911 on Wireless 911: new study finds poor performance in locating wireless 911 calls

I wrote about it here and here re: how lousy Ohio’s doing on this front. Next month, a new first-ever report will be released that will indicate just how serious a problem the failure of locating wireless 911 calls is.

Here’s the story from the AP. Read more about the Association of Public-Communications Officials – the group that requested the report, here. Read about APCO’s Project LOCATE here. Read about the funding source, Public Safety Foundation of America, here.

This line in the AP story says it all, and repeats what the other articles posted last month said:

While the report pointed out the generally poor performance of the wireless industry in locating 911 callers, it also pointed out a need for 911 call centers to work closely with providers and the importance of public education.

A new generation of telephone customers is being raised without using land-based telephone lines. But they still expect rescuers to be able to find them.

The issue has become more critical as the number of 911 calls from cell phones exceeds those coming from land lines, public safety experts say.

CTIA reports that 230,000 calls to 911 are made from cell phones each day. The group also estimates that 8.4 percent of households are “wireless only.

Ohio legislators: do not say no one told you.

One thought on “911 on Wireless 911: new study finds poor performance in locating wireless 911 calls

  1. Jill:My career was spent in telecommunications, including a stint as VP/Global Operations for one of the largest data networks existing prior to the Internet. I won’t paint myself as a cellular technology expert, but I understand a good deal more than most folks.The only truly accurate way to locate a cellular phone is if the cell phone itself knows where it is. This is best accomplished by having a GPS receiver and appropriate software in the cell phone. Then when a 911 call is made, the GPS coordinates of the phone can be automatically transmitted to the emergency services agency.When a cell phone is on, it is constantly in contact with the cellular network, even if you are not using it. The phone has to stay ‘registered’ with the network so that when someone calls the phone, the network knows how to route the call — how to find the phone. So some people, including me, are concerned that when a phone has GPS capability, you can be tracked at all times. I don’t intend to buy a cell phone with GPS ever, but I think at some point there won’t be a choice.But without GPS capability, the only shot the network has of locating a cell phone is via the ‘triangulation method.’ Do remember the old US Forest Service movies where they showed fire spotters locating fires by looking through a device mounted high in a tower? It took at least two spotters in two towers to pull it off. Each one would radio in the direction the fire appeared to be coming from in reference to their location. Then someone with a big map would draw a line from each tower, and where the lines intersect, that’s where the fire would be. Two works, but three is better (hence the term triangulation). In fact, the more towers that report in, the more accurate the results.The radios in cell towers can’t determine direction, but they can measure signal strength. So if more than one cell tower can ‘hear’ your cell phone, they can compare the relative strength of the signal and guess where you might be.Think of it this way, instead of drawing lines from the fire tower, you would draw circles around the cell towers, with the radius representing the strength of the signal. Theoretically, the phone would be where the circle from the first tower intersects the circle from the second tower. But there’s a problem – there’s two places those circle intersect, and they could be miles apart.But the phone isn’t necessarily at the one of the intersections. All kinds of things can affect signal strength, so the phone may really be nearer or farther away than the measurements would lead you to believe. So you can’t concentrate on the two intersection points. All you can say is that the probability is that the phone is somewhere around the area in which the two circles overlap.With more towers in range, the size of the probability area decreases, but towers are spaced according to how many phones are typically active in an area. So towers are much closer to each other in cities than in the boonies.The point isn’t to give an engineering lesson, but rather to say that we can’t legislate the capabilities of technology. In the case of locating cellular 911 callers with today’s technology, it’s a trade-off between carrying what amounts to a always-on personal tracking device, and not being able to locate 911 callers from cell phones.Sometimes, I don’t want Big Brother to know where I am.PL

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