Abstract
Abstract. Nowadays, considering the various methodological approaches used by the scientific community to study graffiti, there is a need for the improvement of the documentation and analysis workflow that must be addressed. Historic graffiti are recognized by scholars of different disciplines as a relevant and genuine written source, able to provide an insight into the everyday life of the past. Many studies have indeed flourished during the last decades stating the relevance of graffiti as a multidisciplinary source of information and showing, at the same time, the fragmented research scenario due to the lack of reliable and standardized methodologies. Currently, the scientific community involved in the study of graffiti has largely benefited from the use of digital technologies. However, most of the efforts and research projects were focused on the analysis of graffiti immediately visible on the surface or graffiti the position of which was easily identifiable due to the depth and width of the engraving. The proposed study is intended to tackle the documentation pipeline a step earlier than the documentation itself when the graffiti are yet to be identified. The San Marco Basilica in Venice is used as a unique case study for the analysis of non-directly visible-to-human-eye graffiti in a rather challenging environment.
Highlights
1.1 Traditional Graffiti Documentation MethodologiesThe main issues in reproducing graffiti are represented by the light scratches composing their ductus, which is difficult to recognize or not visible at all using traditional photographic techniques
Image-based modelling coupled with Reflectance Transformation Imaging (RTI), Infrared Photography (IR) and X-Ray Fluorescence (XRF) for the study of two mural paintings and their historical graffiti located in the catacombs of San Giovanni in Syracuse (Italy) were used by (Cosentino et al, 2015)
After a photogrammetric survey of the marble decoration and the production of the relative orthophotos where graffiti are suspected to exist, the pipeline consists of (i) computation of edge-detection to identify graffiti; (ii) computation of change-detection to highlight the differences between the pre-processed image and the one created by the edge-detection algorithm
Summary
The main issues in reproducing graffiti are represented by the light scratches composing their ductus, which is difficult to recognize or not visible at all using traditional photographic techniques. Graffiti have been mostly documented through handmade copy This method is easy to apply since it uses a transparent sheet, a marker and a flashlight. Often the help of a flashlight is required to better identify the scratches This is the simplest documentation workflow, but scholars are aware of its limitations. Criticisms about the mechanical copy concern: (i) the spatial distribution of graffiti in a large area, documented only through the use of transparent, can be lost, together with the mutual relations between them; (ii) the handmade material copy requires direct contact between the transparent and the surface, a factor that sometimes may affect the support conservation conditions; (iii) at a later stage, the copy made on transparent is challenging to be implemented and transferred into other systems, both printed and digital. Criticisms about the mechanical copy concern: (i) the spatial distribution of graffiti in a large area, documented only through the use of transparent, can be lost, together with the mutual relations between them; (ii) the handmade material copy requires direct contact between the transparent and the surface, a factor that sometimes may affect the support conservation conditions; (iii) at a later stage, the copy made on transparent is challenging to be implemented and transferred into other systems, both printed and digital. (Horn et al, 2018)
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