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Cellphones Wireless Networking Technology

New Tech May Help Find Missing People In the Backcountry Within Minutes (coloradosun.com) 90

A new tool called Lifeseeker could help search and rescue teams find missing people in minutes using their cellphones. The technology acts as a miniature cellphone tower, allowing rescuers to pinpoint cellphone locations within a 3-mile radius, significantly improving the efficiency and success rate of search missions in challenging terrains. The Colorado Sun reports: "As we detect the phone, basically a blotch shows up on the map and as we fly around that area, that blotch gets smaller and smaller and smaller until we can see exactly where they are," said Dr. Tim Durkin, a search and rescue program coordinator for Colorado Highland Helicopters. "That process of detecting, focusing on one specific location takes about a minute -- not really very long at all." Depending on the situation, search and rescue teams can then send in ground crews with the person's location or land the helicopter if there's a clearing nearby and conditions allow for a safe landing, Durkin said. During a test mission in La Plata Canyon northwest of Durango, search crews found the two people they were looking for within two minutes and 14 seconds, Durkin said.

The technology, called Lifeseeker, was developed by Spain-based company CENTUM research & technology and is in the process of being approved by the Federal Communications Commission before it can be sold to the state or counties hoping to use it for their SAR efforts, he said. [...] The radio-based technology needs a clear view of the terrain without interference to pick up the signal of the cellphone. If the conditions and terrain are favorable, it can detect a cellphone up to nearly 20 miles away. It takes about three minutes to attach the Lifeseeker unit inside a helicopter when needed for a search and rescue mission, Durkin said. SAR can also use the tool to send text messages to the missing person, for example, advising them to stay in one area if they are hurt or move to a clearing for a helicopter to pick them up. The tool also has a broadcast function that allows SAR to send out a message to a group of people within a certain range, similar to an Amber Alert for a missing child, to warn them of a wildfire or flood, Durkin said.

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New Tech May Help Find Missing People In the Backcountry Within Minutes

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  • Brilliantly simple (Score:5, Insightful)

    by undulato ( 2146486 ) on Wednesday May 29, 2024 @07:09AM (#64507265) Homepage
    One of those "wish I'd thought of that" kind of things right?
    • I feel like I saw a similar tool in "Better Call Saul" where they had a mobile tower to connect to someone's phone while they were off the grid with no signal, have a quick chat, then shut the tower down. Guess the location aspect wasn't shown there but the concept makes sense. Yes, wonder why this thing didn't exist already?
      • Airborne femtcells (Score:4, Interesting)

        by DrYak ( 748999 ) on Wednesday May 29, 2024 @08:19AM (#64507377) Homepage

        Yes, wonder why this thing didn't exist already?

        I would guess a combination of tech miniaturisation and legal red tape.

        1. small cell, that is both small enough but with enough power to cover a large range.
        Unlike the usual cell-on-wheels base station that you see deployed in trailers to, e.g., extended mobile network coverage at a music festival, this tech needs to be small enough to be quickly attached as a pod under the belly of the SAR helicopter.
        But unlike typical micro cells (picocells, femtocells, etc. which are used mostlya indoors) it still needs to have a wide enough coverage (about a couple dozen of km).
        Microcell have only appeared somewhat recently, and given the market, very few manufacturers concentrate on long-range capabilities.

        2. high spatial resolution antenna.
        You probably need something like a phased array to give some directionality sensing to the receiving antenna?
        These have only become cheap enough in recent times (think how recently avalanche transceiver have started to also similarly show approximate location instead of merely giving range) (or how spacial pin-pointing of Bluetooth - i.e.: directly showing you where the signal of an AirTag is coming from - is recent and not available in all phones).
        Without that you'd get only range deduced from signal intensity and you would need multiple helicopter carrying these cell towers to triangulate the source.

        3. regulatory
        Mobile network operates on regulated radio bands.
        It's not some 2.4 Ghz radio frequency where you could just solder a prototype in your tool sched and call it a day as long as you comply with some very low-bar simple limits.
        Just getting this thing certified would probably take quite some time between initial idea inception and official authorisation.
        Keep in mind that TFS mentions these devices are two way. They communicate to the smartphone too. It's not merely a detector of source of radio frequencies in the 4G LTE bands, this thing has to actually speak 4G LTE it self, and needs to do so in a compliant way in order to get its authorisation.

