Geometrical structure of public spaces in virtual city models. Exploring urban morphology by hierarchy of open spaces

Urban development is now becoming an increasingly complex challenge in global and local terms. The urban form is both, the element of the city's sense and the spatial framework of urban transformations. The morphology of the city is changing constantly with urban development. What can be continuously observed is, that “cities and their complexes grow spatially, forming large areas and absorbing new territories.” [2]. Urban morphology consists of built-up tissue and voids in-between, so the urban development is directly related to the volume and geometrical structure of open areas and public spaces. If the public life occurs in the space in-between, exploring tools of advanced urban analyses focused on morphology of open spaces seems to be important and actual. Spatial disposition and relation between public spaces define unique features of towns and contribute to the general perception of the sense of cities. However the problem is not as obvious as it may seem in practical terms. While the analysis of the built-up tissue of cities is relatively achievable, a measurable analysis of the space in-between is a considerable challenge due to the lack of defined geometry. This geometrical aspect of open spaces in cities is addressed in this article. The promising and powerful data environment enabling the development of such analytic tools are 3D virtual city models. The already introduced by the author analytic method called 3D-Negative (N3D) allows quantification and measurable analyses of the “invisible” geometry. The method is closely related to GIS and cityGML environments. The purpose of the article is to analyze regularities, spatial distribution and structure of public spaces in selected cities in area and linear means.