'Traditional' methods of recording carved stones, including textual description, sketches, metric drawing and photography, have been in place since the end of the 19th century and remain of tremendous value today. (For discussion of drawing of early medieval see Ritchie 1997; 1998; Scott 1997; for comments on Romilly Allen's pioneering use of photography, see 1993a). The advent of digital recording technologies has augmented but not replaced these established methods which retain value, as demonstrated by a comparative study of metric drawing and digital scanning to record prehistoric rock carving at Ballochmyle, which vindicated the analytic value of metric drawing (see Metric drawing: Case Study 31; Ballochmyle: Case Study 24).
Technological and economic constraints on the reproduction of images—which limited the number of images taken and presented, and the use of colour—have to a large extent been overcome by advances in digital printing and dissemination via the web. Black and white photography retains value due to the legibility of monochrome images of carved stone, and should not be set aside despite the ease and affordability of colour photography. Techniques of oblique-flash photography were developed in the 1970s and 1980s by RCAHMS photographers (Figure 11) and by Tom Gray (Scott 1997) and produced striking images and highly legible images of often worn carving (Figure 74). These are relatively low-tech and accessible to non-specialists and for this reason retain value, despite the superior facility of digital visualization methods to vary the position and nature of light sources 'virtually' after capture.
Figure 74: Image of the Craw Stane, Rhynie, by Tom Gray, specially lit to highlight the incised carving of two Pictish Symbols. © RCAHMS (Tom and Sybil Gray Collection)
Archival photographs may have been shaped by artistic/aesthetic considerations (e.g. composition, lack of indication of scale, focus on carved surfaces), commercial potential (e.g. postcards and other material directed at the tourist market), or been driven by the desire to test new technology rather than simply record. Nonetheless they are of considerable value in reconstructing the biographies of stones, of gauging weathering and other damage, and of documenting the changing context of stones, especially their movement around and between sites. To a large extent this is also true of sketches, painting and etchings, if due allowance is made for 'artistic licence'. Maps and plans of diverse types and various scales are an important source of information about the location (and movement) of stones within sites and landscapes, both directly and indirectly via stone-related place-names.
In addition to these non-contact methods, various contact methods of recording were developed or exploited in the 19th century. Conservation practice today would be to avoid potentially damaging contact methods, especially given the availability of non-contact digital techniques. However, these are expensive and require special equipment and technical knowledge. The low-tech alternative of a rubbing made with pencil or wax on paper may have a place in recording when carved surfaces are robust (Figure 75). Paper squeezes were popular in classical epigraphy, especially before the advent of cheap photography, and have occasionally been used in Scotland, despite less conducive weather conditions. Properly stored, paper squeezes are a durable 3D record of stone which would be suitable for digital scanning. Historic (i.e. 19th-century) squeezes might be of use for determining rates of weathering where recent scans are also available. The same applies to plaster casts and other replicas made by creating moulds from the stones, which in Scotland became popular from the second half of the 19th century. The value of these early replications technologies is now being recognised (Foster 2013a; Foster and Curtis 2016). Squeezes and replicas may be the only record we have of the nature, form and materiality of a lost stone. While any contact recording method has conservation implications which mean it is not to be undertaken unnecessarily or without professional guidance, the low-tech/low-cost nature of rubbings and photographs provides opportunities for community engagement and crowd-sourcing of data which are harder to achieve with more specialist recording technologies.
Figure 75: Selection of rubbings of Pictish sculpture made by John Romilly Allen in preparation for ECMS, 1890s. Crown Copyright: Historic Environment Scotland
Digital recording, particularly 3D recording, of carved stones in Scotland has become firmly entrenched in the canon of techniques applied by heritage and archaeology professionals over the last 20 years. This form of record can be seen as sitting on the same continuum as traditional forms of recording, text, sketches, metric drawing and photography, while also raising its own unique opportunities and challenges. Importantly, a key aspect of these technologies are that they are non-contact and allow the creation of accurate three-dimensional records that replace historic contact techniques, such as the generation of plaster cast replicas. The techniques most usually thought of falling under the umbrella of digital recording are technologies that record surfaces in three dimensions and produce records that allow the visualisation and/or analysis of an object in apparent 3D. The techniques most commonly used are laser scanning (see Bryan 2015), photogrammetry (see Lerma et al. 2010), structured and white light scanning, laser line scanning and Reflectance Transformation Imaging (RTI, which while it does not give a true 3D record shares many features with the other techniques: Mudge et al. 2006; 2008) (Figures 76‒78). There is extensive experience in Scotland in the governmental, commercial and higher-education domains of applying these techniques and consequently there is a solid body of knowledge regarding their practical application as well as the selection of the most appropriate 'tool' for the job.
