GPS

How the fuck does it work?

Say you buy some handheld gps device, do you have to pay anything to get signals, like a cellphone, or is it free?

Does it work everywhere in the world? How good is the update rate? And doesn't it eat battery power like hell?

>>3
this is how they make money; new maps/maps for other regions are sometimes as expensive as the gps unit itself.  maps are pretty consistent across brands, but "update rate" and "battery life" vary a lot from model to model.  for example, stuff for a car usually has more features as they expect you to always plug it in to recharge, while pocket-sized ones may look shittier but last longer.

there are also simple units that only use raw gps data to tell you your position (latitude/longitude); i guess youd need a separate map to make use of it.