From Availability to Quality: Diagnosing Encounterability and Perceptual Affordance of the Built Environment in Xi’an’s Old City

Abstract

As urban development in China shifts toward improving existing areas, the focus of evaluation is moving from availability to quality, yet assessments of the neighborhood built environment and living circles still stop at facility provision. This study decomposes the conversion from spatial supply to need fulfillment into three links—availability, reach-and-visibility, and need fulfillment. Encounterability (E) captures how far a spatial element enters everyday experience through physical reach or visual exposure; perceptual affordance (P) captures how well an encountered element supports six perceptual needs: social interaction, recreation and leisure, aesthetic experience, emotional experience, broad learning, and humanistic enrichment. Taking Xi’an’s historic old city as a typical case, public needs were translated through grounded coding into auditable elements, which trained assessors evaluated at the city, district, and neighborhood levels, with a four-quadrant diagnosis locating the gaps. The results show that, within this context of comparatively rich provision, the principal experiential gaps arise at the encounter and support links: encounterability is similar across levels while perceptual affordance diverges, and the share of synergy categories differs significantly across levels (p = 0.007), forming resource–encounter, node–route, and frequency–support mismatches; the principal mismatch patterns are robust to equal weighting and to moderate shifts in the quadrant thresholds. Basic needs fail on quality and advanced needs fail on encounter and interpretation, pointing to three renewal actions: retrofitting, opening, and interpretation. This study extends evaluation objects from facilities to a fuller spectrum of spatial elements, extends encounter to reach and visibility together, and extends output from ranking to gap localization, offering a low-cost diagnostic tool for the human-centered assessment of the built environment, applicable to living-circle evaluation, urban physical examination, and livability improvement in historic neighborhoods.