Chapter 7. Working with real data
This chapter covers
In the prior chapters we explored many of the functions provided in PostGIS by creating our own test data and also discussed spatial reference system considerations for data. In this chapter we’ll cover how to load real data and export it. You can find free geographic data to load in your database in numerous locations. Geographic data that covers large areas on a spheroidal earth needs a little special care. You’ll need to understand, at least on a rudimentary level, ellipsoids, datums, and projections to be able to understand the pros and cons of each spatial reference system and determine which ones are suitable for your use case. We hope the fundamentals of these we provided in the last chapter are sufficient to help you handle working with real data.
Before we begin our exercises, you need to know where you can get free data to play with. Locations for free data can be found in appendix A. In the next section, we’ll briefly cover some of the more popular free and open source tools, both packaged and not packaged with PostGIS, that are useful for importing and exporting data.
Many tools are available for getting data into and out of PostgreSQL/PostGIS. For this chapter, we’ll focus on only the more common free and open source tools.