E911 Cellular GPS

[mike1]

So this dude told me once that you could dial 911 from anywhere as long as you could see sky because the new E911 system uses satellites. I kind of forgot about it until we had to have a member of our climbing party helo'd out of the North Cascades last summer. We tried the cell's but couldn't get out until one of us climbed up towards Formidable and hit a tower. (you'll have to wait for the next publication of the ANAM if you want the story). Anyway, I recently upgraded my cell to a Motorola 325I which seems to have the best range of anything out there and I thought I'd look into this E911 thing. The one thing I can't confirm is whether or not the cell calls out to 911 use satellites for communication. My guess is that you still need a cell tower BUT once you have signal, your cell phone will use GPS satellites to send a rough location to the 911 system. Like I said, that's my guess. Anyone out there KNOW how this system works?

[ronco]

You are right. Cell phone 911 GPS requires access to a cell tower in order to make the call. It does use the GPS satellites to calculate its location. I think most of the phones don't even have a full stand alone GPS built in. They use the cell tower signal as part of the process of determining location. I also recall that maybe some of the processing is done by the cell site. I think it's referred to as 'cell site base station assisted gps'

 

ronco

[goatboy]

Mikester, are you on Verizon or what? I've always heard that Verizon was generally the best for remote mtn cell service...

[woodchips]

Nextel has a genuine GPS chip in some (maybe all) of their phones. I've played with it a few times, and it seems to work OK with no tree cover, but pretty slow. I wonder if any of the newer/ higher end phones have better GPS units?

 

Mikester, are you on Verizon or what? I've always heard that Verizon was generally the best for remote mtn cell service...

 

I'm curious about this too, I'm in line for a new phone, and will be in mostly in the N cascades and Olympics. Any suggestions?

[mike1]

I do have Verizon, but I didn't bring my phone into the Cascades. I don't know what coverage the phone that got out on Formidable was.

 

Before I picked out my recent upgrade phone I did a little research and found the consensus was that the Motorola 325I was the phone to get for coverage. I found a few cellular forums that spoke positively about it. It’s one of the last phones made that still uses analog (trinet I think) which can reach further than digital. They will stop making phones next year with this capability. I picked this phone up and will give it a go on the Ptarmigan in July. So far I really like it.

 

It’s funny to me that the cellular phones are cutting back on things like coverage to make room for stuff like internet surfing and all the other bells and whistles you can get now. You’d think with technology now they could and would want to improve coverage.

 

All new phones are required to have the GPS system according to the FCC >http://www.fcc.gov/911/enhanced/. I don't know if there are better GPS units in other phones. I've heard the accuracy range is up to 100 meters.

 

[jhamaker]

Location accuracy is often better than 100M - but usually only available to some 911 operaters in some cities and only if you have cell coverage and a clear view of the sky durring a full moon. I know of a rescue off of McClellan's Butte last yr (yes, right on I-90 just out of N Bend, WA) and 911 was unable to find the location.

 

Seriously, if you find a cell phone that can give you good location accuracy when there is no cell coverage, let me know.

Edited June 11, 2007 by jhamaker

[NBbeater]

E911 locations can be quite good, but often the 911 operator will not get a location even with good coverage and a phase II phone. The last lost person I know of was 1.8 miles from where the cell system said they were. The worst I've seen was over 5 miles. Some have been within a quarter mile....