Introduction

The landscape metaphor central to the Part is less appropriate to urban environments that are largely composed of built forms. In digital terms, built environments lie at the intersection between geography and geometry. Their definition is largely one involving the three-dimensional (3D) representation of buildings and streets where the underlying two-dimensional (2D) map structure is usually implicit rather than explicit. What geography brings to these virtual realities is an explicit link between the 2D map and the 3D form. Currently this relationship is best seen in the way GIS software is beginning to incorporate the third dimension, notwithstanding the problems posed by different data structures that dominate the 2D and 3D worlds discussed in earlier chapters in this book. The types of environment that form the material of this section of the book are admirably illustrated by the numerous contemporary digital realisations of complex urban scenes, one of which – population density in Westminster in central London – is illustrated in Figure 15.1.