QUANTIFYING URBAN VISIBILITY USING 3D SPACE SYNTAX
C. Schroder, W. Mackaness, F. Reitsma
Urban landscapes can be characterised in many different ways. A systematic way of describing different types of spaces and their qualities is useful to urban planners and architects. The focus of this paper is on methods to describe the degree of visibility within an urban landscape. Some spaces make the pedestrian feel closed in, whilst other spaces are attractive because of their open vistas, giving a feeling of connectedness with the rest of the city. There are two parts to visibility mapping – the first is a model that enables the measurement of visibility, and the second is how such information is then visualised. The methodology used was inspired by ideas from space syntax – a set of metrics devised to measure connectedness of urban spaces. Since its inception, space syntax methods and techniques have treated the world as being in two dimensions (thus not taking into account the height of buildings, nor the changing height of the underlying surface upon which the buildings sit). This work extends space syntax into the third dimension, enabling researchers to fully understand the effect that the surrounding area has on the social processes operating within urban landscapes. This paper presents two newly developed ideas, the idea of a 3D space syntax and a resulting visibility surface. Extending the space syntactic idea to incorporate both the layout of the urban form and its height allows researchers to analyse the effect that topographical characteristics have on space. Extended 3D axial lines are developed to take into account the extent and height of block space. The slopes of the 3D axial lines are used as the basis for constructing a visibility surface. As well as extending the application of space syntax into 3D worlds, the method offers a new way of visualising visibility within urban landscapes. The paper will present the methodology in more detail, and explain a broader set of applications that extend beyond the cartographic.