Your smartphone knows your location well enough to send a car to where you're standing in a busy city, map a morning run through the woods, or navigate inside an airport.

But if you call 911 from that same mobile phone, emergency responders will only have a vague sense of where to send an ambulance, fire truck, or police car.

The difference in distances can be the difference between life and death.

Apple is rolling out a new feature in its next iPhone software update to send emergency responders instant, precise location information in the US. The update, coming in iOS 12 later this year, calculates a caller's location based on data collected from WiFi access points, nearby cellular towers, and GPS.

The tricky part isn't finding out where a caller is — Apple has been using its hybrid location technology since 2015 — but relaying that information to a fragmented and aging 911 system built for landlines.

Of the 240 million calls made to 911 each year, more than 80% are from mobile devices, according to NEMA.

Apple is working with a startup called RapidSOS, which specializes in sharing a cell phone's location information to the major programs used by the 6,300 emergency response departments across the US. RapidSOS offers its integration as a free software update to existing 911 dispatch systems.

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The companies announced the feature Monday at the National Emergency Number Association (NEMA) conference in Nashville.

"The 911 system is literally 50 years old this year. It has not made the evolution into the digital era," said former FCC chairman Tom Wheeler, who is an investor in RapidSOS.

Wheeler has been pushing for more accurate 911 location information since he was at the FCC, but only invested in RapidSOS after he left in 2017. Two other former FCC chairmen, Dennis Patrick and Julius Genachowski, are also investors.

Not all callers in an emergency know where they are, and some cannot verbally communicate their location. They might be in medical distress, or unable to speak because it would put them in danger. In those cases, calls from mobile numbers have to be located using cell tower information from carriers, which can result in a radius of hundreds of yards.

Getting medical attention in the first 60-minutes after a traumatic injury is key to preventing death. Emergency professionals call this window the "golden hour." In a 2014 report, the FCC estimated inadequate location information leads to more than 10,000 unnecessary deaths a year.

Over the past five years, RapidSOS has visited thousands of public safety agencies around the country, said founder and CEO Michael Martin. The challenge was finding the ways to work with all of those systems without slowing down responses or overloading dispatchers with information.

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Now when a 911 center receives a call from a device using RapidSOS's technology, the dispatcher's software asks the RapidSOS database for more data. In addition to location data, RapidSOS might have other data like a person's medical records.

The company recently announced a partnership with Uber, which adds a button for calling 911 inside of the ride-hailing app. Google did a pilot program with RapidSOS recently, but does not currently include the option in Android.

Apple says it will not provide the name of the caller and will only share the location information in an emergency, for privacy reasons. The feature can't be accessed for non-emergency calls. It will be turned on by default for all iOS 12 iPhone users in the US, but Apple says it will add an opt-out option in settings.

This isn't Apple's first emergency feature. Earlier this year, it added Advance Mobile Location (AML) to iOS, another standard for sharing a caller's location with emergency services. AML is not currently supported in the US, and only works in nine countries.

Google also has its own version of the technology, called Android Emergency Location Services (ELS), available on more recent Android phones. It works in 14 countries, but not in the US yet. The company says it is working toward launching a similar service in the US.

iPhones also have an emergency SOS feature, which automatically calls emergency services and texts any emergency contacts your location.