Isovist_2.0
McElhinney, Sam (2017) Isovist_2.0. Canterbury School of Architecture, Canterbury, UK.
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Isovist_2.0 (http://www.isovists.org) is a free, multi-platform, software tool. It performs visibility analysis ‘scans’, that assist architectural practitioners and researchers in better understanding spatial coherence and structure within the built environment. It can be operated at any scale, from individual rooms to urban street patterns. The tool uses the spatial unit of the ‘isovist’ (Benedikt, 1979) to extract metrics of geometry and intervisibility without requiring computationally lengthy graph analysis. The resulting ‘scans’ allow researchers or practitioners to intuitively and empirically identify experientially, navigationally or socially significant affordances within existing or proposed spatial environments.
Isovist_2.0 provides seven measures, with numerous sub-categorisations. Two are ‘global’ integration measures that quantify overall spatial relations within a plan, matching established Space Syntax methodology; of these, 'mean metric depth' identifies the average distance from all points in a plan to all others (Hillier, 2009) whilst 'mean visual depth' identifies the average number of visual steps from all points in a plan to all others (Hiller, 1996). The remainder provide 'local' isovist measures that quantify rates of change of the visual field within a plan or isolate transformations in configurational geometry that relate to occupant experience. Said measures are (from any given location), Connectivity, or isovist area (Benedikt, 1979); Compactness, the isoperimetric ratio of shape of space; Drift, the distance between the location from which the isovist is generated and the centre of gravity of the isovist (Dalton & Dalton 2001); Occlusivity, the ratio of length of unbounded isovist edge to isovist area (Benedikt, 1979); and Vista, the longest length of view.
Isovist_2.0 outputs coloured plan diagrams and quantitative point data for further statistical analysis. These are an alternative to the visibility graph analysis of the widely adopted DepthMapX software (Turner et al, 2001); but Isovist_2.0’s data is achieved at circa 25 times the resolution in 1/60th the calculation time (McElhinney, 2017).
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