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PostGIS Cookbook

You're reading from   PostGIS Cookbook For web developers and software architects this book will provide a vital guide to the tools and capabilities available to PostGIS spatial databases. Packed with hands-on recipes and powerful concepts

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Product type Paperback
Published in Jan 2014
Publisher
ISBN-13 9781849518666
Length 484 pages
Edition Edition
Languages
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Table of Contents (18) Chapters Close

PostGIS Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
1. Moving Data In and Out of PostGIS FREE CHAPTER 2. Structures that Work 3. Working with Vector Data – The Basics 4. Working with Vector Data – Advanced Recipes 5. Working with Raster Data 6. Working with pgRouting 7. Into the Nth Dimension 8. PostGIS Programming 9. PostGIS and the Web 10. Maintenance, Optimization, and Performance Tuning 11. Using Desktop Clients 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 red 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 screenshot:

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 an 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 efficiency...

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