Another reason to carry

[Andrew17019]

Interesting link on CNN today,

http://www.cnn.com/2010/TECH/mobile/...ex.html?hpt=C2

From a cell phone it's taking even longer for emergency responses to figure out where you are when placing a 911 call. This further reinforces the fact that a 911 call by itself is not sufficient for your personal safety, and that you really do need to have your own personal security when seconds can be the difference between life and death. You can't just rely on your new iPhone to save your life in an emergency!

[knight0334]

As a communications engineer, I can tell you 911 calls from a cell phone are worthless unless you as the caller can give a detailed description of the location so that they can find you. Landlines are tied to a fixed service address, cell phones are tied to your billing address - which you can be on the other side of the planet using it. Then it takes time to access and GPS coordinates(if the phone can beacon 3 birds), or to triangulate with 3 cell towers.

So, if you're in a wreck and rely on a cell phone, and cannot give directions - you're F'd.

[PennsyPlinker]

As a communications engineer, I can tell you 911 calls from a cell phone are worthless unless you as the caller can give a detailed description of the location so that they can find you. Landlines are tied to a fixed service address, cell phones are tied to your billing address - which you can be on the other side of the planet using it. Then it takes time to access and GPS coordinates(if the phone can beacon 3 birds), or to triangulate with 3 cell towers.

So, if you're in a wreck and rely on a cell phone, and cannot give directions - you're F'd.

As a person who lives at the boundary of two counties, and who has an address from the town in the other county, and who has had occasion to call 911 a number of times for accidents along our road, I can confidently say that even a detailed description is no good. I have had operators argue with me about what county I am in, question my ability to know where I am, and even told me they have no idea where I am after I give them TWO cross roads within several hundred yards of one another.

And this does not even take into account wasted time because I have to rehearse my story to two operators after the first one makes me give all the details, only to tell me, "We don't cover that area".

[donm]

As a communications engineer, I can tell you 911 calls from a cell phone are worthless unless you as the caller can give a detailed description of the location so that they can find you. Landlines are tied to a fixed service address, cell phones are tied to your billing address - which you can be on the other side of the planet using it. Then it takes time to access and GPS coordinates(if the phone can beacon 3 birds), or to triangulate with 3 cell towers.

So, if you're in a wreck and rely on a cell phone, and cannot give directions - you're F'd.

Well, you're kind of going in the right direction. This article is several years out of date -- obviously one of those "filler" articles that somebody tossed together without doing any research. The vast majority of the country is served by "Phase II" location technologies (it also requires the public safety answering point to have equipment to accept it). As noted, there are two flavors: Assisted GPS (the "assisted" part is important) and Time Difference of Arrival, commonly called triangulation. Each is triggered automatically when a call to an emergency number is placed.

An A-GPS fix typically takes about 15 seconds (BTW, you can't turn this off from any menu). The reason that it's so fast is the "assistance" data that the network passes to the phone. The reason it takes your Garmin minutes to start up after it's been off for a while is that it needs to download (from the satellites themselves) a lot of satellite orbital parameters -- and then starts from scratch. The assistance data gives the phone that info, plus its approximate location, allowing it to make a "fix" much faster that a cold start. But you need to see the sky, and GPS has problems inside buildings (hint: stand near a window if you can) and in "urban canyons" in big cities. This technology is used by CDMA and iDEN carriers including Verizon, Sprint, and Nextel.

GSM carriers, including AT&T and T-Mobile, use a network-based solution that makes timing measurements from multiple cell towers (typically a dozen or more in an urban/suburban area). These locations are typically delivered about five seconds after you press the "send" button. This technology works well in urban/suburban areas but is less accurate out in the sticks where cell towers are far apart.

[Pa. Patriot]

As a communications engineer, I can tell you 911 calls from a cell phone are worthless unless you as the caller can give a detailed description of the location so that they can find you. Landlines are tied to a fixed service address, cell phones are tied to your billing address - which you can be on the other side of the planet using it. Then it takes time to access and GPS coordinates(if the phone can beacon 3 birds), or to triangulate with 3 cell towers.

So, if you're in a wreck and rely on a cell phone, and cannot give directions - you're F'd.

This is not accurate, currently. I'm not up on all the particulars, but the federal mandates for E911 coordinate info are in place pretty much country wide, as far as I know. When placing a call to 911 from a cell, the dispatch center receives coordinate info *with the call*, as processed and sent by the cellular provider.
I've worked with the equipment used here in Pa.

That's not to say the data is always reliable or that the dispatch center handles the info correctly though...

[knight0334]

This is not accurate, currently. I'm not up on all the particulars, but the federal mandates for E911 coordinate info are in place pretty much country wide, as far as I know. When placing a call to 911 from a cell, the dispatch center receives coordinate info *with the call*, as processed and sent by the cellular provider.
I've worked with the equipment used here in Pa.

