Germany's debate on nuclear energy is characterized by a potential for conflict. With the Repository Site Selection Act, a new strategy was adopted for a participatory search process for the best possible repository site for high-level radioactive waste in Germany. To gain insights into how a Public Participatory GIS application (PPGIS) can contribute to this strategy, a transdisciplinary approach was adopted. By involving a citizen group to take part in the research process, we co-designed and addressed three research questions regarding the role of the PPGIS, its usability and ability to enable dialogue. Key findings include the need for guidance on how to interpret the data provided. Although the potential of a PPGIS to support dialogue is recognized, the need for content moderation emerged as a significant challenge. The transdisciplinary approach was useful in capturing multiple viewpoints and providing new insights into how a PPGIS should be designed to maximize its usefulness.
