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#154539 - 09/11/11 09:08 PM Do cell phones provide any GPS locator capability?
lori Offline
member

Registered: 01/22/08
Posts: 2801
I debated putting this in safety, or beginner, subforum. I think it's more general.

I have read on a number of backpacking forums that people think their cell phone will provide location in the backcountry even if there is no coverage to make calls.

The short answer to the question is "not really."

The long answer involves lots of techno-speak about the progression of cell technology, FCC mandates for providers to obtain lat/long coordinates of the cell user (this is still not possible in some areas), and the kind of phone you have.

Cell phones, when on, typically ping every thirty seconds. (A ping is a request for connection that verifies a connection is possible - it's a network test. Why your cell phone knows there is no network available.) Records of pings are only kept for 24 hours. Unless you text or make a call - those are permanent records.

If the cell phone is within range of a tower, and that tower has not yet been upgraded or is communicating with an older phone lacking appropriate tech, the cell company may get information on the approximate area the cell phone is in. Imagine a pie cut into thirds. This will give them an indicator of which third of the pie you are in. Not a specific location. Narrows a search down, but if you are within range of the tower you should be able to call out.

If the tech at hand has been upgraded to more recent FCC requirements, the cell company may be able to get a lat/long coordinate for the cell phone. This is also going to happen when the cell is within range of a tower.

Any position a SAR team receives is considered the last good fix - subjects may still be moving at a rate of 2 mph in any direction, after all. Direction of travel can only be ascertained if another tower connects with the cell phone.

Some areas have a multiplicity of towers from varying providers, which leads to a multiplicity of paperwork and calls to get fixes from any of them. This will slow progress in obtaining useful information. Even with one provider unless the agency requesting information has an established relationship with the provider, it's difficult, slow, even impossible to obtain location information.

In mountainous/wilderness or rural areas, cell towers are frequently along roads - this worsens accuracy with location tech in cell phones. Optimal configuration of towers for accuracy is to have towers arranged so that cells overlap or abut each other closely - towers strung out all in a row are less accurate.

In short, there are too many variables to make cell phones a dependable means for search/law enforcement agencies to locate a subject. Plus, the cell phone needs to be in range of towers. In places like the central Sierra, you leave the towers far behind. Unless you are in Yosemite where there are towers in the valley and in Tuolumne Meadows.

This information is loosely summarized from information provided by resources within my reach by Search and Rescue. Anyone can find specifics in a variety of sources; the one in front of me at this time is an appendice in Lost Person Behavior, one of the primary resources for SAR persons.

We have had one search this year where the subject was in range of a tower. We spoke to the subject on the phone, advised them to build a fire, and our team walked in the dark up the hill to them, to guide them back to the trail and out of the wilderness. Obviously they were not far out. This was far more expedient than all the rigmarole necessary to pull location information from the provider.
_________________________
"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzuki

http://hikeandbackpack.com

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#154542 - 09/12/11 12:09 AM Re: Do cell phones provide any GPS locator capability? [Re: lori]
Rick_D Offline
member

Registered: 01/06/02
Posts: 2801
Loc: NorCal
Good stuff Lori, and good input from the S&R perspective.

I carry a cellphone--barebones flavor--for familial reasons but only get reception when I'm able to see the I-80 corridor or on some peak high enough to snag a signal. Which is to say, maybe 5% of the time.

I'll add that typical smartyphones have separate GPS functions, with processor and antenna. These couldn't care less whether there's a cell signal and will indeed emulate a GPS. However, the antenna and processor are nothing like a handheld unit so you shouldn't expect Garmin-like performance.

Behold, the sorta mighty iphone4.

iphone4 GPS gutz

Cheers,
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#154547 - 09/12/11 09:42 AM Re: Do cell phones provide any GPS locator capability? [Re: lori]
oldranger Offline
member

Registered: 02/23/07
Posts: 1735
Loc: California (southern)
Very informative. Way back when, we didn't have to worry our pretty little heads about this stuff. But time marches on....

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#154551 - 09/12/11 10:45 AM Re: Do cell phones provide any GPS locator capability? [Re: lori]
mana Offline
member

Registered: 06/16/11
Posts: 24
Some good info here, thanks!

