Glossary

Key terms used throughout this guide.

Accessibility

A measure of how easily land uses (shops, parks, restaurants, etc.) can be reached from each point in the street network. Computed using network distance, not straight-line distance. See Accessibility recipes and compute_accessibilities.

Beta / Spatial Impedance

A decay parameter that controls how quickly the influence of distant features diminishes. Higher beta values mean sharper distance decay. When not specified explicitly, cityseer derives betas automatically from the distance thresholds. See the API documentation.

Betweenness Centrality

Counts how often a node (or street segment) lies on the shortest paths between all other pairs of nodes. High betweenness indicates streets that serve as major through-movement corridors. See Centrality recipes.

Closeness / Harmonic Centrality

Measures how close a node is to all other reachable nodes. The harmonic variant sums the inverse distances, making it robust to disconnected components. Higher values indicate more central, well-connected locations.

Continuity

Assesses how consistently named routes, road classifications, or route numbers extend through the network. Useful for understanding legibility and identifying major through-routes. See Continuity recipes.

CRS / EPSG

A Coordinate Reference System defines how geographic coordinates map to locations on the Earth’s surface. EPSG codes are numeric identifiers for specific CRS definitions (e.g., EPSG:4326 for WGS 84 longitude/latitude, EPSG:3035 for ETRS89-LAEA Europe). Always use a projected CRS (with metre units) for distance and area calculations.

Density (Network)

Counts the number of other nodes reachable within a given network distance threshold. A simple measure of how well-connected a location is at a particular scale.

Dual Graph

A graph representation where streets become nodes and intersections become edges. This is the inverse of a primal graph. Working with the dual graph is recommended for centrality analysis because it expresses metrics relative to street segments rather than intersections. See nx_to_dual.

Edge Rolloff

A boundary distortion effect that occurs when the network does not extend far enough beyond the study area. Nodes near the boundary have fewer reachable destinations, producing artificially low metric values. Prevent this by buffering the network and setting boundary nodes to live=False. See the Edge Rolloff section.

Live Nodes

Nodes with live=True are within the study area and will have metrics computed. Nodes with live=False exist in the buffer zone — they are used for routing (preventing edge rolloff) but their results are excluded from output. See the Edge Rolloff section.

Mixed-Use

A measure of the diversity of land uses reachable from each node within a given distance threshold. Higher mixed-use values indicate areas where many different types of amenities are accessible. See compute_mixed_uses.

Network Distance

The shortest-path distance along the street network between two points, as opposed to Euclidean (straight-line) distance. All cityseer metrics use network distance by default.

NetworkStructure

A cityseer data structure (backed by Rust) that holds the network topology for efficient metric computation. Created from a networkx graph using network_structure_from_nx. Can be reused across multiple metric calculations as long as the network doesn’t change.

Primal Graph

The conventional graph representation where intersections are nodes and streets are edges. This is the default output from most network creation functions. Convert to a dual graph using nx_to_dual for street-level centrality analysis.

Visibility

Measures how enclosed or open the street environment is at each point, based on surrounding built form. Computed by casting rays from network nodes and measuring how far they travel before hitting a building or obstruction. See Visibility recipes.