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

Translating, scaling, and rotating geometries – advanced


Often, in a spatial database, we are interested in making explicit the representation of geometries that are implicit in the data. In the example that we will use here, the explicit portion of the geometry is a single point coordinate where a field survey plot has taken place. In the following screenshot, this explicit location is the dot. The implicit geometry is the actual extent of the field survey, which includes 10 subplots arranged in a 5 x 2 array and rotated according to a bearing.

These subplots are the purple squares in the following diagram:

Getting ready

There are a number of ways for us to approach this problem. In the interest of simplicity, we will first construct our grid and then rotate it in place. Also, we could in principle use a ST_Buffer function in combination with ST_Extent to construct the squares in our resultant geometry, but, as ST_Extent uses floating-point approximations of the geometry for the sake of efficiency...