BEN LEVITAN, TELECOMMUNICATIONS EXPERT (via telephone): Nancy, if the cell phone was on, it was easy to do. You know (INAUDIBLE) dial 911,
Nancy. The cell phone company can determine your location within 100 feet. Now, law enforcement has been using this for the past couple years also to
track people. We can send a signal to a cell phone, and it will come back with a location within 100 feet.
Now, Nancy, if her phone was off, we can look at her cell phone records and determine what cell tower she was close to. And frankly, if
the suspect`s phone was in those same cell tower locations, it probably gave the police a clue as to who to look for and where the body possibly
was. So when her phone was last used, if it was in the same cell tower location as the suspect, then they probably had a search area of about
three square miles. If that phone was on, Nancy, they could pinpoint it down to 100 feet.
GRACE: With me, Ben Levitan, telecommunications expert. So let me get this straight. Even if your cell phone goes dead, you leave it on and
it goes dead, the police can find the last known ping before the cell phone went dead? They could go back and look at those pings? They don`t have to
look at pings in realtime, they can go back and look at the last ping, and if it was there at Argos cement factory, then they would know?
LEVITAN: Generally, you can know what cell tower it was last at. And that`s an area probably about three square miles. And if in that three
square miles was a cement factory and it`s the known workplace of the suspect, that would be an obvious place to look.
http://transcripts.cnn.com/TRANSCRIPTS/1410/01/ng.01.html
This guy gave a good explanation how they may have connected the pings to pinpoint the location. Once they realized this guy used to work at the concrete place it probably fell into place for them.