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

Clipping geometries to deploy data


A common GIS use case is clipping a big dataset into small portions (subsets), with each perhaps representing an area of interest. In this recipe, you will export from a PostGIS layer representing the rivers in the world, with one distinct shapefile composed of rivers for each country. For this purpose, you will use the ST_Intersection function.

Getting ready

Be sure that you have imported in PostGIS the same river dataset (a shapefile) that was used in the previous recipe.

How to do it...

The steps you need to take to complete this recipe are as follows:

  1. First, you will create a view to clip the river geometries for each country using the ST_Intersection and ST_Intersects functions. Name the view rivers_clipped_by_country:
       postgis_cookbook=> CREATE VIEW chp03.rivers_clipped_by_country AS 
         SELECT r.name, c.iso2, ST_Intersection(r.the_geom,
           c.the_geom)::geometry(Geometry,4326) AS the_geom
         FROM chp03.countries AS c 
     ...