Industry Disagrees on Best 9-1-1 Indoor Location Data Delivery Option
Monday, June 03, 2019 | Comments

There is widespread disagreement among public-safety groups and industry on the best way to deliver indoor wireless location data for 9-1-1 calls to dispatch centers from wireless providers based on comments filed with the FCC.

In March, the FCC sided with public safety and proposed a vertical (Z axis) location accuracy metric of ±3 meters relative to the handset for 80 percent of indoor wireless 9-1-1 calls. The new rules would help first responders more accurately locate people who make wireless 9-1-1 calls from multistory buildings, said the commission, which requested comment on the proposal.

The majority of those who submitted comments agreed that a location accuracy metric of ±3 meters relative to the handset for 80 percent of indoor wireless 9-1-1 calls is attainable, but the disagreement surrounds how to deliver that information to public-safety answering points (PSAP).

The Association of Public-Safety Communications Officials (APCO) comments suggested a dispatchable location including the room number, floor, street and city where a 9-1-1 call originated is the best option for location accuracy.

“The benefit of the dispatchable location is that it provides location information that would be easy for first responders to react to,” said Walt Magnussen, PhD, Texas A&M Internet2 Technology Evaluation Center (ITEC) director. “It would include the z-axis in the form of a floor level, which if accurate and coupled with a room number, would allow the first responder to quickly get to the scene. The problem with this format is that there are no standards in a dispatchable location for the floor number or level. In a multistory building such as a hotel that has a sublevel or basement, then a ground floor or lobby, then is the first floor the second floor, the second level or the fourth level? Then we add complications like the 80% of the buildings that do not have a 13th floor.”

In its comments, the National Emergency Number Association (NENA) requested a geodetic location, which is latitude, longitude and elevation. A geodetic location is based on the industry-approved Presence Information Data Format Location Object (PIDF-LO) standard defined in Internet Engineering Task Force (IETF) RFC 4119, which was initially drafted in December of 2005 and has been updated three times since.

NENA made four points in its comments. Dispatchable location, as defined, is not the most accurate, useful or efficient means to locate an individual. Geodetic location information provides the best information for 9-1-1 to locate a caller. The location of a caller must be delivered to the 9-1-1 system as a standards-based, interoperable LO, carried over IP and expressed as a geodetic LO, which includes the FCC’s proposed z-axis measurement. CTIA’s most recent report calls into question the future viability of the National Emergency Address Database (NEAD), NENA said.

The May 20 deadline for comments followed a CTIA report that found only 38.7% of valid test calls conducted during recent dispatchable location testing for 9-1-1 calls produced a result that meets the requirements for actionable dispatchable location as defined by Alliance for Telecommunications Industry Solutions (ATIS) standards.

For Eddie Reyes, director of the Office of Public Safety Communications in Prince William County, Virginia, knowing the door to knock down during an emergency is critical. "To me, the dispatchable location — the civic address generated through the NEAD — is what we’re looking for," Reyes said.

In its comments, ATIS said that to ensure that PSAPs can convert location information to the format that best suits their needs, a baseline requirement would be to deliver the information as height above ellipsoid per World Geodetic System 1984 (WGS-84) datum. T-Mobile also advocated for the FCC to adopt WGS-84 as the reference system for altitude estimates instead of floor identifiers.

AT&T said carriers should be required to provide z-axis location information only as height above mean sea level (MSL) rather than height above ground level (AGL) or a specific floor level. MSL provides the most reliable method for measuring compliance as it does not vary by building characteristics or unique geography like AGL, AT&T said.

“Indeed, converting MSL data to AGL data requires familiarity with variations in terrain and specific structure characteristics,” the AT&T comments said. “First responders are more familiar with the terrain and structures in their jurisdictions and are in the best position to use the z-axis data to identify emergency caller location in a given structure. Thus, to minimize the risk of error, it is appropriate that carriers provide MSL data that first responders can use to precisely locate emergency callers.”

The Boulder Regional Emergency Telephone Service Authority (BRETSA) said it prefers vertical location information be presented as a height AGL and MSL, with accuracy and confidence data.

Location technology vendor NextNav said to ensure technical neutrality, the commission should refrain from adopting any measurement standard to report vertical location information. If a standard is adopted, however, it should be height above ellipsoid (HAE), which NextNav said is the most accurate and reliable means available and is also the standard used for the GPS. “Other options, such as height above MSL, height AGL or the floor number assigned by the building owner, would introduce additional variables in the calculation process, some of which would be impossible to achieve using existing technology and would inevitably reduce reliability and cause confusion for public safety,” the company said in its comments.

The International Association of Fire Chiefs (IAFC), National Association of EMS Officials (NASEMSO) and the National Sheriffs’ Association (NSA) submitted joint comments noting the FCC should direct wireless carriers to focus additional efforts on achieving compliance with the dispatchable location requirement and on developing the NEAD database further to ensure that a dispatchable location is achieved, with significant yield.

Magnussen said using the power of smartphones’ current and future location acquisition mechanisms to calculate the most accurate x, y and z location makes sense. “It is uncertain how either the device or a service provider supporting the device would use this information to generate the floor and room number for mobile callers,” he said. “Any such system would further tie us to static databases such as the current ALI (automatic location identification) databases, which is counter to all next-generation 9-1-1 (NG 9-1-1) initiatives.”

A link to all the comments is here. Reply comments are due June 18.

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