I am interested in GPS devices. I want to know how they work and if I need to purchase something like an annual subscription for them. For example, this is a unit I’m looking at: http://www.newegg.com/Product/Product.aspx?Item=N82E16858108362
you do not need any subscription to use the satellites.
just say thanks to the US of A.
and what functions such a GPS unit has?
The Garmin page, https://buy.garmin.com/shop/shop.do?pID=13427&ra=true, will have more info on the specific functions of that GPS nav. But basically it connects to , i think, twelve to twenty four satellites depending on the unit to triangulate you position. It is on perfectly accurate, as the US Gov. doesn't want them too good.
Nope, The satellites use for these devices are owned and operated by the US Gov.