        Also:

        It took until *now* for this to become available *for mobile network*, BUT *positioning systems* like, e.g., Europe's Gallileo have already made bi-directionnal communication available (Galileo SAR's Forward Link System (FLS) and Return Link Message (RLM)) so beacons can send distress signals *to* sattelite and SAR can answer back to the beacon.

        But unlike today's smartphone based tech (which basically behaves like an extra mobile cell tower and thus works with most smartphones), those positioning system based require special support - not all smartphones are capable to uplink to Galileo SAR - and thus using those systems need forward planning and using a specific device that supports beacon functionnality (a bit like planning and using avalanche transponders), whereas tons of peopls have mobile phones in their pockets.

        • Without that you'd get only range deduced from signal intensity and you would need multiple helicopter carrying these cell towers to triangulate the source.

          Considering how mobile a helicopter is, you could almost certainly get away with just the one. Just take several readings from different locations.

          • by ceoyoyo ( 59147 )

            Or get them to text you their GPS coordinates.

            • Or get them to text you their GPS coordinates.

              This assumes that the accident that has triggered the whole SAR operation in the first place has left the victims in a state where they can easily text.

              That might not necessarily the case: they might not be conscious, etc.

              Of course, if it's just a horrible snowstorm that has forced people to shelter in place, it's a different question,.

        • by LazarusQLong ( 5486838 ) on Wednesday May 29, 2024 @10:08AM (#64507609)
          " it still needs to have a wide enough coverage (about a couple dozen of km)"

          Not really, the article states a radius of about 3 miles, or, the horizon, which makes sense as cell signals are pretty much, line of sight (LOS) A femto cell would be fine for this, but would have more capability than is needed, so would most likely draw too much power, and of course you would need special software. I worked on developing something like this for sheriffs on the texas border. Not so they could arrest illegal immigrants, but so they could save their lives so they wouldn't have to recover dead bodies, unfortunately the licensing was the hurdle that we couldn't overcome, the software ofr our device was pretty unique and was the PhD work of several post docs, but the licensing? FCC wouldn't believe that we were NOT tapping the cell phones the illegal immigrants were using! We didn't need that data, just the distance and bearing to the cell phones, because, when the illegals walking through the desert felt they could make it any further, they would call home to tell their loved ones good bye. Catching that cell call, getting range and bearing, and sending a four wheel drive truck with a couple of sheriffs and a cooler with lots of cold water in it, was what we wanted to do.

        • Why would you need any power at all? The point of this device is *receiving* a signal from a phone, not communicating with it. i.e. it needs a sensitive, directional antenna to enable radio direction finding. It does not need a transmitter.

          • I think you need the transmitter to handshake with the phone so you know WHAT phone you're receiving. Otherwise, maybe you're receiving 50 different phones from the search aircraft, including the potential rescuers, and that's not useful data. Identify the phone, then identify its direction. Use triangulation from the moving aircraft and with computer assist, it should be a piece of cake.

        • You probably need something like a phased array to give some directionality sensing to the receiving antenna?

          No need for that. All you have to do is fly in a pattern once you find a signal, keeping an eye on the signal strength. For example, if you get a hit while flying north, you turn around and fly south half a km to the west. Your signal is going to be weaker or stringer. If it's weaker, the transmitter is further east, and if it's stronger then the transmitter is further west. It's basically the

        • My 6 year old drone came with a remote that emits a 4G LTE signal up to 4.2 miles to control the drone. Of course the range varies with electrical interference, including from the atmosphere, the topography, as well as dense vegetation. The remote is about the size of Playstation 5 controller with two 3.5 inch antennas that flip out. It seems like something like the basics of the tech had been available for some time. It just never had been specifically designed or coupled with software to seek out random c
          • t just never had been specifically designed or coupled with software to seek out random cell phones.

            And the licensing.

            You can't just cobble it together in your toolshed (or have a master student build it, if you're in an academic setting), you also need to get the licensing approval for your modified software/modified hardware, before it is allowed to talk on the relevant 4G bands.

        • by mjwx ( 966435 )
          It also depends on the person who is lost having a phone that is switched on, has sufficient battery to last however long it takes the SAR bird to fly over them and has the phone on them.

