911 operators couldn't trace the location [telecom]

911 operators couldn't trace the location of a dying student's phone. > It's a growing issue.

Is it?

I read this piece of YKW* and immediately wondered who her source was, and why she wrote it. It's clearly not in her subject expertise.


The FCC has imposed location requirements on the carriers, and that costs them money. They can not now depend on GPS for several reasons:

a) It does not always work indoors.

b) It does not provide the PSAP with the floor or room.

c) Being a significant power drain, users often have GPS turned off. (Is there anyone out there saying "My phone lasts too long without a charge"?)

d) User may want it off, given the propensity of the carriers to exploit location data for their purposes; i.e. sell users locations to advertisers.

e) Not all phones have GPS. Can you think of a flip phone or candy bar phone that does?

So my first guess is a carrier lobbyist sold the reporter on it. If only they could depend on user's GPS, they don't need expensive timing methods. And if it fails, shrug.. "We tried!"

My second guess was it was the FBI. We know how they feel about anyone doing something on a phone without their knowing all about it. (Just ask Tim Cook!)

Could this be the precursor for mandatory GPS use? Or a "fix" so the FBI can enable your GPS remotely? Donno...

***** Moderator's Note *****

  • In this context, I think "YKW" means "You Know What."

I didn't know that the GPS in a cell phone could be disabled. When did that start? Who can do it?

Why do you say "It does not provide the PSAP with the floor or room?" I though GPS could repost altitude, and that "GPS-enabled smartphones are typically accurate to within a 4.9 m (16 ft.) radius under open sky."(1) Isn't that enough to get to a single floor in one building?

Bill Horne Moderator

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On any smartphone I've seen, GPS is an easily controlled setting. Android usually says "Location" on the settings menu.

Often no. You need at least 3 satellites to get a Lat/Long fix. But altitude is far harder to get close; more birds are needed to do so. Open air easily gets you >>3 satellites. But inside a building is harder. Plus you have the issue of how long it takes to get an initial GPS fix. That can be up to 12 minutes.

Suppose you are in the windowless core of a building. You may be under a cell on the roof, or the next building has one. Or the building has a cell repeater. The GPS birds are at the best 12,000 miles above you and far far weaker. Slant range birds will be further away but you need those birds to get a GPS lock; the further they are, the more accurate the fix will be.

The carriers may use Augmented GPS as one helper.

A further complication: Many smartphones/carriers allow calls over WiFi when it is available and cell coverage is weak/saturated. The carriers must love that -- a WiFi call does not tie up any of their expensive RF resources; instead the user/building provides the TCP/IP bandwidth to the carrier. (Note: If you are on a per-minute cell plan, the nice carrier likely *still* charges you on WiFi calls.) I have no idea what address data the carrier passes to the PSAP (Public Service Answering Point) in such a case. But consider being on a huge campus network such as the GooglePlex or Ohio State University.

(All of this is why I got my nephew with a small child a VOIP account and a Western Electric 2500 set for their house, and confirmed the registered dispatch address is correct.)

Now sometimes the carriers sell you picocells you plug into your home Internet feed. They are designed to only initially register after the GPS inside the picocell has a lock; thereafter it CAN tell the PSAP the caller is within its tiny range.

I suspect the article came from recent legislation; as of this month, Sec 506 of Ray Baum's Act requires the PSAP get the "dispatchable location" of a 911 call. That means address, floor, room #. Plus, the

911 call must also tell the front desk/security office of the call. (I assume that's so the responders can be escorted to the caller's room.) Most PBX systems now in use can not do this.

In summary:

1) Not all calls provide GPS data 2) The carriers are required to provide a "dispatchable location." 3) How?
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On my plain cell phone, I may disable the GPS so that other people may not see where I am. However, I cannot disable it to prevent the cops from tracking me.

I should note that for cops to be able to track someone's cell phone location, they need to have upgraded equipment to do so. Not all departments invested the money to do this.

My feeling is that if someone is in any kind of trouble needing 911 help, they should attempt if at all possible, to know as much as their specific location to pass it along to the 911 operator. Hopefully other people would be around who could provide assistance, especially in a large building.

Some large organizations have trained their security staff on how to handle 911 emergencies, such [as] having doors wide open, having elevators on standby, and directing rescue personnel to the specific spot to save time. Big help. But not all places do this.

One frustration is that some areas have consolidated their 911 call centers, so they now serve a large geographic area. That means the operator might not be familiar with a particular shopping center or a residential street name that may be duplicated from one development to another. Computers are supposed to keep this all straight, but sometimes the programming or data isn't adequate or the caller can't help. "I'm at the McDonald's on Rt 100" won't be enough if there five McDonald's along the full length of Rt 100.

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My gravel road starts on a major highway, wanders 3 miles into the woods, then 2.5 miles back to a secondary paved road. The secondary paved road connects to the major highway a mile closer to "town" than the other end of my gravel road. I live half a mile from the secondary paved road and that half mile is the only part of my road that is well maintained.

The only time in 50 years that I've had to call for an ambulance, the GPS directed them to the end of my road that connects to the major highway. So they had to thrash 5 miles over icy frozen ruts to reach me. They could have used the secondary paved road route for a total of 3 fewer miles, none of it over poorly maintained surface.

So the location (911 via land line) worked perfectly but the routing was problematic.

The fire department is local volunteer who would know the best route. Emergency medical is staffed from a wide area and dispatched from the local market town 13 miles away.

Just an anecdotal data point,

Reply to
Mike Spencer

The other issue, particularly in urban areas, is multipath. As GPS depends on measuring time-in-flight, reflections from nearby buildings and within a building will severely reduce accuracy. You can see this in vehicles with GPS mapping systems. In urban areas with tall buildings it isn't uncommon to see errors of a city block or more.

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Jay Hennigan

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