Construction of urban collective memory maps based on social media data: a case study of Nanjing, China

Rapid urbanization, which often overlooks the socio-cultural attributes and values embedded in urban space, has intensified problems of “placelessness” and a weakened sense of public identity. Examining city–public interactions through the concept of urban collective memory helps forge an operational, quantifiable link among the built environment, social identity, and historical continuity. Using Nanjing as a case study, this research integrates collective-memory theory with the urban-image framework. Drawing on geotagged “digital network memory” data from social media, we apply natural-language processing (NLP) and geographic information system (GIS) techniques to aggregate individuals’ spatial images and construct an urban collective-memory map comprising paths, nodes, landmarks, districts, and edges. The findings show that collective memory can be both spatially visualized and quantified, while revealing clear regional differentiation. Consequently, the study provides a sociologically grounded method for assessing urban spatial value that informs evaluations of urban resilience and cultural continuity.