GIS Fundamentals, 2nd Edition

Chapter 5

Vector Algorithms for Areas

5.1 Calculations on Areas: Single Polygons

We saw in Chapter 3 that area features are stored in GIS as polygons, represented using a single closed line, or a set of connected links. In this chapter, we are going to consider some of the fundamental operations involving areas in GIS, starting with finding out how large an area is.

For the moment, we will assume that the polygon is stored in the simplest possible form – as a line which closes on itself like the example in Figure 5.1.

Figure 5.1

Single polygon.

This line is stored as a series of five points which form the ends of the five straight segments. ...