E911 compliance, a.k.a. location-capable, was mandatory by Dec. 31, 2005. This made wireless carriers provide phones that used the E911 service to relay coordinate location data of callers to within roughly just shy of 1,000 feet for emergency calls.

The minimum of number towers to relatively fix a position is two. This is called the AOA (angle of arrival). Another is TDOA (time difference of arrival) which is multilateration. And then there’s location signatures but I won’t even get into that (takes too long to explain).

Contrary to popular belief, GPS is not worthless indoors any longer. Things like WAAS, SiRF and ephemeris data prediction (mostly) fixed that; it depends what GPS tech is within the wireless phone.

In addition, some carriers used GPS while others use A-GPS – which was specifically developed for E911 use.

Signal gain drops with the inverse square of the distance from the source. This is how gain is converted into distance and therefore how a line of position (LOP) is electronically drawn.

ALL cellphone locations can be tracked to within a few hundred meters by the signal strength (gain) that is being received by the nearest cell phone transceiver towers. This is especially true in urban environments where there are more cellphone transceivers per square mile.

If you understand navigation, you understand how triangulation works. Where the lines of position intersect, this is close to where you are. The signal strength that three towers are receiving can be converted to three arcs, and where those arcs intersect is where you are very close to.

It does not matter whether or not your cellphone has an embedded GPS. You can be tracked by the method I described regardless. Not only can it be done, it is done.

Also, GPS is worthless indoors unless you are standing right next to a window. This of course is not true with cellphones. Its easy to track you indoors as well.