Now we have done a lot with Processing.

But we've only really been working in screen (or paper) space.

If we have a background with a projection Library, we can then put points on a map.

Map Projections could be covered in a GIS course such as EPIC GIS June 2015.

Or read up on via the web or online course.

Q: But remind me why to use Processing for mapping?

A: Because it is extremely powerful, for both 2D and 3D graphics.

We'd likely want to use a Library from Till Nagel, though there may be some others available.