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

Executing DEM operations


PostGIS comes with several functions for use on digital elevation model (DEM) rasters to solve terrain-related problems. Though these problems have historically been in the hydrology domain, they can now be found elsewhere; for example, finding the most fuel-efficient route from point A to point B or determining the best location on a roof for a solar panel. PostGIS 2.0 introduced ST_Slope(), ST_Aspect(), and ST_HillShade() while PostGIS 2.1 added the new functions ST_TRI(), ST_TPI(), and ST_Roughness(), and new variants of existing elevation functions.

Getting ready

We will use the SRTM raster, loaded as 100 x 100 tiles, in this chapter's first recipe. With it, we will generate slope and hillshade rasters using San Francisco as our area of interest.

The next two queries in the How to do it section use variants of ST_Slope() and ST_HillShade() that are only available in PostGIS 2.1 or higher versions. The new variants permit the specification of a custom extent to constrain...