PostGIS in Action, Second Edition

Chapter 13. Building and using topologies

This chapter covers:

What a topology is

Creating a topology

Building topogeometries

Loading and editing topogeometries

Simplification and validation

Topological representation recognizes that, in reality, geometric features rarely exist independently of each other. When you gaze down on large metropolises from a plane, you see a maze of streets outlining blocks, interlocked. With a simple geometry model, you could use linestrings to represent the streets and polygons to represent the blocks. But once you lay out the streets, you know right where your blocks will be. Having to create polygons for the blocks is an exercise in redundancy. Congratulations, you’ve discovered topology.

In this chapter, you’ll ...