Chapter 3. Spatial reference system considerations
This chapter covers
- Characteristics of spatial reference systems
- How to determine and select spatial reference systems
Up to this point we’ve been working mostly with fictitious data. Using sample data to learn the basics of PostGIS is an excellent beginning. You’re immediately rewarded with results without facing the distractions and the obstacles of real-world data. From this chapter forward, though, we’re not going to shield you anymore.
We’ll start this chapter by discussing different types of spatial reference systems. We’ll then follow up with sections on selecting suitable SRSs for storage and on determining the spatial reference of source data.
The art and science of modeling our bulbous earth and getting a 2D representation on paper have been around since antiquity. Geodetics is the science of measuring and modeling the earth, and cartography is the science of representing the earth on flat maps. The intricacies of these two venerated sciences are far beyond the scope of this book, but together with a lot of math, they produce something that’s of utmost importance to GIS: spatial reference systems (SRSs).