Walking distance to the nearest public green space of at least 1 ha as mapped in OpenStreetMap (3-30-300 rule)
The Distance to OSM Green map measures, for every point of the site, the walking distance along the street network to the nearest public green space mapped in OpenStreetMap (parks, gardens, recreation grounds, accessible woods) with a true surface of at least 1 hectare — the threshold used by WHO/EEA and by the 3-30-300 literature (Konijnendijk 2022; Turner et al. 2025). Areas with private access (access=private/no) are excluded. The pedestrian network is built from OSM roads (3Bee S3 mirror, annual snapshot; Overpass as fallback source), excluding motorways and trunk roads; the per-pixel distance is the leg to the nearest street node plus the shortest path along the network to the green-area entrance (multi-source Dijkstra), with a 1,200 m horizon beyond which the value saturates. The headline KPI is the share of the site surface within a 300 m walk of green: the indicator is weighted on the site area, not on population, so it is not directly comparable with population-based EEA figures. Map classes anchored on the rule: 0-100, 100-200, 200-300, 300-600, >600 m. Auto-scaled resolution (~5-10 m). Unlike the three satellite Green Equity layers (ESA WorldCover), this layer only counts recognised, usable green mapped in OSM and uses network distance, which in urban fabric is 3-13 percentage points stricter than Euclidean.