March 31, 2021
The Wireless Industry’s Commitment to 9-1-1 Location Accuracy .
Demetria was on a nature walk in LA when she suddenly felt a warm sensation come over her, followed shortly by the feeling of her throat closing up. She immediately dialed 9-1-1 on her cellphone, and as her voice started to leave her, managed to relay her condition to the 9-1-1 operator. What she didn’t have time to share was her location. Yet, when she woke up, she was safely in the hospital, recovering from a severe anaphylactic reaction.
Demetria is one of millions of Americans whose cellphone helped save their life. Today, 9-1-1 operators can locate you nearly anywhere—from the side of a highway to inside your home—all thanks to decades of innovation in wireless location accuracy technologies.
These innovations are what enables a wireless provider to give a 9-1-1 operating center, called a Public Safety Answering Point (PSAP), an estimated location for a 9-1-1 caller. The 9-1-1 operator then combines the wireless caller’s estimated location with their own mapping software (GIS) to send a first responder, like police, fire, or EMS, to help.
We love the mobility and freedom that our wireless devices enable, allowing us to communicate from virtually anywhere. That mobility means finding a 9-1-1 caller can be challenging. Despite those challenges, the wireless industry has worked tirelessly for many years to make sure 9-1-1 operators and first responders can find you quickly.
Always Improving 9-1-1 Location Accuracy.
Enhancing wireless 9-1-1 location accuracy began with the use of network-based location techniques to estimate the location of a caller. When you place a 9-1-1 call, your phone pings the nearest cell tower, and this information can be used to triangulate between cell sites to come up with an estimated location, which is shared with the 9-1-1 operator.
The first iteration of network-based triangulation relied on calculating the angles of your position between two cell sites to determine a location which was then shared with the 9-1-1 operator.
Wireless: A Critical Lifeline | Solving Location Accuracy
As technology advanced, the industry moved to a variety of different triangulation techniques, including time difference of arrival (TDOA) techniques, which determined the time difference from when your phone call “arrived” at one cell site compared to the arrival time at a second cell site, allowing for a calculation of your distance from and between the two sites.
The other key innovation for location accuracy was the ability of mobile device manufacturers to add Global Positioning System (GPS) receivers into their handsets. If the phones can “see” multiple GPS satellites, this feature can provide a very precise location and augment the network-based triangulation estimate. Today, virtually all smartphones and feature phones in the United States are equipped with GPS receivers.
These improvements transformed the industry’s ability to provide reliable latitude and longitude location data, particularly for outdoor locations. Today, more than 80% of wireless callers to 9-1-1 are located within 50 meters, which makes it easier for first responders to find the caller quickly.
Real Progress on Indoor Location.
As consumers have increasingly adopted cellphones as their only phone, wireless 9-1-1 calls are now not just being made outdoors, but also indoors. Along with this shift in use, the wireless ecosystem has addressed challenges in locating 9-1-1 callers inside buildings, where construction materials can block wireless and GPS signals.
In 2014, public safety officials and policymakers encouraged the industry to adopt new solutions to address indoor accuracy, both in the horizontal and vertical dimensions. With innovation and expertise from some of the top engineers, the industry worked quickly to develop state-of-the-art device-based hybrid (DBH) technologies, which were tested starting in 2015 and have now been deployed. This new tool has been a game changer for locating in-building callers, in particular.
Device-based hybrid solutions use a combination of technologies and sensors—including satellite GPS and crowd-sourced Wi-Fi measurements—along with wireless providers’ other 9-1-1 network and device information, to produce a higher-accuracy location. This is the same technology used to call a car on a ridesharing app or use a navigation app. The device providers launched these capabilities within software updates to existing devices, leveraging the technological capabilities of recent models.
Over 99% of active Android devices can leverage a device-based hybrid solution called Emergency Location Service (ELS) to provide a more accurate location using a variety of sensors in the device. Available on the vast majority of Apple phones, the device-based hybrid solution is called Hybridized Emergency Location (HELO). HELO fuses information from a variety of sensors in the device, including Global Navigation Satellite Systems and Wi-Fi along with network-provided assistance data, as appropriate, to provide an estimate of the 9-1-1 caller’s location.
Operators serving 99% of consumers are leveraging device-based hybrid technologies to locate callers inside buildings with increasing accuracy.
Solving the Vertical Location Challenge.
With horizontal location being improved dramatically, including indoors, the next challenge the wireless industry is working on is locating 9-1-1 caller’s vertical direction, which is especially important if the caller is in a multi-story building.
Device-based hybrid technologies also help in this regard, providing estimated location information in the form of a latitude, longitude—and increasingly, height—to the 9-1-1 operator.
The newest innovations in the vertical location accuracy arsenal are barometric pressure sensors. Found in the latest smartphones, their precise measurements may enable even more accurate height estimates, which when combined with device-based hybrid solutions and any information the 9-1-1 operator has about the building are especially helpful for locating 9-1-1 callers who could be on any floor.
While 9-1-1 call centers continue to develop their technology to accept vertical locations, providing a height estimate can help 9-1-1 call centers dispatch first responders more accurately, who in turn can respond to a caller in need quickly. To continue to improve these vertical estimates, the industry is examining new and innovative ways to leverage sensors, software advances, and cutting-edge technologies.
With around 80% of approximately 240 million 9-1-1 calls made via wireless, the industry knows what an important lifeline your mobile phone is in an emergency. This knowledge fuels our ongoing research and development into location accuracy technologies and advocacy around making location estimates even more accurate. With our public safety partners, CTIA and our member companies are—and will remain—committed to constantly improving our nation’s 9-1-1 system so help can find you as quickly and accurately as possible.