Aug 23 2008
GPS vs AGPS
GPS (Global Positioning System) vs AGPS (Assisted Global Positioning System. Which is better for a mobile phone user. Here’s an attempt to understand:
Sprint describes how their system is supposed to work from their online FAQ:
Q: What is Assisted GPS? How do you find me if only two satellites are available?
A: To meet the defined industry standards, a precision location fix requires a minimum of three GPS measurements. The term “Assisted” refers to how Sprint network resources are used to provide a more robust measurement when only two satellites are visible.
Precision fix in tens of seconds.
Very High accuracy (typically 5m-50m).
Line of sight to three satellites is not required as in regular GPS technology, but two satellites must be visible for a precise AGPS fix.
GPS chipset required in device. (All Sprint phones sold since Jan 2002 have the GPS chipset. Contact your Sprint account representative for additional information.)
This is why many of us in the forums often cringe when someone suggests that having a standalone SiRFIII chip in a phone is preferable to an aGPS system, although the confusion is quite understandable and that brings us to our next point: the caveats.
more here
