Book Image

PostGIS Cookbook - Second Edition

By : Pedro Wightman, Bborie Park, Stephen Vincent Mather, Thomas Kraft, Mayra Zurbarán
Book Image

PostGIS Cookbook - Second Edition

By: Pedro Wightman, Bborie Park, Stephen Vincent Mather, Thomas Kraft, Mayra Zurbarán

Overview of this book

PostGIS is a spatial database that integrates the advanced storage and analysis of vector and raster data, and is remarkably flexible and powerful. PostGIS provides support for geographic objects to the PostgreSQL object-relational database and is currently the most popular open source spatial databases. If you want to explore the complete range of PostGIS techniques and expose related extensions, then this book is for you. This book is a comprehensive guide to PostGIS tools and concepts which are required to manage, manipulate, and analyze spatial data in PostGIS. It covers key spatial data manipulation tasks, explaining not only how each task is performed, but also why. It provides practical guidance allowing you to safely take advantage of the advanced technology in PostGIS in order to simplify your spatial database administration tasks. Furthermore, you will learn to take advantage of basic and advanced vector, raster, and routing approaches along with the concepts of data maintenance, optimization, and performance, and will help you to integrate these into a large ecosystem of desktop and web tools. By the end, you will be armed with all the tools and instructions you need to both manage the spatial database system and make better decisions as your project's requirements evolve.
Table of Contents (18 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Calculating Voronoi diagrams


In the 2.3 version, PostGIS provides a way to create Voronoi diagrams from the vertices of a geometry; this will work only with versions of GEOS greater than or equal to 3.5.0.

The following is a Voronoi diagram generated from a set of address points. Note how the points from which the diagram was generated are equidistant to the lines that divide them. Packed soap bubbles viewed from above form a similar network of shapes:

Voronoi diagrams are a space-filling approach that are useful for a variety of spatial analysis problems. We can use these to create space filling polygons around points, the edges of which are equidistant from all the surrounding points.

Note

More information about Voronoi diagrams can be found at the following link:http://en.wikipedia.org/wiki/Voronoi_diagram

The PostGIS function ST_VoronoiPolygons(), receives the following parameters: a geometry from which to build the Voronoi diagram, a tolerance, which is a float that will tell the function...