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PostGIS Cookbook

PostGIS Cookbook - Second Edition

By : Vincent Mather, Pedro Wightman, Park, Thomas Kraft, Mayra Zurbarán, Corti
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PostGIS Cookbook

PostGIS Cookbook

3 (4)
By: Vincent Mather, Pedro Wightman, Park, Thomas Kraft, Mayra Zurbarán, Corti

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 (14 chapters)
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Converting between rasters and geometries


In the last recipe, we used the geometries to filter and clip rasters only to the areas of interest. The ST_Clip() and ST_Intersects() functions implicitly converted the geometry before relating it to the raster.

PostGIS provides several functions for converting rasters to geometries. Depending on the function, a pixel can be returned as an area or a point.

PostGIS provides one function for converting geometries to rasters.

Getting ready

In this recipe, we will convert rasters to geometries, and geometries to rasters. We will use the ST_DumpAsPolygons() and ST_PixelsAsPolygons() functions to convert rasters to geometries. We will then convert geometries to rasters using ST_AsRaster().

How to do it...

Let's adapt part of the query used in the last recipe to find out the average minimum temperature in San Francisco. We replace ST_SummaryStats() with ST_DumpAsPolygons(), and then return the geometries as WKT:

WITH geoms AS (SELECT ST_DumpAsPolygons(ST_Union...
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PostGIS Cookbook
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