手法を比較

	Sky View Factor Analysis	Isovist Analysis
分野	Urban Studies	Urban Studies
系統	Process / pipeline	Process / pipeline
提唱年	1981	1979
提唱者	Timothy R. Oke (urban-climate application)	Michael L. Benedikt
種類	Pipeline for computing the fraction of visible sky from a point in urban geometry	Geometric analysis of the space visible from a vantage point
原典	Oke, T. R. (1981). Canyon geometry and the nocturnal urban heat island: comparison of scale model and field observations. Journal of Climatology, 1(3), 237–254.	Benedikt, M. L. (1979). To take hold of space: isovists and isovist fields. Environment and Planning B: Planning and Design, 6(1), 47–65.
別名	SVF Analysis, Sky View Factor Mapping, Sky Openness Analysis, Skyview Factor	Visibility Polygon Analysis, Isovist Fields, Viewshed Analysis (Architectural), Visual Field Analysis
関連	4	4
概要	Sky view factor (SVF) analysis quantifies the fraction of the overlying hemisphere of sky that is visible from a given point on the ground, ranging from 1.0 in a wide-open field to near 0 at the bottom of a deep, narrow street canyon. It is a central geometric descriptor in urban climatology because the amount of visible sky governs how much longwave radiation a surface can lose at night, directly shaping the urban heat island. The measure was put on a rigorous footing by Timothy Oke's 1981 work linking canyon geometry to nocturnal urban warming.	Isovist analysis describes the experience of space by computing, for any vantage point, the exact region that is visible from it — the isovist, or visibility polygon. Introduced by Michael Benedikt in 1979, the method turns intuitive notions of openness, enclosure and prospect into measurable quantities such as the area, perimeter and compactness of the visible field. By repeating the construction across a grid of points one obtains an isovist field that maps how visibility varies throughout a building or urban space, making it a core analytic tool in space syntax, architecture and environmental psychology.