          I'm from Australia, if I were going out bush I'd leave my phone in the car as it's dead weight that I'd easily end up damaging if I fell on it or had to cross water. Given that it can easily take days to find someone after they've been reported missing (which can easily be days after the event to begin with) I don't see
        • The only thing stopping this stupidly simple invention from being deployed were legal issues. It may still get pulled due to legal issues.

      • It does exist already, it's called a stingray. It's the exact same technology that police use to man-in-the-middle cell phones.
    • by chas.williams ( 6256556 ) on Wednesday May 29, 2024 @07:35AM (#64507305)
      No, it has practical limits. By the time anyone is looking for someone missing, it's very likely that the missing person's cell phone is no longer working. If you are out of range of a cell tower, such that you can't call for help in the first place and provide precise GPS coordinates, your phone has been busy running at full power trying to contact a cell tower.
      • by torrija ( 993870 )

        I agree this technology has limitations, but even with these limitations it can increase the chances to find a missing person.

        About the battery draining when off-grid, this can be an issue when the person is missing for few days. Where I live we are encouraged to contact emergency services as "sensibly" soon (maybe couple of hours) as possible. This also increases the chances of finding that person, regardless if that person was carrying a cellphone.

        • by Rei ( 128717 )

          Also, most people, stranded without cell signal, don't just leave their cell phone on futilely trying to contact a cell tower until the battery runs out. They shut it down and then turn it on at regular intervals to see if they then can get a signal (at a later time or different location)

          • Also, most people, stranded without cell signal, don't just leave their cell phone on futilely trying to contact a cell tower until the battery runs out. They shut it down and then turn it on at regular intervals to see if they then can get a signal (at a later time or different location)

            They also ignore any incoming phone calls [cnn.com] so as not to use up their battery.
            • by Rei ( 128717 )

              Yeah, people tend to go crazy with over-rationing when lost. Like people who die of dehydration in the desert who are found with water still in their water bottles because they over-rationed it.

            • Sending a text message would use less battery and immediately show up after the phone had been off. Why would rescuers only try to call?

          • It really boils down to if the person has sense. A sensible person would limit their cell phone usage when lost. However, there have been a few times when I am hiking up a difficult mountain trail and encountered people attempting the same hike who didn't even carry a single bottle of water with them.
          • That will make it hard to triangulate that person since you have no idea when they will power up their cell phone.
        • by GoJays ( 1793832 )
          Whenever I am in the backcountry, I always carry a battery pack that has solar charging capabilities. The pack can fully charge my cellphone and Bluetooth speaker 5 times before needing to be recharged. I usually just lay it out in the sun or hang the solar panel off of my pack while hiking and it will fully charge in a day or two. With that said, I've never had to do a full recharge of the battery pack as it is almost constantly recharging while there is daylight.
      • by Bert64 ( 520050 )

        Assuming your phone was on in the first place. If you're going somewhere you don't expect to have cell service it makes sense to turn it off or put it into flight mode. If you're prepared for the trip you also carry spare battery packs and/or a small solar charger.

        If you need to call for help you turn it on and try, or turn it on if you can hear the sound of helicopters nearby.

        • by necro81 ( 917438 )

          Assuming your phone was on in the first place. If you're going somewhere you don't expect to have cell service it makes sense to turn it off or put it into flight mode. If you're prepared for the trip you also carry spare battery packs and/or a small solar charger.

          Unfortunately, the people most likely to need rescue are the ones who would not think of this beforehand. My local newspaper has a story nearly every week: folks from out of town setting off on ambitious hikes above treeline...in running shoes,

          • by LazarusQLong ( 5486838 ) on Wednesday May 29, 2024 @10:14AM (#64507627)
            when i was in Colorado Outward Bound, we were climbing Mt Sneffels and a family showed up, in t-shirts and sneakers, by the time they had gotten to the top, following us and using the ropes we had spiked in to get over the more difficult parts of the climb, the weather had turned and instead of 50's/60's at the top, with about a 30 mile an hour wind, it started raining/sleeting... so we did a rescue of that family and bring them off the mountain... it was in the 80's at the foot of the mountain and they had thought it would be the same at the top! Plus the weather report for the day was sunny and 80's and they thought that meant on the top of a > than 14,000 foot mountain
        • Assuming your phone was on in the first place. If you're going somewhere you don't expect to have cell service it makes sense to turn it off or put it into flight mode. If you're prepared for the trip you also carry spare battery packs and/or a small solar charger.

          If you need to call for help you turn it on and try, or turn it on if you can hear the sound of helicopters nearby.

