This week we’re going to look at how to choose a coordinate
system for your database. In PostGIS, this includes the choice
of geometry vs geography columns, as well as which projection
(if any) to use, and how to interact with it from Rails. In this
article, we’ll: - Review geographic and projected coordinate
systems - Discuss the pros and cons of using the PostGIS
geographic type - See why I typically store data in a projection
- Look at some specific projections I recommend using (or
avoiding) - Learn how to handle projected data in Rails My
original series plan for this week called for a worked example
of a location-based web service, bringing together much of the
material that we’ve covered so far. But as I was writing it, I
realized there was one more topic we probably ought to cover
first. So I’ll publish the example next week. This is part 7 of
my continuing series of articles on geospatial programming in
Ruby and Rails. For a list of the other installments, please
visit http://www.daniel-azuma.com/blo