Your Phone Knows Where You Are

Illustration by Tavis Coburn Illustration by Tavis Coburn

In February 2001, while driving on the state turnpike to her home in Miramar, Florida, 32-year-old Karla Gutierrez lost control of her BMW 328i and skidded into a canal. She dialed 911 on a cellphone and explained her predicament as the vehicle slowly sank. But since Gutierrez couldn't describe her precise location-"I'm not sure where I am," she told the operator-Miami-Dade County rescue units didn't know where to go to save her. By the time a passing patrolman noticed a busted fence by the accident site and found Gutierrez, she was dead.


Cases like this give emergency workers the shivers. If Gutierrez had called 911 from her home, the dispatcher would have instantly seen her exact location on a computer terminal, because landlines are matched to household addresses in emergency-services databases. But mobile phones are untethered to any network and provide no clue about where an SOS is coming from.


With more than 200,000 emergency calls coming from cellphones daily, the Federal Communications Commission is eager to remedy this defect. In 1997, the agency ordered wireless carriers to equip their systems with Enhanced 911 (E911) technologies, which would enable rescuers to pinpoint a caller's location to within a few dozen meters. But privacy advocates aren't convinced that the upgrade, due to be completed by 2006, is good news. They fear E911 could make it impossible for people to do anything without someone-employers and the police, for starters-being able to discover where they are.


There are two competing E911 systems. Most big carriers, like Nextel and SprintPCS, are piggybacking on the Global Positioning System (GPS), a series of 24 satellites originally launched by the Pentagon to aid military operations. GPS chips embedded in new phones factor the arrival time of several satellite signals to compute the caller's longitude and latitude. The downside of the GPS-based approach, however, is that it requires people to buy new phones. Thus carriers such as Verizon Wireless are deploying a different E911 system that works with virtually any existing handset. These carriers are placing sensors inside the towers where mobile signals are routed. When a call for help is sounded, the three or four closest phone towers measure how long it takes for the signal to arrive, then triangulate the victim's coordinates. These systems are being installed in places with relatively low population density, such as Gary, Indiana, and St. Clair County, Illinois. The approach is not as accurate as GPS-based E911, but because distressed callers are usually more visible in a rural landscape, precision is less vital.