Parametric analysis of urban form, from geometrical to topological

Résumé 0

This paper presents a methodology to read urban space and to display it through parametric representation. It is based on quantitative analysis of geometrical properties of different urban sequences, parameterized on a sample trajectory representing observer path. A labelled t(x) parameter allows to evaluate such path, systemizing on it visual, spatial, and morphological variations, through some indicators:a. Dimensions D(t): urban space large, measured orthogonally to the observer trajectory tangent at t(x);b. Focal distance Fd(t): visual depth tangent to observer trajectory at t(x);c. Sequences variations: number of dimensions and focal distance deviations greater than respective average value, representing major changes in visual perception along the path, so that they produce the transition from one scene to another one in an urban sequence.Quantitative data depending on a unique parameter t(x) lead to display graphical and statistical representation, as computing of average value, range, and standard deviation.This methodology has been tested on few case studies in European cities: Rome, Palermo, Naples and Barcelona, comparing historical urban fabrics to XIX century planned ones, highlighting constants, differences and variations.The parametrical analysis of sequences indicators allows to shift from geometrical information to a topological model, abstracting results from shape specificity. The configuration pattern linking metric and relational information is experimented as a design pattern. This puts urban analysis in the perspective of design practice, leading to the script of an input matrix for an informed parametric urban modelling.