An integrated deep learning approach for assessing the visual qualities of built environments utilizing street view images

Investigating residents' visual preferences and perception of built environments is crucial in visual landscape assessment (VLA). While traditional methods face challenges in large-scale applications, the advancement of deep learning techniques and the availability of street view images (SVIs) present new opportunities. However, existing approaches for assessing SVIs' visual qualities are of lower precision, and the link between objective visual elements and subjective perceptions of SVIs remains unclear. In this study, we propose a novel deep learning approach, "SegFormer-B5 + ConvNeXt-B + RF", which achieves an average accuracy of 78.47% in predicting six subjective perceptions (beautiful, boring, depressing, lively, safe, and wealthy) within the Place Pulse 2.0 dataset. This provides an effective tool for assessing citizens' visual perceptions of urban environments. Subsequently, to demonstrate its practical application, we conducted a case study using 36,620 SVIs from the Tianhe District of Guangzhou. Perception maps were constructed based on four objective metrics and six subjective metrics. Results showed a correlation between the spatial distribution of objective visual elements and subjective perceptions, with city centers generally perceived more positively than suburbs. Our application of SHapley Additive exPlanation (SHAP) and Class Activation Map (CAM) visualizations yielded interpretable insights consistent with eye-tracking studies, highlighting human focus on artificial objects, attractive and unattractive elements, and heterogeneous landscapes. It's noteworthy that urban planners and decision-makers in other cities can apply our approach to generate perception maps that identify low-quality areas. SHAP and CAM visualizations further assist in understanding which aspects draw human attention in these areas. This knowledge is crucial for urban designers to implement targeted renewal strategies, ultimately contributing to the creation of sustainable and living-friendly cities.