Mapping Collective Memory: A Public Participation GIS Case Study with a Citizen Science Approach

Collective memory—closely related to, yet distinct from, social memory—plays a significant role in guiding the sustainable transition of cities. Multiple qualitative, quantitative, and mixed methods have been employed to investigate collective memory; however, there remains a need to spatially map it for each city to provide decision-makers with a clear, quantitative guide. Such mapping can help preserve and strengthen a city’s collective memory, thereby informing future urban development. This study examines the urban dimension of collective memory—collective urban memory (CUM)—by mapping its tangible, physical aspects through a facilitated Public Participation GIS (PPGIS) approach within a citizen science framework. Due to challenges in encouraging public use of the mobile GIS application QField, we adopted a facilitated PPGIS approach, whereby trained interviewers assisted participants in the data collection process. Results from Oldenburg, Germany, identified several significant urban locations that play key roles in the city’s CUM. Notably, certain places are mentioned disproportionately by different age groups, while a common core set of tangible landmarks emerges across the population. These findings highlight the value of mapping CUM to support culturally sensitive and sustainable city planning.