          When I go camping, I leave my cell phone in the car, powered off. There's no point in carrying it as there won't be any signal in the back-country.

      • by Anonymous Coward

        No, it has practical limits. By the time anyone is looking for someone missing, it's very likely that the missing person's cell phone is no longer working. If you are out of range of a cell tower, such that you can't call for help in the first place and provide precise GPS coordinates, your phone has been busy running at full power trying to contact a cell tower.

        Yet the pool of phones this tech, and thus these limitations, apply to is going to shrink greatly going forward.

        Every iphone sold since the 14 (the end of 2022) and most all android phones sold since that same time (and more models to come) support LEO satellite connectivity for sending SOS beacons. Cell towers are no longer a dependency.

        While yes, today that isn't a great number of phones, it will increase year after year going forward and at the same time lessen the need for this particular tracking metho

      • My first thought was that it should be called Cellseeker instead of Lifeseeker, because if your cell phone is dead it will never find you no matter how alive you are. Ironically it would be infinitely better at finding a dead person whose cell phone still has a charge.

      • Thatâ(TM)s really not true. Itâ(TM)s not uncommon for hikers to phone in that they are lost. Itâ(TM)s common practice for hikers to say âoeweâ(TM)ll be back at this trail head at this timeâ to someone else, which means a search often gets started within hours of them going missing.

      • By the time anyone is looking for someone missing, it's very likely that the missing person's cell phone is no longer working.

        You know not everybody is relying on oderl generations of Apple iPhones that needed to be plugged multiple times during the day, right?

        Jokes ditching on Apple iShiny's terrible battery life of early products aside, the people wandering out in the wilderness are more likely to carry phones with at least some battery life.

        your phone has been busy running at full power trying to contact a cell tower.

        So by that point your smartphone battery level might be at 40%.
        (Or your Nokia 3310's battery might still be at 90% - if you remembered to charge it once, last decade).

        Jokes aside:
        - on modern

      • it's very likely that the missing person's cell phone is no longer working

        You are assuming the person did not have enough sense to put their phone in standby or airplane mode and used it sparingly to attempt a signal. They could also power down the phone as well to save battery.

      • No, it has practical limits. By the time anyone is looking for someone missing, it's very likely that the missing person's cell phone is no longer working. If you are out of range of a cell tower, such that you can't call for help in the first place and provide precise GPS coordinates, your phone has been busy running at full power trying to contact a cell tower.

        This isn't a movie where the protagonist just helplessly watches as their battery drains to zero.

        If I'm missing (with no cell signal) I'm turning off my cellphone off (or putting it in airplane mode) to preserve power, only turning it on occasionally to see if I have a signal.

        If I saw a helicopter flying around that would probably be a circumstance where I'd turn it on.

        As for the OP "why didn't I think of that" I'm sure a lot of people did think of that. But the S&R crowd is pretty small, meaning the se

    • by AmiMoJo ( 196126 ) on Wednesday May 29, 2024 @07:40AM (#64507325) Homepage Journal

      I remember the idea had been floated some time ago, but the issue is always that regulations don't allow people to carry around unlicenced moving cell towers. Credit to these guys for putting the work in to make it into a product and get that product approved.

    • Or you could fit to a drone equipped with a hand-grenade?
  • That is one very valuable tool for SkyNet.
  • by Kelxin ( 3417093 ) on Wednesday May 29, 2024 @07:34AM (#64507301)
    For finding people that don't want to be found also....
    • by torrija ( 993870 )

      If you don't want to be found it's likely that you won't be carrying a cellphone. Or at least that phone will be off and with lots of tin foil around.

      • One would think -- but if you are a stupid criminal and get found this way, good on the cops. But hey, the number of people who commit crimes and post to social media...
    • by Ed_1024 ( 744566 )
      That was one of my thoughts too. Just guide the Terminator warhead from the Lifeseeker (reads like dystopian technology, now I look at it) and BAM! No more life...
    • Cake the phone with mud except the camera lens and remain perfectly still and quiet.

