Over the weekend I added a little content to the “Math for Maps” chapter of the OSGeo's Free GIS Book. It's the short introduction to the section in the chapter that is about the measurements made to create maps or spatial data.
You find the chapter here:
I'll start on the measurements section of the chapter next weekend, with some material on measuring distances. Hopefully I'll have time to write a couple of sample problems.
The Sunburned Surveyor