911 on Fido

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JF Mezei - 26 Aug 2005 20:34 GMT

Called Fido for a long standing question I had.

If you call 911, all they get is your phone number. It seems the 911
agency and/or Police must then call Fido to get your address/name etc.

However, they are supposedly capable of triangulating your position
assuming enough antennas see you. But for this to happen, you must stay
connected to the 911 service long enough.

So in case of an emergency, you should expect to have to provide your
information , even if you're at home, and do not disconnect from the
call in order to give them a chance to triangulate your position.

In remote areas where you're seen by only one antenna, they can only get
your distance from antenna, so if you're 20km from antenna, it is a big
area :-)

Can anyone confirm the above ?

Seems interesting that the government would be so keen on forcing VoIP
providers to provide full 911 service while the mobile phones wouldn't
even be required to provide the onwer's basic info.

BTW, in the USA, the FCC required all VoIP providers to have all their
customers sign a waiver where they acknowledge that 911 service is not
up to par, those who have not signed the form by the end of the month
will have their service pulled entirely. Article I read stated that
about 80% of subscribers had signed it, but that leaves still about
100,000 people who might see their VoIP service cut by end of month.

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DevilsPGD - 27 Aug 2005 07:26 GMT

>Called Fido for a long standing question I had.
>
[quoted text clipped - 18 lines]
>providers to provide full 911 service while the mobile phones wouldn't
>even be required to provide the onwer's basic info.

The majority of calls to 911 from mobile phones are not from the
caller's home, which means the address (if provided to the 911 operator)
would be misleading at best, and would potentially result in emergency
services being dispatched to the wrong location.

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A cheap shot is a terrible thing to waste.

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JF Mezei - 27 Aug 2005 08:15 GMT

> The majority of calls to 911 from mobile phones are not from the
> caller's home, which means the address (if provided to the 911 operator)
> would be misleading at best, and would potentially result in emergency
> services being dispatched to the wrong location.

But at least the 911 folks would have a home contact information. And if
in an amergency at home, you could just say "I am at home, there is a
fire/someone dying etc.

So the thing to remember is that you are expected to provide your exact
location, and if you are unable to provide location, you must leave your
call to 911 opened so thay can triangulate your position even after
you've lost consciousness etc.

In a real emergency, you often don't have much time to think. So
drilling in your head that 911 on a mobile isn't as "complete" as 911 on
landline reduces the thiking requirement when there is an emergency.

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DK - 29 Aug 2005 00:16 GMT

I can confirm that.

You are correct, they are capable of triangulating with at least 2 towers,
and more accurately if more are present by taking the average of each
reading.

There is a service on the CDMA networks called E911 ( $0.50/month), where
more and more new phones come with an AGPS receiver in each phone that would
help save time in triangulation and just transmit the coordinates in a much
shorter time.

The Difference between GPS and AGPS is:
-In AGPS, the receiver in the phone only listens to the data stream sent
by the NAVSTAR satellites and sends the stream to the cell towers where the
calculations are done there. On top of that, the tower uses itself as a
reference for an even more accurate position, it can come down to a radius
of 1m
-In GPS, the receiver listens and calculates the position, its accuracy
varies up to a maximum error of 100m, which is still not bad.

> Called Fido for a long standing question I had.
>
[quoted text clipped - 14 lines]
>
> Can anyone confirm the above ?

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JF Mezei - 29 Aug 2005 01:24 GMT

> There is a service on the CDMA networks called E911 ( $0.50/month), where
> more and more new phones come with an AGPS receiver in each phone that would
> help save time in triangulation and just transmit the coordinates in a much
> shorter time.

Does anyone have some statistics on what percentage of 911 calls are
made from locations where the handset has line of sight with enough
satellites to trinagulate ? GPS signals are very very sensitive to
things like dense forest, walls, ceilings etc.

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G M - 31 Aug 2005 05:50 GMT

>> There is a service on the CDMA networks called E911 ( $0.50/month), where
>> more and more new phones come with an AGPS receiver in each phone that
[quoted text clipped - 7 lines]
> satellites to trinagulate ? GPS signals are very very sensitive to
> things like dense forest, walls, ceilings etc.

When I used the "Map Me" application on my previous phone with Bell Mobility
inside my house, it pegged me at one house over which is pretty accurate for
not having line of sight. When I was outside, the accuracy was much higher,
to the point of being able to say that the claims of 100m accuracy could
very well be a high estimate to protect themselves.

I was quite impressed with the service, although I really don't see much
point in it. Sure it could give you directions to the nearest gas station,
but so could anyone on the street.

I don't think that it relies entirely on GPS satellites, I think it uses
cellular tower triangulation as well.

Gregg

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