  • Assuming... (Score:5, Informative)

    by Hans Lehmann ( 571625 ) on Wednesday May 29, 2024 @07:35AM (#64507303)
    Assuming the lost person is carrying a cell phone that's turned on and hasn't already drained its battery. As I understand it, a cell phone battery will drain faster when there is no cell service since the phone will increase the transmitted power in order to try to make a connection.
    • This is a legitimate concern. In many cases search and rescue only gets started when someone doesn't show up for a considerable period of time, or when an emergency alert comes in, and often the latter in the form of an EPIRB already transmits the location of the lost. If someone is prepared enough they will often carry an personal locator beacon for this purpose. If they aren't prepared enough, they are usually the type of tourists taking selfies numbnuts doing stupid shit and are very likely to be sitting

  • by TerraFrost ( 611855 ) on Wednesday May 29, 2024 @08:10AM (#64507367)

    Roaming when there aren't any cell phone towers anywhere around is battery intensive. When I'm doing back country hikes, even without roaming I'm already probably putting excessive demands on the battery by using AllTrails for GPS Navigation and taking pictures and what not, battery life is quite the concern. Consequently, I usually put my phone into airplane mode when I'm hiking in the backcountry so that it's not constantly roaming for no point at all. Seems like that'll undermine the effectiveness of this new tech.

    I mean, I usually bring extra charges for my cellphone but those are of little benefit if there's water involved, due to either rain or just because I'm wading in the water (eg. The Narrows, be it the Texas Narrows or the Zion Narrows). Even tho the phones are waterproof the batteries usually aren't and if water gets into the USB-C connection you'll get a "moisture detected" warning when you try to plug it in and it won't charge for several hours after that. And sure, there's wireless charging, which works better with MagSafe than not, but that's a trickle charge compared to being physically plugged in.

    • by rundgong ( 1575963 ) on Wednesday May 29, 2024 @11:17AM (#64507769)

      Surely you would turn it on if you get lost? Especially if you know this tech is available to search teams.

      Of course it won't help every time, but it seems like it will help in a lot of cases.

      • Surely you would turn it on if you get lost? Especially if you know this tech is available to search teams.

        For how long? The issue here is when to know someone is looking for you. Unless you trigger an emergency beacon it could actually be days before an agency starts to look. At what point do you turn your phone on, and how long do you expect it to last going in full tilt doing a search?

        The clever person may wait until they hear the sound of a plane or helicopter and turn their phone on then, but the clever person probably wouldn't be lost in the back country without a personal location beacon in the first plac

        • If this becomes a popular thing, we will probably get recommendations for how to best utilize it. Like "When your battery is getting low, turn it on for 5 minutes every hour, on the hour", and then the search teams would know this too.

          There would likely even be apps that help you do this in the most efficient manner.

          But it doesn't have to be perfect. It's worthwhile if it is useful in enough cases.

    • Roaming when there aren't any cell phone towers anywhere around is battery intensive. When I'm doing back country hikes, even without roaming I'm already probably putting excessive demands on the battery by using AllTrails for GPS Navigation and taking pictures and what not, battery life is quite the concern. Consequently, I usually put my phone into airplane mode when I'm hiking in the backcountry so that it's not constantly roaming for no point at all. Seems like that'll undermine the effectiveness of this new tech.

      Presumably this only gets deployed if you're way past due (ie lost/in trouble). And if that happens and you see the helicopter you'd probably take your phone out of airplane mode (especially if you heard about this tech).

      • If you presume someone is that clever then you can presume that the person is either not lost or is carrying a satellite messenger or locator beacon, either of which cost less than a pair of hiking boots.

        A lot of the people who get rescued are not that clever. I very much doubt anyone will have heard about this tech and not already be prepared enough to contact emergency services when lost without it.

        The use case for this will be a very lucky edge case.

        • You never heard about the clever ones that watched Man vs Wild and navigated their way to safety (surviving on bugs and piss)
          • You never heard about the clever ones that watched Man vs Wild and navigated their way to safety (surviving on bugs and piss)

            and pitas [reddit.com].

            Note, there were actual survival shows in that era [wikipedia.org] where the presenter actually survived off the land (and lost lots of weight in the process).

        • If you presume someone is that clever then you can presume that the person is either not lost or is carrying a satellite messenger or locator beacon, either of which cost less than a pair of hiking boots.

          A lot of the people who get rescued are not that clever. I very much doubt anyone will have heard about this tech and not already be prepared enough to contact emergency services when lost without it.

          The use case for this will be a very lucky edge case.

          I don't know, I think there's quite a bit of space between hardcore back country hiker and moron who doesn't think to turn off their phone when they have no signal and the battery is low.

