ETH Library has an extensive and historically valuable collection of more than three million photographs, postcards, aerial pictures and portraits in its Image Archive. More than 500,000 photographs and images have been digitised and can be searched for on the platform e-pics Image Archive Online (ETH Zurich, 2019).

The Image Archive was the first unit to start a crowdsourcing campaign. After Swissair, the Swiss national airline, went bankrupt in 2001, ETH Library happened to acquire the Swissair Photo Archives. In 2009, former employees of Swissair were invited to improve metadata. They were given the chance to share their knowledge on around 45,000 images in an easy way, which this determined group of experts accepted enthusiastically (Graf, 2016). In this project, the volunteers took part at level one and partly also at level two of Haklay’s typology, i.e. citizen scientists participated as sensors and performed basic interpretations (2013, p. 116).

The Image Archive was a pioneer in terms of implementing an open data policy, too. At the beginning of 2015, it changed its business model. Instead of trying to sell high-resolution images, which had not turned out to be profitable, it started to offer its photographs for free download, even in the highest resolution available and for commercial use whenever there were no third-party rights. As a result, resources used to fulfil orders, issue invoices and monitor accounts were freed for more forward-looking activities (Graf, 2015).

Given the outcome of the Swissair project, the Image Archive opened its database for general user comments regarding all images in December 2015. On January 18, 2016, Neue Zürcher Zeitung, a leading Swiss newspaper, published an article before the marketing campaign had even started (Kälin, 2016). This triggered a breakthrough, which resulted in a report being broadcast on Swiss television’s main news programme the very same evening and elicited an extensive media response in the days and weeks that followed (Graf, 2017). In the wake of this unexpected promotion by the media, the Image Archive started the blog Crowdsourcing: News and Experiences from the Community (ETH Library, 2019b). Since May 2016, it has published quizzes and appeals inviting readers to get involved. The crowd was asked to help describe images on Mondays, and the feedback received was documented on Fridays. Rankings and community events stimulated crowd participation. All in all, 1,109 volunteers had improved the metadata on 68,488 images with 70,555 hints by December 1, 2019. The distribution of work among the volunteers confirms earlier findings from all over the world: a small minority did the majority of the work (Holley, 2010). One reason for the affirmative response is the fact that the volunteers were able to download their preferred images in high resolution and re-use them thanks to ETH Library’s open data policy, and the feedback function’s user-friendly design. While no systematic collaboration with the media existed, such as that in Denmark (Overgaard & Kaarsted, 2018), the Swiss media crucially supported the Image Archive’s efforts by taking up the topic and encouraging citizens to participate in the project.

In 2018, the Image Archive launched a campaign on sMapshot, “the participative time machine”. sMapshot is a platform for interested participants to position and geolocalise historical images on a virtual globe. The virtual globe is based on the latest satellite images and Swisstopo’s 3D buildings. sMapshot is a project conducted by the Laboratoire de SIG, Haute École d’Ingénierie et de Gestion du Canton de Vaud (HEIG-VD). It allows the camera position, line of vision and height from which the photograph was taken, all the place names visible in the picture (places, rivers, fields, mountains etc.) and so-called footprints to be calculated (Graf, 2019). This tool has “become highly addictive”, as the head of the Image Archive predicted at the launch (Graf, 2018). Promoting competition by publishing statistics (Figure 1) and adopting a gamification approach proved to be effective: 189 participants have georeferenced nearly 100 percent of the 68,430 aerial photographs published since January 2018 (HEIG-VD, 2019).

Why does it work? Apart from open data and gamification, community management is the key to success. Social media and the above-mentioned blog allow ETH Library’s staff to interact intensively with the crowd. This is, however, not enough. The volunteers are invited to ETH Zurich at least once a year and receive awards in public for their contributions to our catalogues (ETH Library, 2019c). Six of them were thanked by publishing video interviews (Figure 2) in which they explain (in German) why they participate in our campaigns (ETH Library, 2019d). The videos are available on YouTube and accessible for the long term on ETH Zurich’s video portal.

Given the positive outcome of crowdsourcing at the Image Archive the opportunity to comment on images was implemented in the Collection of Astronomical Instruments, the Art Inventory and most other E-Pics catalogues. E-Pics is ETH Zurich’s platform for images, photographs and illustrations (Foulger & Wiederkehr, 2018).

ETH Library’s Map Collection also adopted a crowdsourcing strategy in order to georeference old maps for further academic use and integration in geoinformation systems (Walt, 2019). 1,135 historical maps were processed within a few months in 2017, when the Map Collection made them available on the platforms www.oldmapsonline.com and www.georeferencer.com and addressed the crowd via social media channels (Walt, 2017). The Map Collection’s next campaign is scheduled in the autumn 2019.

e-manuscripta.ch, the co-operative digital platform for manuscript material from Swiss libraries and archives technically hosted by ETH Library, has offered a transcription tool for the crowd since 2018 (Renggli, 2018). Until recently, only image scans of archival documents were published. The crowd has not been as active in transcribing documents and thereby creating full text as in improving metadata of photographs. The reasons may be the following:

As a result, ETH Library is planning a transcribathon in order to meet the potential crowd at ETH Zurich and foster friendly competition. The ETH University Archives also invite professors of history to teach courses based on materials published in e-manuscripta.ch. The idea is that the students have to transcribe sources before they analyse them. These efforts are still to come in order to transfer the positive experience with crowdsourcing of visual material to textual documents.