When it comes to GIS, the first thing that comes to mind is where something is located. Once you can
locate places using a set of coordinates, questions such as the following arise, which always involve some
kind of distance calculation: How far is my house from the nearest expressway? How many pizza joints
are within a mile drive? What’s the average distance that people have to commute to work? What are the 10 closest parks to me? How many people live in my city and make more than me?
In this chapter we’ll cover the key functions and operators PostGIS provides for doing proximity analysis. These
functions are the foundation of most location based queries. We’ll also cover the various options
limitations based on which spatial type you choose wheter it be geometry or geography.
Stay tuned for our next book pgRouting: A Practical Guide published by Locate Press due out in hard-copy 4th quarter 2017. Content is now feature complete and can purchase e-Book draft and get final when goes to print.
© Leo Hsu and Regina Obe 2014