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.

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