Daily Kos: how Verizon tells the FBI where you are

The FBI's court order requires Verizon to hand over all "call detail records or "telephony metadata" — including local telephone calls.
     Here's how creepy that order really is, according to the Daily Kos:

     This includes "comprehensive communications routing information," along with the "Internation Mobile station Equipment Identity (IMEI) number" and the "trunk identifier."
     ForeignPolicy.com brought in Allan A. Friedman, a techie from the Brookings Institution to explain this jargon.

According to Friedman, it might include, for example, data tracking how a cell phone user moves from one cell phone tower to another while traveling -- information that would obviously be useful for tracking the whereabouts of an individual.

And likewise with "trunk identifier."

The trunk identifier provides additional data on how a call is routed through a telephone system and where it originated. In a landline system, for example, the trunk identifier can be used to identify the regional center through which a call is routed.

The same trick works for mobile phones, as explained by Wikipedia in this hash of acronyms.

The MSC (Mobile Switching Center) is connected to a close telephone exchange by a trunk group. This provides an interface to the (Public Switched Telephone Network) (PSTN). It also provides connectivity to the PSTN. The region to be served by a Cellular Geographic Serving Area(CGSA) is split into geographic cells.

So the feds can track all Verizon customers at least within the limits of a "Cellular Geographic Serving Area,"with a radius of about 3 miles, and then within a "cell" of that area.