Chip NoVaMac said:
Thanks for giving us a "first responders" view on the matter. OT of sorts. I know you are in Canada, but I assume that the 911 systems there are not much different then the US. What about the landline vs. wireless as a persons primary phone. I know there is something called E911 for wireless. What can you say about the move towards wireless phones as the primary and only phone line and 911 response?
Good questions. Yes I am in Canada however the 911 landline system is standardized throughout North America. The 911 system for wireless carriers is still in a bit of a flux everywhere, however.
E911 stands for Enhanced 911, and virtually all of North America currently has E911 for
landline phones. Prior to E911, like 30 years, ago calling 911 would only result in the caller's number being displayed on the calltaker's screen. This
Automatic Number Index, or ANI, was nothing more than we get with basic Call Display at home now, but it was a huge step forward for public safety as it allowed the emergency services operators to phone the caller back if the line was disconnected. If there was cause for concern, the calltaker could also "manually" check with the phone company records and find out to whom and where that phone number belonged.
E911 added two big features to basic 911 service --
CPC or Calling Party Control, as well as ALI or Automatic Location Index. CPC essentially allows the 911 calltaker to "take over" the phone line of that calls in and they keep control until they decide to release the line. That means that you can call 911 and hang-up (or rip the phone out of the wall and beat your wife over the head with it) but your line will remain "open" and locked to 911. If you try to pick up the phone again, all you will hear is the 911 operator. CPC also allows the 911 operator to do priority ringbacks -- even to pay phones that don't normally ever ring. In other words, when I answer a 911 call, your phone line belongs to me until I'm convinced you can have it back again!
ALI is part of the E911 data packet that instantly sends the 911 calltaker the caller's name and address as it is printed in the phone book. This is clearly a lifesaver as it quickly and easily pinpoints the caller -- as well as allows downstream dispatch agencies to look-up previous dealings with the people at that address. Not only things like medical problems, but also responder safety issues such as previous domestics, weapons calls, or even attack dogs or hazardous chemicals at the location.
But to (finally) answer your question -- there is still no easy way to locate cell phones that call 911. Currently all most agencies get from cellular 911 calls is the number of the cell phone, as well as the location of the tower that picked-up the call. But as even de-activated cell phones can still call 911 (most people don't know that....) the calltakers are not able to ring back de-activated phones, which is very frustrating. Also, many people now consider cell phones to be disposable items -- especially now that it's much cheaper to buy a new phone than to replace the batteries.
Several different methods are being tested for locating cell phone 911 calls including Bearing, Triangulation and GPS. Bearing methods work well in flat rural areas, where the tower receiving the cellular call knows the angle the signal is coming in from, as well as the relative strength of the signal. Do the math, solve a few equations, and you can make an educated guess that this call is being placed 15-to-17 miles from the tower in a north-north-westerly direction. (Not great, but better than nothing...) Triangulation methods work well in built-up areas where one cell call can be picked-up on multiple towers at different signal strengths. The towers mathematically figure-out where a cell phone has to be in order to provide the relative signal strength to each tower. That gives a fairly wide search area and it is of limited use when the cell phone is moving (and they often are!). The benefit is, both Bearing and Triangulation techniques are tower-based and work with all existing cell phones, digital or analogue. I understand some large cities have already implemented such features for tracking all 911 cell calls. However the GPS-based system is much better, but it obviously requires special GPS-enabled digital cell phones and substantial upgrades to every part of the chain. GPS-based phone locations are very accurate and can be tracked when moving.
(This is a lot like the current OnStar technology -- I love getting calls from OnStar -- they'll tell you there's been an airbag activation 4.7-miles west of Springfield on Route 3, you're looking for a red Envoy, and it's probably down in a ditch because it is 12' below grade level... amazing!)
I think by the end of this year we will have an adopted standard for E911 cell phone ALI, but I'm not sure of the timetable for national implementation. A third of all 911 calls we answer at work are cell phone calls, but most of those are accidental mis-dials (de-program your 911 speed dial buttons!!!) But what really scares the hell out of us are the VOIP systems that currently don't conform to any standards -- you want a New York number in Detroit? Fine, here ya go... you're in New York City now!
Technology marches on.... society just tries to keep up!