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

Merging polygons using a common attribute


There are many cases in GIS workflows where you need to merge a polygonal dataset based on a common attribute. A typical example is merging the European administrative areas (which you can see at http://en.wikipedia.org/wiki/Nomenclature_of_Territorial_Units_for_Statistics), starting from Nomenclature des Units Territoriales Statistiques (NUTS) level 4 to obtain the subsequent levels up to NUTS level 1, using the NUTS code or merging the USA counties layer using the state code to obtain the states layer.

PostGIS lets you perform this kind of processing operation with the ST_Union function.

Getting ready

Download the USA countries shapefile from the https://nationalmap.gov/ website at http://dds.cr.usgs.gov/pub/data/nationalatlas/co2000p020_nt00157.tar.gz (this archive is also included in the code bundle provided with this book) and import it in PostGIS as follows:

$ ogr2ogr -f PostgreSQL -s_srs EPSG:4269 -t_srs EPSG:4326 -lco GEOMETRY_NAME=the_geom ...