Book Image

PostGIS Cookbook

Book Image

PostGIS Cookbook

Overview of this book

Table of Contents (18 chapters)
PostGIS Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Normalizing imports


Often data used in a spatial database is imported from other sources. As such it may not be in a form that is useful for our current application. In such a case, it may be useful to write functions that will aid in transforming the data into a form that is more useful for our application. This is particularly the case when going from flat file formats, such as shapefiles, to relational databases such as PostgreSQL.

Note

A shapefile is a de facto as well as formal standard for the storage of spatial data, and is probably the most common delivery format for vector spatial data. A shapefile, in spite of its name, is never just one file, but a collection of files. It consists of at least *.shp (which contains geometry), *.shx (an index file), and *.dbf (which contains the tabular information for the shapefile). It is a powerful and useful format but, as a flat file, it is inherently nonrelational. Each geometry is associated in a one-to-one relationship with each row in a table...