aspects of 3D laser scanning is the potential to use the acquired 3D surface map to monitor any change in the surface through repeated scanning over a period of time. This technique is suitable for detecting minute differences in the surface over time, including both erosion due to natural processes or vandalism and accretion through build-up of deposits on the surface of the art. The most complex aspect of three-dimensional recording, no matter what the subject matter, is that of the third dimension. People have an almost schizophrenic way of looking at the world. For example, if you were to place two identical objects a distance apart, it is simple to state that one object is further away than the other due to our perception of depth and the ability to walk around the two objects. However, if you were to take a photograph or make a drawing of the scene from one point of view, it becomes difficult to tell whether two identical objects are placed some distance apart, or if two differently sized objects sit beside one another. The three-dimensionality of the scene is now lost and is available by inference only.