With multiple rulings from the FCC on wireless 9-1-1 accuracy requirements, knowing what the current rules are and what's coming can be confusing. This page is intended to break down the rules for better understanding. We'll do our best to keep the page up-to-date as new rules are issued. Please let us know if we missed something.
Wireless Enhanced Coverage
Wireless Enhanced 911 Phase I refers to a situation in which 9-1-1 calls from a cell phone to a Public Safety Answering Point (PSAP) is accompanied with Automatic Location Identification (ALI). The ALI display will show the name of the cellular carrier, the carrier's customer service telephone number, the callback number of the caller, and the location of the cell tower delivering the call. In some cases, latitude and longitude may be included with the ALI, but these coordinates denote the location of the cell tower, not the caller.
In Wireless Enhanced 911 Phase II, all of the above is included with the call, but the latitude and longitude displayed will be the location of the caller, not the cell tower. It is important to note that the coordinates displayed are calculated based on either cell tower triangulation or Global Positioning System signal (depending on the cellular carrier), and may not be accurate. Even if a PSAP and cellular carrier are capable of handling Phase II wireless enhanced calls, some wireless calls may still come in as Phase I.
Current 911 Location Accuracy Requirements
Current location accuracy rules apply to 911 calls placed from cellular devices outdoors only. Those rules are:
- All carriers must provide confidence and uncertainty data to the PSAP.
- Carriers using the network-based solution (cell tower triangulation) must deliver Phase II coordinates for callers accurate to within 100 meters 67% of the time for at least 60% of the counties or PSAP service areas they serve and for at least 70% of the population covered. Carriers may "except" up to 40% of the counties or PSAP service areas in their carrier service area.
- Carriers using the handset-based solution (GPS triangulation) must deliver Phase II coordinates for callers accurate to within 50 meters for 67% of calls and 100 meters for 80% of calls for 85% of their call service area. Carriers may "except" up to 15% of the counties or PSAP service areas in their carrier service area.
- All exceptions must be filed with the FCC, the National Emergency Number Association, the Association of Public Safety Communications Officials, and the National Association of State 9-1-1 Administrators.
- Click here for a spreadsheet of current exceptions.
The FCC has approved a time-table set for the implementation of new 9-1-1 location accuracy standards for all cellular calls, including calls made from indoor locations:
- 40% of all wireless 911 calls must be accompanied with a "dispatchable location" (see below) or x/y location within 50 meters (about 150 feet).
- 50% of all wireless 911 calls must be accompanied with a "dispatchable location" (see below) or x/y location within 50 meters (about 150 feet).
- All wireless carriers must deliver barometric (air pressure) data to call centers from any phone that supports that technology
- 70% of all wireless 911 calls must be accompanied with a "dispatchable location" (see below) or x/y location within 50 meters (about 150 feet). Rural, non-nationwide carriers can extend this deadline.
- 80% of all wireless 911 calls must be accompanied with a "dispatchable location" (see below) or x/y location within 50 meters (about 150 feet). Rural, non-nationwide carriers can extend this deadline.
- Nationwide carriers must provide either dispatchable locations or z-axis coordinates in the top 25 cellular market areas.
- Non-nationwide carriers that provide service in any of the top 25 cellular market areas must provide either dispatchable locations or z-axis coordinates in those markets.
- Nationwide carriers must provide either dispatchable locations or z-axis coordinates in the top 50 cellular market areas.
- Non-nationwide carriers that provide service in any of the top 50 cellular market areas must provide either dispatchable locations or z-axis coordinates in those markets.
Dispatchable Location means “the civic address of the calling party plus additional information such as floor, suite, apartment or similar information that may be needed to adequately identify the location of the calling party.”
The Time-to-First-Fix (TTFF) is the amount of time after a call is received by a cell carrier necessary to provide latitude and longitude of the caller (and, eventually, the z-axis coordinate). Under the Feb 2015 rules, the TTFF must be under 30 seconds in order for a call to count toward a carrier's compliance with outdoor accuracy rules.
The confidence factor is the percentage of confidence that a caller is actually within a certain range of the coordinates, and the uncertainty factor is the range, given in meters. For example, if a wireless 911 call is received with a confidence factor of 50 and an uncertainty factor of 200, then there is a 50% chance that the caller is within 200 meters of the coordinates provided.
Under the Feb 2015 rules, all C/U data must be sent with a confidence factor of 90. Meaning that the uncertainty factor will still vary, depending on the quality of the location fix determined by the wireless carrier, but the confidence factor will always be 90. In other words, all uncertainty factors will be a figure, given in meters, and there will be a 90% chance that the caller is within that range of the coordinates provided.
