Prospecting the site and documentation of the petroglyphs - photos of the Toro Muerto Archaeological Project - 2015 season
Everything that has been included in the documentation of the rocks with petroglyphs in the first stage of work (started by the team of the Toro Muerto Archaeological Project managed by Karolina Juszczyk and Abraham Imbertis in 2015-2016, continued and completed by the TMARP in the 2017-2019 seasons) is described in four basic steps, which are:
inventory numbering (starting with TM-0001);
creation of inventory records;
georeferencing of all rocks with petroglyphs.
The labour-intensive and prolonged prospecting of approximately 10 sq km of the site and the recording of almost 2,600 carved rocks (with representations that are visible and beyond doubt, although sometimes very simple) were carried out in small groups of two to three people working in sectors pre-established by the archaeologist and topographer, generating effective and systematic results.
While a member of one team was describing the rocks, another was responsible for the photographic recording of each rock, all of its decorated faces and any possible details. The geodesic specialist provided the points first with the total station (2015-2016) and then with the GPS-RTK, taking three to eight points for each boulder (since 2017).
Location of rock TM-1808 with eight decorated surfaces on the orthophotomap and part of its photographic documentation
The numbering of the inventory was successive and correlated to the progress of the prospecting carried out by the groups in different sectors of the complex and the identification of the following petroglyphs. All the numbers on the rocks introduced by the previous researchers were recorded. However, neither the TMAP (2015-2016) nor the TMARP (since 2017) located their numbers on the surface of the rocks.
The card produced by the project adds up the information related to: the degree of preservation, the number of carved panels (surfaces/decorated faces), type of images, and classification according to the scene, amongst others.
The photographs were taken using semi-professional and professional cameras. All the basic shots show the scale, the north arrow and the colour scale proposed by the International Federation of Rock Art Organisations (IFRAO); in the detailed photos, the scale and colour scale were used. Currently, TMARP has the most extensive digital catalogue of the petroglyphs on the site.
In the most interesting cases, two complementary activities were carried out:
execution of traditional and digital tracings, and
execution of 3D models.
All data recorded in the field has been digitized and, together with information added subsequently (for example, information about the presence of individual petroglyphs in other authors’ publications), is stored in a database available online to all project staff, enabling them to carry out analytical work of various kinds.
Production of classical tracings of rock art – which are justifiably controversial and debatable in the scientific circles in the case of painted depictions (a possibility of damage to the painting) – with regard to petroglyphs does not usually give rise to many objections by researchers. It is considered to be a relatively non-invasive procedure and one of the best forms of documentation of such images. The making of the tracings themselves is useful – it allows for detailed observation of particular motifs, of the ways and techniques of their execution, it also develops a sense of perceiving obliterated or destroyed parts of motifs or compositions more difficult to recognize. In the case of exceptionally well-preserved and visible petroglyphs, you may also choose to document them digitally, using orthophotogrammetry or scanning.
The traditional tracing method uses transparent polyethylene panels that are placed on the surface of the carved rock and allows a motif or scene to be traced with permanent markers of various colors.
The stages covered by this method are as follows:
cleaning the surface of the petroglyph from accumulated dust and sand, using soft brushes;
covering the copied surface with sheets of film;
labeling each fragment of the polyethylene (due to the shape of the rocks and their size, sometimes several sheets have to be put together);
the tracing process itself, in which three different colors of indelible markers are used:
- black (to mark the original petroglyphs);
- blue (to mark everything that belongs to the nature of the rock: grooves, cracks and edges)
- red (to mark man-made destruction or vandalism);
all images copied on the polyethylene panels are then photographed with calibration points to avoid distortion;
finally, based on these photos, the image is processed in graphic programs and vectorized drawings are obtained.