A hike in the White Mountains might be your antidote to a life dominated by screens, buzzes and dings. But a cell phone can be lifesaving if you've lost your way on the trail. In fact, the Civil Air Patrol uses cell phones to help find lost hikers. NHPR's Peter Biello spoke with Granite Geek David Brooks, a reporter for the Concord Monitor, about this technology.
(This transcript has been lightly edited for clarity.)
First, what is the Civil Air Patrol?
The Civil Air Patrol is actually a volunteer, it's a civilian auxiliary, sort of an arm of the U.S. Air Force. It was created to spot submarines in World War II actually but now it does mostly search and rescue. So these are people that if there's somebody lost one of the things they do is they call the Civil Air Patrol and volunteers jump either into their own planes or I think the CAP has some of their own and start flying a grid while somebody is looking down from above trying to find you.
You talked with someone from the Civil Air Patrol about a rescue mission that was done in the White Mountains in May. How did they go about using cell phone information to find this person?
That rescue got a fair amount of coverage because the victim, when they finally got to him, had to be helicoptered out because he was so close, frankly, to dying of the cold. And as part of the coverage it talked about cell phone forensics. And I was interested as to what cell phone forensics was because I sort of thought the cell phone would tell you where you are and there didn't seem to be much forensics to it.
Right, because cell phones sort of have a location piece in them that can tell you where you are at all times?
Except they don't and that's where it gets interesting, that's where the forensics comes in. So cell phone 101, abbreviated, is when your phone sends out a signal in all directions looking for a tower, it goes to a tower and tries to connect and maybe it will connect. Maybe it won't connect because that tower is already full or maybe it won’t connect because the signal is so weak because there's a bunch of trees and hills and you can just barely see it. So it connects to the next tower it can find. This is why you can't tell from the tower location where the phone is.
If you can't tell from the tower where exactly a cell phone may be, how can you tell?
You can't tell only from the tower. The Civil Air Patrol, as part of its search and rescue, has created a cell phone forensics unit. So one of the things it has for example is detailed geographic cellular tower maps. You look at a cell tower on a map and it's got a circle around it and says the signal goes there. You and I know if we’re in the north that sometimes the signal doesn't go there because the mountains are in the way.
So the CAP cell phone forensics team has a very detailed map about where the tower’s signal actually goes and it uses other information like which one of the antennas on the tower gets it. So they factor in all those things. They crunch it and they say, “It's likely that the last call originated from within a box.” And that box can be very small and that box can be pretty big.
What happened in the most recent case, for example, the one I'm talking about, is that the man was actually found about 90 yards from what the forensics team said was his most likely last location, which is pretty darn good. It's not always that precise but in this case it made the difference between life and death.
If we're hiking and we have a cell phone with us and find that we're lost, should we leave it on or should we make a phone call? What should we do?
You should call 911. The reason for that is, even though you don't want to call 911 because it feels like you're going overboard, call 911. Because 911 under federal law has GPS attached to it and GPS, because it uses satellites instead of cell phone towers, can pinpoint you. They sometimes tell people, “Don't call 911 because I've got a connection with you right now and you’ll have to hang up and dial it and I might lose you.” Call 911 every time because that's the best chance of getting GPS which is the best at locating.
David Brooks is a reporter for the Concord Monitor and the writer who can easily pinpoint geeky topics from miles away without the use of modern technology at GraniteGeek.org.