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

Simplifying geometries with PostGIS topology


In a previous recipe, we used the ST_SimplifyPreserveTopology function to try to generate a simplification of a polygonal PostGIS layer.

Unfortunately, while that function works well for linear layers, it produces topological anomalies (overlapping and holes) in shared polygon borders. You used an external toolset (GRASS) to generate a valid topological simplification.

In this recipe, you will use the PostGIS topology support to perform the same task within the spatial database, without needing to export the dataset to a different toolset.

Getting ready

To get started, perform the following steps:

  1. Be sure that you have PostGIS topology support enabled in your database instance. This support is packaged as a separate extension and, if you are using PostgreSQL 9.1 or newer versions, you can install it using the following SQL CREATE EXTENSION command:
postgis_cookbook=# CREATE EXTENSION postgis_topology;
  1. Download the administrative area archive for Hungary...