Employing our PTM data, we report on four outstanding aspects of the Avencal 1 engravings which the technique has been instrumental in discovering. In section 3.1, we briefly compare the PTM record with the publication of the site by Rohr (1971). Secondly, we present a novel usage of the technique: prospection for imperceptible or near-imperceptible features on 'blank' rock faces. A similar approach was adopted by English Heritage researchers at the site of Stonehenge (Abbott et al. 2012) and applied to virtual data, as opposed to the example presented here, which uses 'field data'. Thirdly, we show an example of superimpositioning within motifs, permitting insights into the sequence of creation of a common type of geometric engraving. Finally, we present a detail of Panel 1A (Figure 13), which exemplifies the various techniques employed by the creators of Avencal 1 to produce the record as it appears today.
Figures 5 and 6 directly compare the record by Rohr (1971) with the data captured during PTM fieldwork. The original plans of the site, which have served as points of reference for all subsequent studies of the site, are widely reproduced as black-and-white line drawings. Translating three-dimensional surfaces into flattened representations is a subjective process, owing to the technological limitations of drawing and sketching (Coles 2003, 567; Simpson et al. 2004).
These panels exemplify these issues, as evident from direct comparison between plans and their corresponding PTM (Figure 5 and Figure 6). This highlights the difficulties in creating an objective record of the site through line-drawn interpretations of the engravings, an issue whose potential negative effects can significantly skew later research. The first bears a schematic representation of an anthropomorph and several geometric engravings. It is recessed by several millimetres as a result of visible preparation of most of the engraved surface by pecking. Owing to this, the line connecting the head and shoulders is interpreted as part of the engravings, while PTM reveals it to be a by-product of the surface preparation. Several small features that are easily visible within the top-right geometric engraving of the PTM would have been problematic to pick up through the semi-translucent tracing paper. Finally, the convexity of the rock face resulted in the orientations and relative sizes of each motif within the plan being inconsistent with the panel. Figure 7 displays the normals of Panel 3A, indicating the curvature of the engraved surface. This could have complicated a faithful reproduction of the motifs.
The second example also possesses several omissions in the plan that the PTM was successful in detecting. It is now possible to view how certain motifs within the panel, especially towards the bottom and right of the image, are distributed relative to each other at the correct sizes and orientations. In terms of level of detail and accuracy, these examples are representative of results from within Avencal 1 as a whole. Our findings suggest that scale is well preserved in the plans made by Rohr, owing to the tracing being taken at 1:1 scale. The topology and level of detail are, however, far superior in the PTM dataset.
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