ABSTRACT
Early GIS projects represented the real world as two-dimensional (2D) map coordinates (X, Y), in no small part because of the technical difficulties of dealing with the third (Z) dimension. Many of the earliest attempts at GIS modelling were little more than 2D map analysis (Longley et al., 2005) and this remains the ‘bread and butter’ of much of today’s work. For example, Figure 1.1 shows a simple site suitability project for San Diego County, USA that is based on 2D map analysis. A simple cartographic model takes roads and vegetation as input (blue ellipses), creates a buffer around the roads, and combines the road buffer with vegetation (yellow boxes) to create a map of the vegetation types affected by the proposed roads (green ellipse). The proposed roads (red lines) and buffers (light blue) are shown on the map. This is obviously a very simple example, but the basic approach
illustrated here has been used many times to create quite sophisticated process models with hundreds of inputs and transformation tools.
