why | how

All three datasets must go through one or more processing steps before being inventoried in the spatial database. As a start, all datasets receive the necessary metadata (e.g. IPTC tags for the imagery). The photographs will go through a strict routine to create 16-bit colour-accurate TIFFs (Molada-Tebar et al., 2019). The challenge here is to create a robust and repeatable workflow that maximises throughput.

Afterwards, an orthorectification process removes the geometric distortion of the images (Kraus, 2007). To that end, the 3D point cloud is meshed into a continuous surface, after which the tricky task awaits of segmenting and labelling the mesh into logical units (e.g. distinct physical structures like a bridge pillar or an underground construction element).

INDIGO needs a bespoke tool that can load just the necessary mesh segments to create orthophotographs and mesh textures. Ideally, this tool can also process the photographs that reside in the SprayCity archive. The bespoke software should also support the change detection operation required by the bi-annual photographic campaign described in pillar A, making its development challenging.

Finally, finding and documenting new graffiti is useless if the resulting data are not searchable. Therefore, INDIGO expects this tool to support image segmentation and annotation (e.g. new graffiti, old graffiti, no graffiti zones) and – through a spatial database link – the attribution of metadata.

Collecting and processing data without a sound data management system is irresponsible. This pillar aims to create a conceptual data model and implement it in a spatial database to manage and query all (meta)data. The need for a specific ontology, robust database integration with the online platform (see D), support for spatio-temporal queries, and adherence to the CIDOC CRM ontology standard make this task considerably challenging. At the same time, data entry should be customisable and painless.

Due to the existing Vienna-based OpenAtlas software (OpenAtlas team, 2020) and targeted programming, INDIGO expects its database and underlying data model to be an example for the Digital Humanities at large.

To tackle long-term digital preservation challenges, INDIGO will store all data in the certified ARCHE repository (Trognitz and Ďurčo, 2018).

An open access online platform ensures interactive visualisation and exploration of the data. Textured 3D views allow visitors to look at present-day graffiti in their geographically-correct urban setting or scroll through time and visually experience the works’ time-span.

A section to browse through detailed graffiti orthophotographs plus functions to download and extensively query (meta)data is also present. Although creating such a platform with slick user experience is a challenge (e.g. a pleasing layout, smooth data streaming, robust database integration), in a post-project future it could lead to an augmented reality app.

Even though articles and conference talks accomplish international outreach, they do not instigate the graffitists’ essential engagement. The latter is achieved via regular graffiti workshops and leaflet distribution by SprayCity. Combined with the QR-encoded stickers along the Donaukanal, these initiatives create the necessary local awareness to extend the foundations laid by INDIGO into the next decade (e.g. via citizen science).

Moreover, INDIGO plans two international symposia. The first one will take place six months into the project and tackle the technical aspects of recording, storing, and disseminating graffiti. Gathering experts so early on helps to avoid pitfalls further down the road.

A second symposium on graffiti’s socio-political and cultural impact is planned for the end of the project. This gathering marks the online platform’s launch and showcases how its stored graffiti (meta)data enables societal and cultural insights.

In this way, specialists in art history, philosophy, cultural studies, law, urbanism, psychology, and communication will see the potential of this massive open access archive, thereby ensuring this project’s transdisciplinary sustainability. Both symposia proceedings – planned to be published at their respective starts – might also become foundational publications on graffiti research.

Most of the scholarly literature on graffiti is exclusively descriptive, often devoid of essential metadata (e.g. Reinecke, 2012; Wacławek, 2011). This lead some scholars to blame graffiti research for its overall lack of academic rigour (de la Iglesia, 2015).

Given the exhaustive and spatially + temporally + spectrally impartial inventory of graffiti (meta)data, INDIGO’s open access archive will open new analytical pathways for graffiti research that support novel socio-political-cultural research questions. For instance, Vienna counts several legal spraying surfaces, collectively labelled as the Wienerwand.

Along the Donaukanal, there are approximately 300 m of Wienerwand. One may wonder if those who spray in legal graffiti zones have the same profile as those who do not, and if ‘artistic value’ and ‘legality’ are connected.

These walls could also offer insight into ‘dissing’, a phenomenon where graffiti – usually tags – are scrawled over a major (often solicited) graffito (McDonald, 2013).

Analyses like this also directly tie into existing graffiti definitions and classifications. Some scholars and graffiti artists voice that legally permitted graffiti do not deserve the label ‘graffiti’ (Tomàs et al., 2014). Even though such terminological distinctions do not guide INDIGO’s recording, the project must strive for terminological clarity to populate the database with unambiguous metadata.

The creation of a graffiti and street art thesaurus in the first project months will accomplish this. Being a finite set of terms (i.e. a controlled vocabulary) with hierarchical relations (Pomerantz, 2015), this thesaurus will make INDIGO’s graffiti/street art classification explicit and serve as a reference for the broader academic graffiti community.