That's not to say the data is always reliable or that the dispatch center handles the info correctly though...

Mandated they are, but in practice it doesn't work out that way.

As we all know, PA isn't flat and doesn't have total cell tower coverage. You may be able to hit one tower, and you may be able to hit only one bird, all because of geography.

Upon a cell call, the only guarantees that 911 will get is your billing address and the tower in which the call originated. Which can be an area up to 100 square miles which that tower serves. If you dont hit enough birds to get GPS coordinates, or if you cant hit 3 towers - you're pretty much screwed without verbal descriptions.

I can take you to places where you are lucky to hit one cell tower, and you're luck to get 1 satellite with a commercial/utility truck mounted GPS unit. And I can take you to places where you can get locks on neither of the two.


An example is SR 949 in Jefferson Co from Spring Rd to about 3 miles past Clear Creek State Park. You sometimes can get 1 bar to get a call out, and GPS will not hit because you can only hit 1 or 2 birds due to the hills. The operating cell towers are in Brookville and Marienville in which you hit - each about 10 air miles away.

There are also places in Greene, Somerset, Forest, Venango, Elk, and Cambria counties with the same situation.

[Pa. Patriot]

Mandated they are, but in practice it doesn't work out that way.

As we all know, PA isn't flat and doesn't have total cell tower coverage. You may be able to hit one tower, and you may be able to hit only one bird, all because of geography.

Upon a cell call, the only guarantees that 911 will get is your billing address and the tower in which the call originated. Which can be an area up to 100 square miles which that tower serves. If you dont hit enough birds to get GPS coordinates, or if you cant hit 3 towers - you're pretty much screwed without verbal descriptions.

I can take you to places where you are lucky to hit one cell tower, and you're luck to get 1 satellite with a commercial/utility truck mounted GPS unit. And I can take you to places where you can get locks on neither of the two.


An example is SR 949 in Jefferson Co from Spring Rd to about 3 miles past Clear Creek State Park. You sometimes can get 1 bar to get a call out, and GPS will not hit because you can only hit 1 or 2 birds due to the hills. The operating cell towers are in Brookville and Marienville in which you hit - each about 10 air miles away.

There are also places in Greene, Somerset, Forest, Venango, Elk, and Cambria counties with the same situation.

I certainly understand all that. My response was to the assertion that cell phones are "worthless" for 911 coordinates. This is simply untrue in most of the state where cell coverage exists. While the above you posted is true, there are other important facts. Such as even in places where you may only have one serving cell, there is likely other cells that "see" your phone, and can provide e911 data. The signal level needed to take time measurement is far less than the signal needed to exceed the cells pre-set threshold for call coverage. And the data is compiled within seconds of the user pressing send, not minutes.

My point was that even in rural, "spotty" areas, e911 data DOES routinely locate phones within a reasonable proximity. Being on the cell end of many a test of this system I disagree that they are "worthless" in this regard. In some areas, yes, not available. Not the end-all-be-all by any stretch, but quite useful none the less.

[anonymouse]

Do you guys know what the beeping is that you hear every 5-10 seconds while you're on the phone with 911?

[AxiTech]

Mandated they are, but in practice it doesn't work out that way.

As we all know, PA isn't flat and doesn't have total cell tower coverage. You may be able to hit one tower, and you may be able to hit only one bird, all because of geography.

Upon a cell call, the only guarantees that 911 will get is your billing address and the tower in which the call originated. Which can be an area up to 100 square miles which that tower serves. If you dont hit enough birds to get GPS coordinates, or if you cant hit 3 towers - you're pretty much screwed without verbal descriptions.

I can take you to places where you are lucky to hit one cell tower, and you're luck to get 1 satellite with a commercial/utility truck mounted GPS unit. And I can take you to places where you can get locks on neither of the two.


An example is SR 949 in Jefferson Co from Spring Rd to about 3 miles past Clear Creek State Park. You sometimes can get 1 bar to get a call out, and GPS will not hit because you can only hit 1 or 2 birds due to the hills. The operating cell towers are in Brookville and Marienville in which you hit - each about 10 air miles away.

There are also places in Greene, Somerset, Forest, Venango, Elk, and Cambria counties with the same situation.

I remember sitting on my motorcycle, in a driving rain, a couple weeks ago, on top of the hill at Shippensville desperately trying to get one bar so I could make a reservation to a hotel I could have run to in less time than it took to find that one lousy bar!

[donm]

Do you guys know what the beeping is that you hear every 5-10 seconds while you're on the phone with 911?

Probably an indication that you are being recorded.