USA cell phone callers expect that when we call 911 for an emergency, first responders can find us, even if we can’t tell them where we are.
Don’t count on it.
For example, 911 call centers receive accurate locations for only 19% of California 911 calls made from T-Mobile cell phones.
The causes are complex, and solutions are expensive. Below I provide a simplified explanation.
Bottom line: Today, your 911 call probably will not include an accurate location. And this problem won’t be fixed soon.
Background
The FCC requires cell phone companies to provide 911 call centers with caller locations accurate to 50 to 300 meters (“Phase II locations”) – outdoors – unless you are in certain counties chosen by the cell phone companies.
Several technologies can provide sufficiently accurate locations, including GPS built into the phone, cell tower triangulation, and a few complex methods using cell towers or TV stations.
If the cell phone company can’t provide an accurate location, they provide a “Phase I” location, i.e. the location of the cell tower handling your call. Since some cell towers cover over 100 square miles, these locations are not very useful for 911 call centers.
In order to provide accurate 911 call locations, most cell phone systems require cell phones to send GPS locations, so every new cell phone includes a GPS receiver.
Problem
Since 2008, the percentage of cell phone 911 calls with accurate locations has dropped or barely changed for most cell phone systems. Here’s a chart from five areas in California; similar problems have been reported in other states.

In particular, accurate locations for calls from AT&T and T-Mobile phones have dropped significantly and continue to decline. Only Verizon provides accurate locations for just over half of 911 calls; other companies are worse.
The causes are complex, and each side in the argument makes certain claims and refutes claims from the other side.
In brief, some causes might be:
– Over-reliance on GPS. GPS positions are not available inside buildings (where an increasing percentage of 911 calls are made), and 911 positions are not immediately available to 911 call centers (due to the time required to generate a GPS position).
– 911 call centers don’t “re-bid” (ask again 30 seconds later) for location information. Cell phone companies claim that 99% of 911 calls contain accurate information, eventually. However, many 911 calls don’t last long enough for a re-bid, and some 911 call centers can’t or won’t re-bid.
– The FCC permits cell phone companies to exclude counties, or portions of counties, only where wireless carriers determine that providing location accuracy is limited, or technologically impossible, because of either heavy forestation or the inability to triangulate a caller’s location. After 30 minutes of digging, I could not find those reports for Verizon, AT&T, or Sprint; I’ve linked to T-Mobile’s exclusion report below.
Solutions
Today, November 18, 2013, the FCC, 911 call center representatives, and cell phone company representatives are in a workshop to try to fix the problem. Expect a lot of finger-pointing and no real solutions, since probably everybody involved needs to spend more money to solve the problem: adding better location technologies, upgrading 911 call centers, etc.
Bottom line
Today, your 911 call probably will not include an accurate location. And this problem won’t be fixed soon.
References
FCC 911 Wireless Services
http://www.fcc.gov/guides/wireless-911-services
FCC Workshop On E911 Phase II Location Accuracy, November 18, 2013
http://www.fcc.gov/events/workshop-e911-phase-ii-location-accuracy
Wikipedia has a good overview of different 911 location technologies:
http://en.wikipedia.org/wiki/Enhanced_9-1-1#Wireless_enhanced_911
News reports on 911 location problems:
http://www.latimes.com/local/lanow/la-me-ln-911-caller-location-20130812,0,5926945.story
http://www.gsnmagazine.com/node/38866
http://www.insidegnss.com/node/3780
AT&T’s public response to these problems:
http://www.attpublicpolicy.com/public-safety/making-911-calls-in-california-2/
T-Mobile list of excluded counties:
http://apps.fcc.gov/ecfs/document/view?id=7021747627


