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Backpacker Magazine – Online Exclusive

Prof. Hike: This Post Might Save Your Life

How your cell phone calls for help even when you don't have service

by: Jason Stevenson, author of The Complete Idiot's Guide to Backpacking and Hiking

professor hike
Got a Question for the Prof?

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You’re lost, stuck in a ravine miles from the nearest road. Hoping for a quick rescue, you power up your cell phone. Dang. No signal. Discouraged, you turn it off.

Wait. Did you just make a huge mistake?

Even if your phone has no service, attempting to dial 911 or leaving the phone turned on intermittently could transmit an electronic lifeline that lets rescuers know you’re alive.

Here’s how it works.

In the ideal scenario, calling 911 on a cell phone connects you to the nearest PSAP (public safety answering point). Before the 911 operator can ask, “What’s your emergency?” a computer has already triangulated your latitude and longitude coordinates to within a few hundred feet using signal telemetry, your phone’s GPS chip, or both. It even assigns your location a degree of error. If you’re a lost hiker, the 911 operator transmits that position to local police and SAR teams so they know where to find you.

But what happens when your 911 call doesn’t go through?

Well, the wireless provider may still have recorded the exact time you activated your phone to make a call. Before any call is initiated, a cell phone and the nearest tower greet each other with a digital “handshake.” Unlike voice calls or text messages, these electronic packets require very little energy to send or receive. Sometimes these handshakes transmit when your phone indicates no reception. Sometimes they bounce off towers that your phone doesn’t have permission to use. And sometimes they get through when they shouldn't–like in remote and mountainous terrain. Different cell towers and nodes can share these handshakes, too. In almost all cases, the data trail is logged and saved on computers owned by wireless service providers. When someone goes missing, law enforcement officials can find out that person's cell phone number, call the service provider's special emergency hotline, and access the data trail for a specific phone.

What does this mean for lost hikers?

It means your phone can contact cell towers—sending and receiving tiny electronic breadcrumbs—even if your ability to communicate is zilch. That could let rescuers know that you're alive and to continue searching. Note: This is why you should include your cell number and network provider with the itinerary details you leave with trusted family and friends. (For a real-life case study of a rescue in which "digital handshaking" helped save a lost hiker, check out our upcoming May issue.)  

Keep in mind, however, not all SAR members know about these hidden messages that cell phones can leave. Many SAR teams are experts in lost-person behavior. They know how people are drawn to linear terrain features like roads and rivers. They know to interview friends of family to develop a search profile. And many rescuers are outfitted with high-tech navigation and safety gear. But when it comes to communications technology, SAR teams can find themselves as out-paced as the rest of us. The November 2006 death of James Kim in Oregon is one example of family members blaming rescue leaders for ignoring technology. The arrival of more powerful cell phones, and even satellite-enhanced smartphones, suggests the complexity of this problem will only increase. In a perfect world, better technology means more lost hikers are rescued. But we all know the imperfect ways that technology meshes with nature.

So what should you do?

If you own a cell phone, bring it on every hike. Before you leave, give your phone number and service provider to your check-in contact. Plus, don’t think that a cell phone or GPS is a substitute for a good map and accurate compass. Keep your phone turned off during the hike, but power it up occasionally to check for service (and to drop some digital breadcrumbs). If you become dangerously lost or injured, dial 911 even if you don’t have strong service. For better service, head for higher ground—cell phones operate by line-of-sight radio waves. And finally, just be careful out there.

Got a question? Don’t dial 411. Post a comment or send an email to

—Jason Stevenson

idiot's guide to backpacking and hikingJason Stevenson is the author of The Complete Idiot's Guide to Backpacking and Hiking

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Apr 11, 2014


Apr 11, 2014

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Nov 09, 2013

Being physically challenged, this gives me some comfort having this information. Not that I would expect myself to be in such back country situations, you never quite know if you might situationally or ill will end up being in such a quandary. Thank you for posting this. I often watch crime shows where they follow pings. So I googled. Glad I did. Again, thanks!

Sherryl Bishop
Apr 10, 2012

As I'm a hiking fan, I consider this post to be very important and useful. It can really save lives, so thanks for that from all people who like spending their free time hiking!)))Your mobile phone can rescue you as well as ringtone maker Everybody, stay safe while traveling and have a good time!

Yours, the employee of

mkv player
Dec 14, 2011

This is really useful! Now that I know how to call 911 I feel much safer.

Jul 19, 2011

On a dual band phone when you do not have service from your provider the phone will try to use the other band to make emergency calls. For example if you are hiking in WV where there is little CDMA coverage and you dial 911 the phone will switch to GSM and attempt the call.

I've done this on a Blackberry Tour (GSM/CDMA).

Apr 19, 2011

Would an old, out of date phone work, if only to dial 911 & provide a signal?

Apr 02, 2011

Small correction, cell phones do not operate via line-of-sight radio waves. 'Tunneling' or 'Beam' based communications work that way such as most Sat Phones, but everyday cell's normally only work due to bounced or penetrated signals.

