Public-safety answering points (PSAPs) should be able to get much more accurate location data from 911 callers using wireless devices indoors by leveraging information provided by commercial infrastructure such as small cells, Wi-Fi systems and Bluetooth beacons, officials for the National Emergency Number Association (NENA) said in describing the details of the recent agreement struck with the four nationwide U.S. wireless carriers.

Much of the attention focused on the agreement has centered on the notion of carriers delivering a “dispatchable address” for each 911 call using a wide variety of commercial infrastructure instead of just relying on satellite GPS and network-based triangulation to determine XY coordinates that can be translated into a physical address for first responders.

“Certainly, we believe that this is new thinking, if you will, with respect to looking at 911 location, because it now moves to a specific address and a specific location that is better than metrics of meters,” NENA CEO Brian Fontes said during an interview with IWCE’s Urgent Communications. “Nonetheless, there will still be improvement in location, short of the dispatchable address.”

With this in mind, the satellite XY coordinates are expected to become more accurate by utilizing Global Navigation Satellite System (GNSS) infrastructure other than the U.S.-owned Global Positioning System (GPS). By augmenting GPS readings with readings from the GLONASS satellite constellation from Russia—other satellite systems can be leveraged as they come online—the XY coordinates provided by satellite technology should be much more accurate than they are today, according to Trey Forgety, NENA’s director of government affairs.

But leveraging additional satellite infrastructure does not change the reality that satellite location technology always will have limited value when a 911 call is made from inside a building, because the building structure typically blocks the satellites’ view of the 911 caller. A similar problem arises with network-based triangulation approaches using macro cell towers.

With this in mind, the agreement between NENA, the Association of Public-Safety Communications Officials (APCO) and the four nationwide wireless carriers in the U.S.—AT&T, Verizon, Sprint and T-Mobile—calls for leveraging location information from distributed antenna systems (DAS), small cells, Wi-Fi access points and Bluetooth beacons that are becoming increasingly prevalent in today’s indoor environments.

When a 911 call is made from a wireless device, the device will note the media access control (MAC) address of surrounding infrastructure with known physical locations, which are used to determine the caller’s location, according to Forgety. Given the proliferation of various indoor-communications infrastructure to meet consumers’ insatiable demand for high-speed connectivity, the number of location data points for indoor 911 calls should increase rapidly, which should yield greater location accuracy.

 “What we’re going to see over time is a dramatic expansion in the fraction of calls that are able to deliver that [dispatchable address] in addition to an XY coordinate,” Forgety said during an interview with IWCE’s Urgent Communications.

Today, the most automated approach to determine the location of a wireless 911 is called reverse geo-coding, which is a process that attempts matches the XY coordinates with a particular address found in a GIS database—a private one owned by a county, or a public one owned by someone like Google, Forgety said. Unfortunately, this process typically does not yield accurate location data, he said.

Intrado did a study of this, and more than three quarters of the time, that process yields the wrong address,” Forgety said. “In fact, 85% of the time it was wrong in urban environments. That gives you an idea of the state of the art. The other thing that is done is even less precise than that. The call-taker can look at the dot on the map and say, ‘That’s sort of close to 123 Main Street.’

“[By leveraging the dispatchable location of known wireless infrastructure,] this moves us to a future where those error-prone processes are taken out of the equation.”