  • Isn't this similar to an FBI Stingray?

  • Portable Cell Towers have existed for a while, *ahem* Stingray.
    Definitely a better use of the technology, but it's been around for a while.

  • Governments for years have already been spoofing cell towers in order to intercept phone calls and text messages of anyone they deem to be a threat. The next phase of this technology is to integrate that fake cell tower onto a drone so that it is mobile, then use that same drone to track down the location of their enemies (e.g. the Julian Assanges, Edward Snowdens, Alex Jones, etc) and then finally blow them up like we've seen already happen with tiny inexpensive explosive laden drones in Ukraine. The fin
  • by Misagon ( 1135 ) on Wednesday May 29, 2024 @08:42AM (#64507429)

    I'd think that people going hiking in the "backcountry" would have already turned off their cell phones because they couldn't get reception.

    For some people, being cut off from cell phone reception is the point of going there in the first place.

    • Lost (Score:4, Insightful)

      by JBMcB ( 73720 ) on Wednesday May 29, 2024 @11:10AM (#64507755)

      Sure, but the first thing you do if you're lost in the wilderness is turn your phone on to see if you can call someone.

      • And when you can't call someone you either turn it off again or have your battery go flat a few hours later. The issue here is there needs to be a lucky overlap between a) search and rescue being near you, b) your phone being on, and c) your phone working. It'll be an edge case. And the people prepared enough to make it happen, i.e. those who know about the tech and thing about when hearing a helicopter to turn their phone on, are likely smart enough to not go out in the back country without some form of lo

        • by ceoyoyo ( 59147 )

          Satellite messagers cost a couple hundred dollars and have a montly fee. They are not "less than the cost of hiking boots." Well, maybe the diamond encrusted hiking boots people who get lost buy.

  • by clifwlkr ( 614327 ) on Wednesday May 29, 2024 @09:19AM (#64507495)
    Isn't this product about to be obsolete when Starlink enables their cell phone support? They've already demonstrated it and it is set to turn on this fall, which means every phone that supports those frequencies would have basic coverage over the entire world. I guess they better hurry up and sell a bunch of those units now. Having done SAR for 13 years, it seems doubtful that by the time we go and look for them their battery will still have charge and the phone will just be on. Batteries don't last that long when they are constantly looking for a cell signal.
    • I haven't done SAR but have done other first responder things of various flavors. This was my first thought, too - their battery will be dead. They will have left their mobile in the car at the trail head. Honestly if you know there's no reception why are you carrying it , unless you want books or whatever, which I could see..but then one would think it would be in airplane mode so that it doesn't drain the battery. I may be assigning too much tech knowledge to the mythical hiker, though.
      • why are you carrying it

        It's the only GPS some people have. Perfectly useful with downloaded maps.

        I get called "boomer" all the time when people see me hiking with my Garmin Etrex. Hate to think of the names they'd use when I whip out my Brunton.

        • Hey, I carry an inreach device with a gps in it. They may call you a boomer, but the battery life on my inreach running is many days (like five days), while the phone running maps is going to be lucky to make it through a day. Never mind the inreach can be dumpled into a river and come out working. I won't even begin to get into the rugged factor.

          That said I do carry my phone for pictures a lot of times, but I sure don't depend on it for life saving or route finding. They will learn the first time they
  • Some sort of dead mans switch that turns off airplane mode

  • "Lifeseeker" sounds a lot better than "DissidentSmasher" or any number of labels for the inevitable abuses. Reminds me of "Patriot Act".

    • Oh LifeSeeker sounds pretty terrifying as it is, considering how the "justice" system "seeks" the death penalty.
      (I will use justice with air quotes until Q/A Immunity is recognized as "unconstitutional", as stupidly ironic as it sounds)
  • If you are rich and need to be rescued for doing stupid shit, you should have your rich taken away.

  • Right here [wikipedia.org].

  • The corollary: if you did not bring your cellphone or its out of battery, you do not exist.

  • New Tech May Help Find Missing Cellphones In the Backcountry Within Minutes

    I am not saying the technology will not be useful. In many cases it will be. But this depends on the person, (a) having the phone on them at the time, (b) charged and turned on, (c) not being in 'airplane mode' or something similar.

    And all these are true, and the person is conscious, they might have one of the recent models that has "satellite sos" feature, which does the same thing from their end. so add (d) they have an older phone

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