手法を比較

	Two-Step Floating Catchment Area	Accessibility Analysis
分野	Human Geography	Human Geography
系統	Process / pipeline	Process / pipeline
提唱年	2003	1959
提唱者	Wei Luo & Fahui Wang	Walter G. Hansen
種類	Spatial accessibility measure for competition over constrained services	Spatial index of the ease of reaching opportunities from a location
原典	Luo, W., & Wang, F. (2003). Measures of spatial accessibility to health care in a GIS environment: synthesis and a case study in the Chicago region. Environment and Planning B: Planning and Design, 30(6), 865–884.	Hansen, W. G. (1959). How accessibility shapes land use. Journal of the American Institute of Planners, 25(2), 73–76.
別名	2SFCA, Floating Catchment Area Method, Enhanced Two-Step Floating Catchment Area, 2SFCA Accessibility	Hansen Accessibility, Gravity Accessibility Measure, Potential Accessibility, Spatial Accessibility Index
関連	4	4
概要	The two-step floating catchment area (2SFCA) method measures spatial accessibility to constrained services — most famously physicians and hospitals — by accounting not only for how close supply is but for how many other people are competing for it. Introduced by Wei Luo and Fahui Wang in 2003, it works in two passes: first computing a supply-to-demand ratio at every service location, then summing those ratios over all services within reach of each population site. The result is a single accessibility score per location that captures both proximity and crowding, and it has become the standard measure of access to healthcare and other capacity-limited services.	Accessibility analysis measures how easily opportunities — jobs, shops, clinics, parks — can be reached from a given location, combining the attractiveness (size) of destinations with the cost of travelling to them. The gravity-based formulation introduced by Walter Hansen in 1959 sums the opportunities at all destinations, each discounted by a distance-decay function of travel cost, producing a single accessibility score per origin that has become a foundational concept in transport geography and urban planning.