How AGPS works
I just bought a new Palm Pre smart phone that has a gps receiver built in to it. The really interesting thing about this is that the device uses AGPS or Assisted GPS to increase the number of places where the GPS feature works and to also reduce the amount of time you stare at the GPS screen while you wait for the phone to figure out where it is after turn it on.
This phone is much quicker to show a location than my old phone, so being the curious type I did a little research. Turns out assisted GPS is exactly what it sounds like. My service provider provides assistance data to my phone when it needs it to speed up time to first fix or to increase the sensitivity. This can be an initial cell site sector position to roughly locate the phone, which allows the phone to figure out what satellites to look for or it could be a combination of that plus updated ephemeris data. I know I’m lapsing into geek speak, so this all can be summarized as the cellular network helping the gps stuff in the phone figure out where it is more quickly.
