Originally Posted By: Jeff_McCann

I know this is true, but I don't understand the science of it. Why do normal compasses only work in specific zones and what makes "global" compasses different?

Jeff


Here's a good explanation

http://www.dougritter.com/global_needle.htm

The way I understand it, depending where you are on the globe, the needle doesn't always point parallel to the surface of the earth. It could point up or down to some degree. The global needle allows it to pivot without affecting the pointing direction.