why | how

5 pillars

As mentioned in the previous section, INDIGO wants to build the basis to systematically document, disseminate and analyse almost 13 km of uninterrupted graffiti along Vienna’s Donaukanal (Eng. Danube Canal) in the next decade.

In doing so, INDIGO wants to digitally preserve this unique, complex, short-lived and socially relevant form of cultural heritage, as such leveraging its potential to disclose new socio-political-cultural research questions and graffiti-specific insights.

To accomplish those aims, INDIGO is structured around 5 research pillars of which the goals, challenges and expected results are detailed below.

To provide clean and relevant data for the spatial database and online platform,

  1. three-dimensional (3D) surface geometry of the Donaukanal,
  2. photographs of the graffiti, and
  3. auxiliary data must be acquired.

The 3D surface is vital to remove the geometrical image deformations (see B); it is also the backbone of the online platform (see D) onto which the graffiti images are mapped. The challenge lies in the acquisition of accurate and complete 3D geometry of the canal’s banks.

Although INDIGO can use the detailed 3D point clouds collected through Vienna’s Wien gibt Raum initiative (Eysn, 2020), some extra laser scanning and image-based modelling might be needed to avoid data gaps. The real challenges, however, relate to the photographic image acquisition.

Photographs should be colour-accurate and obtained as soon as possible after the finalisation of the graffiti. INDIGO solves the last issue through (personal) contact with many graffitists and Donaukanal visits on a two- to three-day basis (for which three photographers are available). A bi-annual photography campaign of the whole 6.6 km will allow change detection algorithms to pick up graffiti that went unnoticed.

However, reliable change detection, smooth transitions between overlapping images, and graffiti pigment identification all need colour-accurate photographs. Even if hard to achieve outdoors (Verhoeven, 2016), we expect to do better than anyone has accomplished so far.

Finally, relevant auxiliary data must be collected: graffiti metadata (like creation date, artist, graffiti type) or the videos and pictures that artists record during spraying. The challenge here lies in getting all the necessary metadata for every piece of graffiti. Many creators prefer anonymity, which is why the online platform will feature anonymous login for metadata entry.

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.

methods and tools

work plan

INDIGO is a two-year project which started the 1st of September 2021. INDIGO is thus spread over eight project quarters, with Q8 ending on the 31st of August 2023. Some activities like website and logo creation commended before the project start. They all fell within Q0 (see Gantt diagram).

Managing time and resources in INDIGO is supported by the project management tool Teamwork.

Workpackage no.

Short description



Management: daily project management, kick-off, and other meetings

Q1 to Q8


Awareness: creation of logo, social media, flyers, QR-stickers, leaflets, and basic website + SprayCity workshops

Q0 to Q8


Hard- and software acquisition: research and buy all necessary consumables to purchase



Legislation: sort out copyright and aspects of legal data sharing



Photography: daily and bi-annual graffiti recording

Q1 to Q8


GNSS/IMU: implementation + optimisation of camera coupling with GNSS/IMU devices

Q1 to Q3


3D geometric backbone: add-on photography and scanning to complement Stadt Wien’s point cloud + meshing + mesh segmentation

Q1 to Q2


Colourimetry: research and develop a workflow and tool for colour data acquisition + processing

Q1 to Q4


Orthorectification and texturing: research and develop a workflow and tool for photograph orthorectification and mesh texturing

Q1 to Q4


Segmentation and annotation: research and develop a workflow and tool for image segmentation and annotation

Q1 to Q4


Change detection: research and develop a workflow and tool for image change detection

Q3 to Q4


Image processing: colour correct, orthorectify, segment and annotate photographs with the tools and guidelines developed

Q5 to Q8


Thesaurus: research and develop a graffiti thesaurus and get community feedback

Q1 to Q2


Spatial database: research and develop the conceptual and logical data model with standardised metadata and get community feedback; implement the physical model in OpenAtlas.

Q1 to Q4


Data ingestion: link ARCHE with OpenAtlas and ingest all raw and processed data; also ingest images to SprayCity

Q1 to Q8


Online platform: research, wireframe, and develop a 2D platform with links to ARCHE and OpenAtlas. Research the 3D visualisation part and add it to the 2D platform

Q2 to Q8


Symposium 1: organising + contributions + proceedings

Q2 to Q3


Symposium 2: organising + contributions + proceedings; this WP also covers the database analyses (to be presented at this symposium)

Q6 to Q8


Fundraising: Stadt Wien + new project proposal