The time frame for making this change to the C/U data isn't made clear in the rules.
Requesting Phase II Service to your 911 Call Center
To begin receiving Phase I or Phase II wireless enhanced calls, the PSAP most notify all carriers in their area that they are capable of receiving them and make a formal request in writing that the carrier begin delivering calls in Phase I or Phase II format. From the date of the request, the carrier has six months to comply.
Visit the FCC's guide for filing complaints.
- How Wireless 9-1-1 Calls Work
- APCO Presentation: Understanding the FCC's New Rules
- FCC - Small Entity Compliance Guide: Wireless E911 Location Accuracy Requirements
- FCC - mobile Satellite Service and 911
Effectiveness and Accuracy of Wireless 9-1-1 Location Technology
There are a number of factors that determine whether a 9-1-1 call center is able to locate a 9-1-1 caller using a cell phone.
- Not every 9-1-1 dispatch center has the required technology to receive location information from wireless carriers delivering 9-1-1 calls to the call center. For more information about the capabilities of Colorado call centers, visit our Wireless 9-1-1 Page.
- Not every wireless carrier is capable of delivering 9-1-1 calls to the call center. Once a 9-1-1 call center is capable of receiving location information with 9-1-1 calls from wireless carriers, they must then make a request to wireless carriers in their area to start delivering location information. Wireless carriers have six months to comply, but they can apply for extensions or waivers.
- Even if location information is delivered by wireless carriers and received by PSAPs, the accuracy of that information can vary widely. New location accuracy requirements put in place by the FCC are complicated and are outlined on our Wireless 9-1-1 Page. The result is that not every cellular 9-1-1 call will be accompanied with enough accuracy to be useful for locating the caller.
- If you have no cell signal, you can’t call 9-1-1 from your cell phone.
Things Affecting the Accuracy of Wireless 9-1-1 Location Technology
Here are some things that affect how accurate location information is when received by a 9-1-1 call center:
- Type of technology used. Wireless carriers may use one of two primary methods for calculating the caller’s location, cell tower triangulation or global positioning system (GPS). Cell tower triangulation is generally less accurate than GPS.
- Local terrain. GPS accuracy is lessened by the presence of tall buildings or anything else that obstructs the line-of-sight between the caller and GPS satellites. GPS and cell tower triangulation are both less accurate if the caller is indoors.
- Availability of cell towers. Carriers using the cell tower triangulation method need callers to have access to at least three cell towers in order to calculate their location. In some rural areas, this greatly reduces the locations where triangulation is possible.
- Status of the phone. The GPS method requires that the phone’s GPS receiver has had time to receive signals from three GPS satellites and calculate the caller’s location based on those signals. If the phone has just been turned on, it can take time for the phone detect GPS signals and calculate its location.
The Future of Wireless 9-1-1 Location Technology
The FCC is currently considering ways to make wireless 9-1-1 location technology more accurate, including the use of hybrid solutions that use both cell tower triangulation and GPS, with one of the focuses of the effort being on improving indoor location accuracy.
Effect of Wireless 9-1-1 on Call Center Call Load
About 80% of 9-1-1 call now come from cell phone, which is not surprising when one considers that over 45% of American households have only wireless phones in the home. Because we carry our cell phones with us everywhere, dialing 9-1-1 by accident is much more common with cell phones than with landline phones. Some areas have estimated the percentage of 9-1-1 calls from cell phones that are accidental to be as high as 40%. This increase in call load with unnecessary calls has increased staffing strains on 9-1-1 call centers and can be a distraction from taking actual emergencies.
Another factor in this increased call load is that it is not always possible to call back cell phone 9-1-1 callers. FCC rules require that wireless carriers deliver 9-1-1 calls from cell phones, regardless of whether that cell phone has a current contract or if it is out of minutes. Cell phones in this status are known as “non-service initialized” (NSI) phones. This also applies to cell phones that have just been turned on and haven’t had time to register on the cell carrier’s network. A call to 9-1-1 from any of these phones is delivered to a local 9-1-1 call center, with our without location information, but without a valid phone number to call the caller back.
Even when a 9-1-1 call from a cell phone is legitimate and the caller stays on the line, it sometimes takes longer to process cell phone calls because of the additional necessity to verify the caller’s location and because the caller may not always be aware of or be able to describe their location to the call taker.
Advancements in Location Accuracy Technologies
As of September, 2018 Apple and Google enabled device location information in IOS 12 release providing faster and more accurate information to help reduce emergency response times.
Android ELS Pilot Report:
TriTech Inform CAD NG911 Clearinghouse Location Testing:
NG911 Clearinghouse Solution Datasheet