GPS was originally developed for the military.
24 satellites positioned around the Earth in order to give soldiers a precise location at any given time. These signals were encrypted and still are. (I think)
But its interesting to know there are a number of companies building and selling GPS devices openly.
They have become as common as a wrist watch and more than likely you can get a GPS built into a wrist watch.
The courts in Canada @ one point said it was illegal for example to receive programming from US providers on the basis that it is illegal to decrypt encrypted signals. If this is the case,isnt every one who owns or manufactures GPS devices criminals?