GPS in Cellphones

Got a question about GPS functionality in cellphones... I don't believe that the GPS circuit is powered if the phone is turned off so I don't believe that a powered-off phone can be "tracked". Beyond that its hard to say because its really up to how the network and phone are configured to work.

Examples:

• my Blackberry has a user option setting to enable and disable the GPS functions, however I believe that the setting gets bypassed during a 911 call, so can probably be bypassed other ways also.
• a couple of years ago when I was working on this it was limited to only while you were on a call because the network needed a "connection" over which to send the location data, but if a service provider wanted to invest some development dollars there would likely be a way to use the "control channels" to transfer the data while the phone was not in a call, but the cost/benefit of this would be questionable since the data bandwidth space available on the control channels is limited so not sure we would waste it on an application that targets individual users (but it is theoretically possible)
• there are less accurate versions that check signal levels received at different towers at the same time from your phone (in a call or idle, during a registration for example) and triangulating your location based on that (this is also done during "assisted GPS" situations where not enough satellites are visible to get an accurate GPS fix)

So, depends why you are asking. Normal commercial operation typically requires an active call and user enable of the service. Can "the man" find you if he really really wants to - probably...