Assisted GPS (abbreviated generally as
A-GPS and less commonly as
aGPS) is a system that often significantly improves startup performance—i.e.,
time-to-first-fix (TTFF), of a
GPS satellite-based positioning system. A-GPS is extensively used with GPS-capable
cellular phones, as its development was accelerated by the U.S.
FCC's
911 requirement to make cell phone location data available to emergency call dispatchers.