[CAA 2015 – session 3C abstract]
The communication deals with a method for graphical recording of planar engraved surfaces with wide extension able to maintain a high degree of accuracy and resolution. This method uses digital photography and a dedicated software and produce the map directly in a digital image format…
by Paolo Emilio BAGNOLI, Andrea SAMUELI
43rd International Conference on Computer Applications
and Quantitative Methods in Archaeology (CAA 2015)
Session 3C: Computer and rock art studies:
data collection, interpretation and communication
[March 31 2015, Siena] – abstract
Computer graphics-aided recording
of open-air extensive rock-art panels
The accuracy (minimization of measurement errors) and resolution (minimum size of details) of the graphical documentation of archaeological sites or objects, including rock-art, is an essential requirement for the correct interpretation and conservation.
In the case of recording of widely extensive rock-art panels using conventional techniques, the preservation of the two above properties may imply a dramatic increase of the execution time, both in situ and in the post-processing phase. On the other hand in some cases the time and/or environmental conditions (urgent archaeological digs, underwater digs, rock art placed in dangerous or elevated positions) make the use of sophisticated scanning equipment unsuitable and should require faster, low-cost but still accurate recording methods, at least in the acquisition phase.
The present communication deals with a method for graphical recording of planar engraved surfaces with wide extension able to maintain a high degree of accuracy and resolution. This method uses digital photography and a dedicated software and produce the map directly in a digital image format.
Beside it was firstly designed and applied to record rock-art sites in the Apuane Alps (Tuscany, Italy), however it may be applied to several other archaeological contexts.
The main characteristics of the method are the followings:
- it allows the minimisation of the needed distance measurements and therefore greatly decreases the time to spend in situ;
- it can be applied mainly on planar surfaces, also with wide extensions and/or where the spatial relationships among different groups of details are crucial;
- high degree of accuracy and graphical resolution may be achieved;
- it does not require regular grids but only irregular ones; The application of the whole method consists of three different operative phases on the field and three phases of data post-processing with the help of a dedicated software program.
The three field actions are:
- the built-up of an irregular grids of points (primary and secondary measurement stations) where each point is progressively numbered;
- digital photographs of the details where each photo contain three points (stations);
- measurements of the distances among the primary stations and between each primary station and all the secondary ones.
The post-processing phases are:
- built-up on the computer of the grid map of the stations using the software programs;
- two colour contour tracing of the details (including the position of the stations) on each photo also eliminating the useless substrate;
- pasting in semitransparency the photos on the grid map by connecting the stations on the photo with the corresponding ones on the map.
Finally some application examples performed by the archaeological groups of Pisa and Massarosa will be shown.
At the time of the conference the used software, implemented in MATLAB environment, will be given on the web as open source program.
Paolo Emilio BAGNOLI
Department of Information Engineering, University of Pisa – Italy
Archaeological Group of Massarosa – Italy