Sprint Nextel U727 - Manual (Page 86)

78 Section 2C: Menu Options
Location-Based Services use Advanced Forward Link
Trilateration (AFTL) while you are indoors or when there are
no satellites in view. AFTL is a type of handset-based position
location technology. Unlike A-GPS, AFLT does not use GPS
satellites to determine location. To determine location, your
device takes measurements of signals from nearby cellular
base stations (towers) and reports the time and distance
readings back to the network, which are then used to
triangulate an approximate location of the device. In general,
at least three surrounding base stations are required to get
an optimal position fix.
Note: AFLT is only used while indoors or when satellites are not in
view. AFLT accuracy is limited by the geometry of the cell
towers surrounding the device requesting location
information.
If you are outside you may be able to obtain an updated GPS
fix more often than once an hour depending on the level of
visibility.
Weather conditions may also limit your ability to acquire a
GPS fix while outside.