A quick suggestion, if you are going to take your cell phone on your hike... take a bluetooth headset with you too. If you can't get service on the ground, but can get your phone lifted into a tree via rope or whatever, then you can still use the wireless headset to communicate with emergency services.

Seriously though, depending on where you are hiking, you may be able to borrow a SPOT or such from local authorities before venturing out.

Also, another small correction to a previous comment. Almost no cell phone's still in operation in North America (or sold there) increase transmit power when searching for service,... they pretty much never did. What they did do was drop to analog to find service and analog is no longer in operation and all phones with analog service should have been deactivated at least 2 years ago. Now a days digital only phones have a single output power that they always use despite the quality of service received. The general exception to this is World Phones that have GSM and CDMA, each technology uses a different amount of power, so consumption might go up and down and the phone switches back and forth.

Mar 30, 2011

Thanks for the amazing Article.
Very useful information.
Also, thanks to all the comments posted by respected users. Very valuable information.

Mar 26, 2011

Actually, I am on a SAR team in the desert and we have used cell phone pings to locate missing hikers. It gives us an idea where to look, even though the area id huge. For example, we began searching in the obvious spots on day one (duh) and when we got the tower read out we realized his phone had pinged and we were too far out. So please, take your phone.

Mar 17, 2011

So now my somewhat evil boss can track me even after I've gone out of my way to get out beyond "normal" cel phone range - you know, those job "emergencies" that come up when you're on vacation. I'm going to bury that phone in a nice waterproof box near the trailhead next time out. Thanks for the warning!

Mar 11, 2011

@ Doug
The "electronic gadgets" are simply tools which when used right can be a big advantage. Things do evolve you know. Like modern clothing materials or winter gear. It would be quite wrong to not take advantage of them. Or do you still sport some wooden ski's? But yeh, back in the days everyone and everything was better right?

Mar 08, 2011


There's obvious value in being able to contact SAR immediately if you're seriously injured and can't move. I guess in your day you just took it like a man and died.

Feb 27, 2011

Ms. Nixon, no most GPS are receivers only and do not transmit any information.

Feb 27, 2011

Having orienteering skills is good to have but knowing where you are does not mean you will have the ability to self rescue. All these "electronic gadgets" are a great safety net that we did not have just a few years ago.

Mrs nixon
Feb 26, 2011

Does a GPS unit send out a similar signal?

Feb 25, 2011

Somehow, when I was younger, we managed to survive in the wilderness without cell phones, gps, and other electronic gadgets. How? We developed orienteering skills based on map and compass, and on years of simply spending time in the woods and exposing ourselves to increasing amounts of risk. Not "dumb risk", but, for instance, taking trips to increasingly remote places, taking increasingly difficult routes, and spending more time dealing with nature by ourselves, and not relying on others. We now seem to be so fanatical about security that we are unwilling to take modest risks like heading into the woods without a cell phone or gps unit. We are truly becoming a bunch of insecure wimps who rely upon technology to replace the skills that ought to be in their heads as a result of our experiences.

Patrick Lilly
Feb 25, 2011

The real lesson here is that your cell phone is spying on you, even when it's useless to you for making a call! Law enforcement can find you, even if you're *not* injured, lost, or in need of any kind of actual assistance! So, yes: If you take a cell phone with you into the wilderness, unless you want to be tracked everywhere you go, take out the battery!

Capt. Red Beard
Feb 25, 2011

For those who think that SPOT is a "anywhere panic button", think again. It is nothing more then a scaled down Satellite Phone. It MUST have the ability to reach a satellite to function. Many things can block that signal. Including clouds, terrain, and a thick tree canopy.

Don't get me wrong, I think SPOT is a great product. I think that it is very helpful in many ways for many things. I don't like the false security that it may bring to those who have not fully researched it.

The best we can do is learn, and be prepared for going into the wilderness. Knowledge is usually very cheep, and the lightest, best survival tool you can have.

If you are looking for a true "panic button" look for a PLB(Personal Locator Beacon). Best one I have been able to find is the "McMurdo Fast Find 210 Personal Locator Beacon with GPS". It is $250 at REI. There are great details on their website.

Happy Hiking, and stay safe everyone!

Feb 25, 2011

Something to remember (I sometimes forget) is to turn off your cellphone COMPLETELY when leaving your vehicle and going into backcountry or rural areas to save battery life. When you're out or range of towers, your phone will try hard, increasing its power and battery consumption, to find a signal that is often not there. Some phones cannot be turned off so the only option is to remove the battery.

Feb 25, 2011

I remember reading in Backpacker that you should text multiple friends if you need help in the backcountry and have reception problems. That's supposed to leave the data needed to locate your position when reception is obtained while using less battery power.

Dennis Phelan
Feb 22, 2011

This is why I purchased a SPOT GPS transmitter that will send a message to 911 based on satellite connections not cell towers. I won't hike without it.

Feb 22, 2011

the most unfortunate thing that happened was this family's relying on using a GPS to navigate with and not comparing the route to a map...Not to sound cold but they are the ones that put them where they were and ultimately to blame for what happened


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