Since rock art has begun to be recorded, centuries ago, the purpose of such records has always been to create a visual register of those aspects of the art that were deemed important. This has remained so until quite recently, and it follows that rock art recordings are usually interpretations of individual observers, not objective data. Indeed, this principle is embodied in a ruling of the High Court of Austria in 2003, that rock art recordings are copyrighted because they are individual interpretations by the recorder. This is now changing with the introduction of sophisticated digital recording systems that yield much more objective results.
Nevertheless, the ready availability of computer equipment and electronic image manipulating software does not necessarily obviate other recording techniques. The discipline has in the past made the mistake of ignoring useful approaches, such as rock surface cartography as initially developed by Franc:ois Soleilhavoup. It would be precipitate, therefore, to jettison all earlier methods, but it is certainly appropriate to discard all those that are invasive or threaten the research integrity of rock art. Many of the latter have been used extensively in the past, but there is absolutely no justification now to continue with any of them. These physical enhancement methods have included the application of clear liquids to close the pores of silica skins or other thin accretions, thus improving photographic records. The liquids used in this have ranged from water to motor oil, from kerosene to clear lacquer. Another common practice has been the outlining of rock art with chalk and a variety of other markers, including dye, pencil, lipstick, and felt pen. Archaeologists have contaminated the geochemical fabric of thousands of square meters of petroglyphs by applying organic white and black paints, to facilitate manual recording. The use of pressure-sensitive films, rubbings made with a great variety of materials, the production of casts from latex, plaster of Paris, papier mache, thermoplastic resin, and so forth have all been found to affect the rock art, and in some cases have caused spectacular damage to it. The use of transparent film to copy the art can also be damaging, because these sheets tend to be electrostatic and the movement of pens or fingers can attract small flakes of material from paintings. Even the use of aluminum foil tamped gently into petroglyphs before it is backed by stiffer material, regarded as a reasonably safe method, has at last been opposed by a chemist working with rock art (Figure 3).
There is one very simple rule now in recording: unless the rock art in question is about to be destroyed by other factors, no invasive method, no
Figure 3 Damage caused to petroglyphs by contact recording, Vorobiovo site, Siberia. Photograph by R. G. Bednarik.
Contact is acceptable. The first consideration in all rock art recording work must be that it would be selfish to prejudice any future analytical methods rock art scientists will bring to bear upon the rock art, centuries from now. Since we have not the faintest idea what these future methods will involve, there is only one possible solution: all rock art recording today must be by noninvasive methods, except in circumstances where the rock art is subject to other imminent threats.
There is no need to resort to damaging and superseded methodology. Photography, sometimes in combination with noncontact enhancement techniques, is now universally available. Raking light photography (oblique lighting at night) is far more effective in recording petroglyphs than manual recording, which is a cumbersome and subjective procedure. It can be most conveniently accomplished with battery-powered movie lights. A variety of filters and special films are available to improve photographs of rock art. Cross-polarized photography, using two light sources with polarizing filters, can greatly enhance contrast. It is important that a calibrated color and gray scale be included on all rock art photographs, the most widely used being the IFRAO Standard Scale. This has a number of purposes, the foremost being the facility of color reconstitution. All photographic records are of distorted color, and all of them fade with time; therefore, a color profile included on a photograph permits the digitized recovery of original color of the object at the time the image was taken.
The equipment now widely available to rock art recorders includes high-resolution digital cameras which, combined with the use of laptop computers in the field, have revolutionized rock art recording. Photographs can now easily be color-corrected on site, as soon as they are taken, right at the panel being recorded. The digital image processing programs now available have replaced the laborious enhancement procedures of the 1980s. In addition to this basic system, several more sophisticated recording options have recently become available. Some remain very expensive but, judging from previous experience, it is only a matter of time before they, in addition, become stock-in-trade, and ever more powerful tools are introduced at the high end. The use of photogram-metry, which has been sporadic in rock art survey work, has experienced a revival due to the introduction of digital elevation model (DEM) software. This can generate accurate three-dimensional recordings of petroglyphs. An alternative approach is the use of laser scanners to produce virtual digital models of great accuracy and versatility. This technique evolved from the need to record the topography of groove shapes, such as those of Scandinavian rune stones. Manual groove topography of petroglyphs, still done in the late 1990s, has now been superseded by automated laser scanning. It yields visualization algorithms that facilitate the use of such recordings in the application of computer-assisted drawing (CAD) programs to rock art, which can create virtual rock art sites. Micro-topography of rock art has also been attempted with a CCD camera by obliquely projecting a grating fine grid (40 lines per mm) over the rock art.
The alternative method of reproducing panels or sites is the production of physical rock art facsimiles. This has been used for many decades, but only sporadically because of the high cost involved. The most celebrated rock art facsimile is Lascaux 2, a partial copy of the famous cave in France. Having been created at the cost of $8 million, it is now viewed by about half a million tourists per year and its cost has been recovered many times over. Facsimiles are constructed by first acquiring the necessary topographic data, traditionally either by photogrammetry or the use of precision theodolites, but more recently by laser equipment. The rock panel is then recreated and the rock art projected onto it. This process is very laborious and involves considerable artistic skills.
World History
