here is my 2 cents on how assisted gps needs a data plan. The satellite and agps server work together. The satellite locks ur current location and send the data to the agps server(lets make sprint server as an example).sprint server then uploads ur current location on ur phone.This is posible if ur on the sprint data network. And in order to get in the sprint network, U need a data plan or else be charged per KB. Now after U download ur current location from sprint server,ur preloaded map will have the info to help U navigate. Remember guys, This is on assisted mode. Not standalone. There a more to this but This is my last post. Like mr.boogie said in his sig."I don't want to spend my life explaining myself. Either you get it or you don't."
edit: IS this completely wrong?
But when you use
assisted GPS this whole process is much faster. Very often cellular network towers have GPS receivers (or a base station nearby) and those receivers are constantly pulling down satellite information and computing the data. This data is then p***** on to the cellular phone (when requested) and acts like a “cheat” since the relevant satellites to your location are already identified and all that GPS computations is handled by 3rd party computers. This is the result of such a system, to you the end user:
- Faster location acquisition
- Less processing power is required by the device
- Saves battery life
- Location acquisition indoors or in non-optimal environmental settings
See for more info:
http://wmexperts.com/articles/gps_vs..._tutorial.html