I hear about people being found using this technique. Is it now routine to equip SAR teams with gear that can ping the cell phone of a stranded hiker?
Thanks,
Rob
A lot of place that are popular for hiking have no cell phone coverage. Many emergency responses are triggered by cell phone calls, but often you just have a report of a lost hiker. I haven’t heard of S&R teams in the northeast having this technology, but it’s possible I suppose. It’s just not going to be useful in a lot of situations.
Just because the area doesn’t have cell phone towers doesn’t mean that the SAR can’t have their own portable “tower” for the purposes of pinging a cell phone, does it?
Thanks,
Rob
Need answer fast?
an active cell phone is still a radio source good for half a mile or so. My EMT days predate most cell phones but I don’t see why present day radio direction finder gear could not be very helpful especially when combined with aircraft. Problem is, by the time most people are really lost, the cell phone is dead.
Good point. Part of what helps with cell tower information is that you can look at past records, so you may get information even if the phone is currently dead.
-D/a
Not necessarily-- My phone can go for nearly a week between charges. And it’d probably be more, if I turned it off. That’d be plenty of time for a person to get lost and for both the hiker and the outside world to realize there’s a problem.
If you are out of cell phone range you are most likely keeping your phone off to save batteries. In cold weather, battery life is shortened a lot so you would only turn on your phone to check if you had signal and then to place a call or send a text (which is often possible when a call can’t be placed). But if you are lost and in need of rescue and you don’t have signal you’re probably going to keep your phone off.
That could change if this technology is deployed, but I would suspect it’s only useful if you’re in a chopper and can cover large areas quickly. In rough terrain I suspect the signal range would be reduced considerably. People tend not to get lost on top of mountains, but down low in tangled terrain.
A lot of S&R is for small kids. And, most of the time the phone must be on.
In the ones I went on, this wasn’t even something they talked about.
Some of this depends upon the phone’s protocol, but the principles should remain. For GSM this will certainly be true. Phones do not transmit all the time, so a simple direction finder won’t see any signal to find a direction. If a phone is in reach of a cell it simply sits and listens (camps) to the cell. Very very infrequently it will wake up and chirp a short (few seconds) message to the cell. Where infrequently is measured in hours. If the phone is not yet camped it continues to transmit as part of the camping protocol, this however will drain the battery in a few hours.
This leaves you with the problem. If the phone is in range of a cell, all that is needed is to call the phone, and have the cell work out the phone’s location based upon time of flight. If the phone is not in range of a cell it will either be off, or the batteries will be dead. If you need quite precise information about location, having narrowed it down with the cell’s information, an on the ground direction finder might be useful - but only if the phone was in a call, or otherwise engaged in active transmission.
A smart phone that is looking to see if you have you email or the like will be a slightly better bet, but even then, it will only wake up periodically and make a very short transmission.
If a modern phone is not in the range of a cell it does not transmit at all on the cell phone frequencies. Phones need to listen to a base station to learn what frequencies and what time to transmit. Modern smart phones may be transmitting on blue tooth or wifi frequencies but those are very low power and therefore hard to detect at ranges greater than a few hundred meters.
If the person in need of rescue knew that the searchers were looking for his phone, is there a strategy he could employ to affect his rescue? Turning it on and off once an hour, say?
Thanks,
Rob
If you knew the rescuers were close by (could hear the helicopter or see lights) and you knew they were carrying this gear it might make sense to turn your phone on. But you’d have better luck flashing your own headlamp, lighting a signal fire/flare, or signaling from a mirror if they were that close. Or carry a Personal Locator Beacon (PLB) which are designed specifically for this situation and will work pretty much anywhere, anytime.
Among all my other cockamamie invention ideas is one for just that sort of situation. During a search & rescue attempt when a person is lost in the wilderness, why not send up several tethered weather-balloon-type things with cellphone transmitters/receivers/repeaters attached to them?
They could be very brightly colored with flashing lights so that the lost person would know to turn their cellphone on and make an emergency call, or even make their way to the tethered base if they are close enough where they could activate a device that informs rescuers that they are at that particular tether. There could also be some emergency supplies at the base of the tether.
Since the devices would be high up in the air, line-of-sight wouldn’t be a problem. The only potential problem would be getting them close enough to where the lost person is.
I don’t know exactly how far cell phones can transmit but any distance problems could or would be mitigated by:
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The altitude of the balloons. If they are in line-of-sight of the phone then (I’m sort of guessing here) a phone should be able to reach them from further distances than a phone’s normal required proximity to a cell-tower because in normal use, cell towers aren’t always in line-of-sight so the signal must sometimes bounce off of things.
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Using stronger/more sensitive receivers (if they exist) in order to pick up weaker signals at greater distances.
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The number of balloons put up. Obviously the more you float, the better chance you have of picking up a cellphone transmission from an unknown location.
Please refer all congratulatory hugs, kisses, and bundles of cash my way. Don’t steal my brilliant idea for yourselves!!! 