Figure 76: Heritage visualisation students being trained in the use of a Leica C10 laser scanner at Provan Hall, Easterhouse, Glasgow 2016. © GSA, Stuart Jeffrey
Figure 77: Preparing to control the ambient light. This is necessary to undertake photography for Reflectance Transformation Imaging. Lephinkil cup-marked stone near Glendaruel, Argyll and Bute. ©CC-NC-BY the ACCORD project
Figure 78: Using a 'magic pole' telescopic rod to photograph hard-to-reach sections of a WWI memorial. Ensuring complete and overlapping coverage of sites or objects is essential for photogrammetric modelling. Colintraive, Argyll and Bute. ©CC-NC-BY the ACCORD project
The records produced via these techniques can be used to perform the same functions as traditional records, but have a number of advantages and offer the potential of completely new modes of analysis and representation. They generate versatile records which, in theory, are more easily distributed, more easily manipulated and have the capacity to be re-purposed in multiple ways e.g. to study surface condition (Condition monitoring at Ormaig: Case Study 37) or to create replicas. These records have particular utility in recording scripts or carving that lies over multiple or irregular surfaces, the comparison of current interpretations of designs with those in historic records, to distinguish original and later carvings and to distinguish between a stone's natural and carved features. The surface recording resolution possible with some of these techniques also allows the capture of previously unrecordable (e.g. not visible to the naked eye) information and the analysis of surface using, e.g. metric groove analysis (Kitzler Åhfeldt 2013) and virtual lighting (Jones et al. 2015) (Imaging Techniques: Case Study 7). This extreme detail allows the discovery of the processes of the stone's manufacture, including, potentially, the hand of individual artisans as well as subsequent changes in condition through weathering or other processes. Additional benefits of a true 3D digital record include its use as the basis for replication including through '3D printing' (using either additive or subtractive methods), translating the digital into a form of physical replica with multiple uses including teaching, research and display (Robert the Bruce: Case Study 5). This new form of replication raises a number of interesting issues that echo those arising from the growing awareness of the value of historic physical replicas both as analytical tools and important artefacts in their own right. Digital records, through their amenability to multiple forms of manipulation, also allow for the investigation of historic colour, likely original lighting conditions, and the 'virtual' placement of stones in their original landscape setting (Cradle of The Scots: Case Study 19).
There is now an ever increasing body of digital records much of which would support meaningful further analysis, re-use and re-tasking to build on the objective of their original production. This highlights one of the key structural weaknesses that impacts on the reuse of this data. This relates to the management and dissemination of digital records. There is no centralised inventory of 3D records that clearly indicates what has been recorded, how it has been recorded and what formats the data are currently in. This leads inevitably to the potential that work is duplicated, that the opportunity for comparing records generated at different times is lost, as is the potential for thematic studies that draw together records generated from multiple fieldwork events. Underlying this problem are well-recognised issues of long-term data preservation (Richards et al. 2013; Niven et al. 2014), the use of standardised metadata and paradata (see the London Charter; Bentkowska-Kafel et al. 2012; Jeffrey 2010) as well as multiple issues that arise with data sharing under confusing and/or restrictive data licensing regimes. The affordable long-term curation of digital data in all forms remains a thorny issue in multiple commercial, governmental and academic domains, but is particularly acute for high-volume 3D data which often transitions through multiple-file formats, open or proprietary, during the workflow to the final product, raising along the way a chain of, sometimes difficult, decisions for the archivist. As a result very little 3D content finds its way into a Trusted Digital Repository and consequently may be undiscoverable and/or unusable in a relatively short timescale. In addition to the above, there is the broader issue that even where 3D digital datasets are actively curated for future use, they are almost always archived as discrete items, rather than being part of a wider body of information and without mechanisms linking them to broader research material. This situation has arisen at least in part because existing recording strategies are mainly conservation and communications-led, rather than research-driven. Conservation priorities, as opposed to research, tend to be piecemeal rather than thematic and comprehensive. Although, both the ambitious HES Rae project (HS Focus Magazine 2012) and the Scottish Ten project are comprehensive with regard to the legal status of their targets, covering HES properties and Scottish UNESCO World Heritage Sites respectively. Furthermore there remains a sense that current digital recording practice is still being technically led rather than being developed or exploited with the needs of researchers or public audiences in mind. In part, this is because of the difficulty expert recording practitioners and non-technical academics have in communicating at the same technical level. There is both a skills deficit among researchers and an absence of clearly framed research questions, each of which are contributory factors to this communications barrier. Data capture and processing does not tend to include academic support despite a general understanding that it, as with all recording, is at some level a subjective act. Dialogue between technical and academic specialists could enhance the utility of the subsequent datasets. Such co-working could also ensure adequate resolution for research questions and at the same time help refine new research questions. The framing of new research questions is also undermined by the lack of knowledge about what work has been done and what records are available, as discussed above. However, it could also be said that data is not being generated in a cohesive manner because the research community is not saying 'this is what we want to know' clearly enough. The skills gap between academics and technologists may also explain why there has to date been limited research on digital records of carved stones in their reconstructed landscape settings, subject to different seasons, lighting etc. Although the potential of digital recording for individual stones is recognised, we still need to explore more fully the value of what 'virtual re-contextualisation' might deliver.
While there is not yet a seamless integration between the deployment of digital recording technologies and research-led approaches, work with the public and communities of interest through these technologies holds out notable potential as means of engagement (Wemyss Caves: Case Study 36). There is increasing reflection on the nature of the relationships between community groups, digital heritage professionals and the outputs they have created. Such work is indicating that some of the social values invested in the original object can be translated to or recreated in the process of replication and 3D model capture (Jeffrey et al 2015). This is contingent on a number of factors but points to a key aspect of the digital record from this perspective as being the process itself, who does it and why, as much as the actual output files (Community co-production: Case Study 6).
There remains some anxiety over the potential for digital recording to become 'a double-edged sword'. This relates to outmoded 'preservation by record' arguments and the potential that more easily generated accurate physical records (e.g. via 3D printing or other computer-controlled production methods) could be deployed at the expense of conserving physical remains or used to justify rather than simply mitigate the re-location of monuments from their original context and communities. This anxiety most likely arises from some of the grander claims made when the technologies were in their infancy and currently digital recording is considered most useful for analysis, re-visualisation, enhancement or perhaps providing forms of 'remote access' for those not able to physically visit sites. As with all forms of recording, analogue or digital, the final records have multiple uses, but are not considered as surrogates for the original. However, as exemplified by community co-production (Community co-production: Case Study 6) the recording process itself is not a neutral activity and does have implications for how the original is subsequently perceived both by heritage professionals and the multiple forms of community in which the original is situated.