手法を比較

	Catchment Area Analysis	Two-Step Floating Catchment Area
分野	Human Geography	Human Geography
系統	Process / pipeline	Process / pipeline
提唱年	1964	2003
提唱者	David L. Huff (probabilistic formulation)	Wei Luo & Fahui Wang
種類	Delineation of the geographic area served by a facility	Spatial accessibility measure for competition over constrained services
原典	Huff, D. L. (1964). Defining and estimating a trading area. Journal of Marketing, 28(3), 34–38.	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.
別名	Trade Area Analysis, Service Area Delineation, Market Area Analysis, Catchment Delineation	2SFCA, Floating Catchment Area Method, Enhanced Two-Step Floating Catchment Area, 2SFCA Accessibility
関連	4	4
概要	Catchment area analysis delineates the geographic area that a facility — a shop, hospital, school, or station — actually serves, turning the abstract question of 'who uses this place?' into a mapped polygon. Methods range from the simplest fixed-radius buffer through nearest-facility (Voronoi) tessellation and network drive-time isochrones to David Huff's 1964 probabilistic model, in which patronage is shared among competing facilities by their relative attractiveness and distance. The choice of method reflects how strictly customers are tied to the nearest centre and how much competition and travel cost shape real behaviour.	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.