Graffiti is a short-lived form of heritage balancing between tangible and intangible, offensive and pleasant. Graffiti makes people laugh, wonder, angry, think. These conflicting traits are all present along Vienna's Donaukanal (Eng. Danube Canal), a recreational hotspot in the heart of the city which is famous for its seemingly endless display of graffiti.

The two-year INDIGO project aims to build the basis to systematically document and monitor 6.6 km of Donaukanal graffiti in the next decade. The first aim is to photograph all present and new graffiti in a colour-accurate way. The engagement of artists will ensure that many sprayings get documented soon after their creation. Visits every couple of days and a bi-annual total photographic coverage should pick up most of the remaining graffiti. All images get processed into detailed, distortion-free orthophotographs and textures for the 3D surface model of the canal banks (provided by the City of Vienna). The OpenAtlas spatial database manages all these data, along with auxiliary data (like videos) and relevant metadata such as style, artist, legal status, and lifespan.

Finally, an open-access online platform enables the interactive 3D visualisation and exploration of this database: sliders to display graffiti through time or spatio-temporal queries like "all political messages from 2021". Since storage in the ARCHE repository ensures the necessary digital longevity and free download of all data, INDIGO can realistically preserve and disseminate the thoughts and artistic expressions of society sprayed upon its walls.