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

Sharing and visualizing rasters through SQL


In Chapter 4Working with Vector Data – Advanced Recipes, we used gdal_translate to export PostGIS rasters to a file. This provides a method for transferring files from one user to another, or from one location to another. The only problem with this method is that you may not have access to the gdal_translate utility.

A different but equally functional approach is to use the ST_AsGDALRaster() family of functions available in PostGIS. In addition to ST_AsGDALRaster(), PostGIS provides ST_AsTIFF(), ST_AsPNG(), and ST_AsJPEG() to support the most common raster file formats.

To easily visualize raster files without the need for a GIS application, PostGIS 2.1 and later versions provide ST_ColorMap(). This function applies a built-in or user-specified color palette to a raster, that upon exporting with ST_AsGDALRaster(), can be viewed with any image viewer, such as a web browser.

Getting ready

In this recipe, we will use ST_AsTIFF() and ST_AsPNG()to export...