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	Network Distance Analysis	Isochrone Analysis
Ämnesområde	Human Geography	Human Geography
Familj	Process / pipeline	Process / pipeline
Ursprungsår	1959	1959
Upphovsperson	Edsger W. Dijkstra (shortest-path foundation)	Edsger W. Dijkstra (shortest-path foundation)
Typ	Measurement of distance and travel cost along a network rather than straight-line	Computation of travel-time contours reachable from a location on a network
Ursprungskälla	Dijkstra, E. W. (1959). A note on two problems in connexion with graphs. Numerische Mathematik, 1(1), 269–271.	Dijkstra, E. W. (1959). A note on two problems in connexion with graphs. Numerische Mathematik, 1(1), 269–271.
Alias	Shortest-Path Analysis, Network Travel-Cost Analysis, OD Cost Matrix Analysis, Routing Distance Analysis	Travel-Time Analysis, Isochrone Mapping, Service Area Analysis, Travel-Time Contours
Närliggande	4	4
Sammanfattning	Network distance analysis measures how far apart places are along a real network — roads, paths, rails — rather than as the crow flies, recognizing that movement is constrained to edges and junctions. Its engine is the shortest-path problem solved by Dijkstra's 1959 algorithm, which finds the least-cost route between locations over a weighted graph and scales up to origin–destination cost matrices between many points. Network distance and travel time are the realistic inputs to accessibility, routing, location, and flow analyses, and their ratio to straight-line distance — the detour or circuity index — itself diagnoses how indirect a network is.	Isochrone analysis computes the area reachable from a location within a given travel time, drawing contour lines — isochrones — that enclose everywhere you can get to in, say, 15, 30, or 45 minutes. It rests on the single-source shortest-path problem solved by Dijkstra's 1959 algorithm: from an origin, the travel time to every node of a routable network is found, thresholded, and converted into a polygon of reachable space. Isochrones turn an abstract travel-time field into an intuitive map of reach, and underpin service-area planning, accessibility measurement, and location analysis.