Before the age of mobile phones, when a 911 call came in, figuring out its origin point was straightforward. A cry for help coming via a landline had to be from a static location, by definition. After all, someone’s house wouldn’t be driving down the highway or hiking in a park. But the majority of adults—68 percent, according to 2021 data from the National Center for Health Statistics—reside in homes that lack landlines. And most 911 calls, unsurprisingly, come from cell phones.
Detecting a cellphone’s location during a 911 call is more complex than when it comes from a landline, but last week, AT&T announced that they were set to boost the specificity of their location-detection tech for mobile phones considerably. Here’s how it works now, how it’s changing, and how it stacks up against the competition.
From landlines to cell phones
Determining a location that’s coming in via a landline is “easy,” says Chris Sambar, an executive vice president at AT&T Network. “A landline’s registered at a specific address.” The call coming in “gives location information.”
With a cell phone, the location information is traditionally detected based on the towers relaying the signal to AT&T. “We use the cell towers to get the location of the caller,” Sambar says. That can provide location information that’s as large as a 10-mile radius, he says. “Sometimes it’s hard to pinpoint where the caller is,” he adds.
Behind the scenes, an imprecise location can cause delays, and that’s due to the fact that the correct public-safety answering point (the industry calls this a PSAP) needs to handle the call. Imagine you make a call from the edge of a state or county, and a cell site from the other region picks it up—your call could be routed to a dispatcher at a PSAP in a different region. Then, the authorities need to transfer the call to the right place. This new, more precise method should help mitigate that problem.
It works, Sambar says, thanks to considering more information than just cell towers for people on the AT&T network. “We now have more data from the device, using a combination of GPS, wifi, [atmospheric] pressure sensor in the device, [and] accelerometer in the device,” he says. The result is that the location accuracy is boosted: the system can now locate the caller within about 164 feet, AT&T says.
That helps get the call to the right PSAP, and it also gives the dispatcher better location info, according to AT&T and Intrado, a company that focuses on 911-related technology.
In terms of privacy, AT&T says that the detailed location tracking only occurs during an emergency call. “This can only happen while a 911 call is initiated and in progress,” says Adan Pope, the chief technology officer with Intrado. “Not before and not after.” (As the Verge points out, concerns about location tracking, bounty hunters, and data from the carriers were raised by a 2019 Motherboard investigation.)
What are other carriers up to?
The news that AT&T and Intrado are boasting about is that they are the first group in the US to deploy such a service with this level of accuracy at a large scale. “The nationwide rollout is scheduled to be completed by the end of June,” AT&T said in a press release, noting that it was already working in 16 states and Guam.
“This technology is irrespective of the local public safety answering point’s technology sophistication,” says Nate Brogan, a senior vice president with Intrado. “So we’re not dependent on any local infrastructure or any other advanced technologies that may have already been deployed in those regions to accommodate it.”
Here’s where things get a little more nuanced. AT&T competitor T-Mobile said in late 2020 that it was rolling out location-based routing—using a person’s location to get their call sent to the best PSAP—“in parts of Texas and Washington State,” the company said in a press release.
That list has grown since then. In an email, a T-Mobile spokesperson said: “We offer the [location-based routing] capability nationwide and are working with PSAPs across the country to implement it.” Currently, they have it in the following places: Washington, DC, Florida, Georgia, Iowa, Illinois, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnisota, Missouri, Ohio, Oregon, Tennessee, Texas, Utah, Virginia, and Washington. (Just because a state is on the list doesn’t mean the updated location service is engaged across the entire state.)
The same spokesperson added in a phone call that they work with PSAPs as they begin to offer the new service, and that their location accuracy is also within the same 164-foot standard; he also said that like the AT&T system, no technological upgrades are required.
Verizon did not respond to a request for comment from Popular Science.