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#154557 - 09/12/11 02:06 PM Re: Do cell phones provide any GPS locator capability? [Re: lori]
billstephenson Offline
Moderator

Registered: 02/07/07
Posts: 3865
Loc: Ozark Mountains in SW Missouri
Some newer phones have a built-in GPS capability. They have a GPS antenna and the software to acquire a pretty accurate Lat/Long. You have to turn on the GPS in your smart phone's "Settings" or "Preferences", by default it is usually turned off.

Most smart phones need a network connection to download a map to show you, in a graphical format, exactly where you are.

It's odd that you bring this up today though, because I just wrote the code to grab that data from a GPS enabled smart phone last night. I'll probably add a feature that will place your location on a map tonight sometime.

In the meantime, if you have a smart phone with a GPS, and you want to test its accuracy, you should be able to get your lat/long from it here:

http://navigraphic.com/locate.html

_________________________
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"You want to go where?"



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#154566 - 09/12/11 05:44 PM Re: Do cell phones provide any GPS locator capability? [Re: billstephenson]
lori Offline
member

Registered: 01/22/08
Posts: 2801
The GPS connectivity being one way means only that you'll have your coordinates... unless you also have a cell tower to connect to so you can call us and tell us. But at least it's something.
_________________________
"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzuki

http://hikeandbackpack.com

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#154577 - 09/12/11 07:25 PM Re: Do cell phones provide any GPS locator capability? [Re: billstephenson]
Paulo Offline
member

Registered: 01/27/11
Posts: 158
Loc: Normally Pacific Northwest
Bill is right. Most of the new Android phones have built in GPS units that provide decent GPS, but not nearly as good as some of the dedicated GPS units.

HOWEVER, be aware that many applications for the GPS rely on cell tower access to dynamically download the maps. I.E. if you can't get data tower reception it can't download new maps and you're hooped.

Double check that a) your phone really does have GPS and doesn't use the method lori describes and B) make sure that your application maps are preinstalled and that it doesn't load them as it needs them.

I recently went backpacking up in washington and although my brother in law had a GPS enabled cellphone AND preloaded maps it sometimes took up 3-5 minutes to get a signal. It works, but don't be in a hurry.
_________________________
Without a doubt, the hardest thing of all in a survival situation is to cook without the benefit of seasonings and flavourings. - Ray Mears

http://theoutdooradventure.net

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#154586 - 09/12/11 11:23 PM Re: Do cell phones provide any GPS locator capability? [Re: lori]
billstephenson Offline
Moderator

Registered: 02/07/07
Posts: 3865
Loc: Ozark Mountains in SW Missouri
Originally Posted By lori
The GPS connectivity being one way means only that you'll have your coordinates... unless you also have a cell tower to connect to so you can call us and tell us. But at least it's something.


That's absolutely true Lori, and I should have mentioned too that your post is well thought out and your points are very valid.

I should have also pointed out that the link I provided in my last message uses "Geolocation". That means that the software that runs the page I linked to will first try to use your device's built-in GPS, but if its not turned on, or not receiving a signal, or you don't have a built-in GPS, it will then try and use other methods, like Google's Location Services, which may use cell towers, your IP address, wifi networks, etc, but they won't be near as accurate as a GPS.

If you're looking for an ice cream shop, the geolocation features on your smart phone can work just great to tell you where there are some nearby, if you're lost in the mountains and need help, its not always so great for the reason you point out.

That said, I have used my Android phone's GPS with free mapping software and it really works pretty good. Better than I expected. Sucks up the batteries though....

And, I think you'll find the little "Radar" app I'm making will have some value too. The real beauty of "Smart Phones" and "Apps" is that they can be tightly focused on a specific purpose, and anyone can make one. So, while there are those who are working hard on making cool GPS mapping apps for hikers, others, like me, can work on one for hikers that's just for weather, and you can choose the ones you like most from all of them.

I see great things happening because of web enabled smart phone type devices. You certainly have to be aware of their shortcomings, but at the same time you can take full advantage of what they offer.

One of the best things about them is, once you have your device you can carry as many apps as you want and they don't add any more weight laugh
_________________________
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"You want to go where?"



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