By Leslie Cauley
USA TODAY
Copyright 2007 Gannett Company, Inc.
All Rights Reserved
It’s midnight. You’re walking alone to your car deep inside a garage, when you notice you’re being followed. Instinctively, you grab your cellphone and dial 911.
Good move?
The honest answer: probably not as good as you think.
Owing to limitations in Emergency-911 technology, the dispatcher probably won’t be able to pinpoint your location. Unless you can get to a pay phone — not an option in this case — you’ll probably have to give the dispatcher detailed information about your location so emergency personnel can find you.
“Just because you dial 911 on your cellphone, the call-taker doesn’t necessarily know where you are,” warns Bob Gurss, director of legal and government affairs for the Association of Public-Safety Communications Officials (APCO).
To be sure, people who call 911 using cellphones, in many cases, can simply tell the dispatcher where they are. But that’s not always an option, Gurss says.
Sometimes, he says, people don’t know where they are, or they are wrong about their location. Others can’t talk because they are hurt, incapacitated or being victimized by a crime in progress.
“The whole idea of (911) is to be able to get to the location issue without you telling them,” he says.
The problem is getting worse. One big driver is the explosion of wireless calling and the evolution of its use. About 60% of all cellphone calls are made at home, estimates Ford Cavallari, a telecom and media consultant at Monitor Group. Use of a wireless phone as a primary phone is even higher for people 25 or younger, he says.
“People in college don’t have (regular) phones anymore,” he says. “Everybody uses wireless.”
Why is that a problem? Emergency 911, created in 1968, was predicated on the idea that people would call from home or pay phones with fixed addresses that could be fed to the local 911 office, known as a “public safety answer point,” or PSAP. Cellphone technology was still on the drawing board. So nobody worried about how to find people calling from parking garages, apartment stairwells and desolate stretches of highway.
There are two types of systems for wireless 911 access: network-based and GPS (Global Positioning System). Network-based systems use multiple cell sites to get a fix on a caller’s location. GPS systems work off chips in cellphones and determine location from a constellation of low-orbiting satellites. Both have pluses and minuses.
Network-based systems tend to work better in urban areas where cell sites are plentiful. They are less reliable in rural areas, where one site may cover many square miles.
GPS is the opposite. Because it relies on satellite signals, it can be highly accurate in open areas. But it’s less reliable in urban settings where buildings and other structures can block satellite signals. Weather also can be an issue.
Verizon Wireless, which uses GPS, “works dead-on” in rural areas, says spokesman Jim Gerace.
“But if you’re (calling 911) indoors, we suggest customers get close to the window” to improve GPS performance, says Fran Malnati, an executive director. That said, Malnati says, location issues are rarely a problem, because “most of the time, customers know where they’re making the call from.”
AT&T’s Cingular has a network-based 911 system, which tends to have a harder time in rural areas.
Spokesman Mark Siegel says there is “no blanket answer” to the question of how Cingular’s 911 system performs in rural areas.
Network-based systems need a minimum of three cell towers to “triangulate” information to figure out the location of a caller. The problem: In some of Cingular’s rural markets, Siegel says, one tower may cover a 1- to 5-mile radius.
How many cell towers, on average, does Cingular have in its most rural markets? He says, “There are fewer towers where there are fewer people.”
No matter where cell users are when calling 911, Siegel says, it’s a good idea to “be prepared to give the dispatcher a reasonably good description of your surroundings.”
Most important, he says, customers should have realistic expectations whenever they dial 911 using a cellphone. “It can never be as precise as a land line.”