10

There are quite a lot of questions concerning GPS device usage, however I couldn't find any specific information on more passive usage (as in waiting for rescue).

Say I have a watch and a phone which both have inbuilt Global Positioning Systems (GPS). When I am stranded in the wilderness, what can I do with them, in order to use them in a most optimal way.

By this I mean, while i'm waiting for search and rescue... for the sake of argument say I cannot use those devices as the actual means of finding my way out, because of some environmental/physical impossibility.

Here are some points which I am interested in, but do not limit your answer to them:

  • Should the device be switched on?
  • Should the GPS on the device be switched on?
  • What can I do to prolong battery life?
  • Is the device useless once the battery is dead?
  • If I know they are looking for me, would they pick up the signal, if I switch it on for short periods every now and again?
  • Is it best if I stay in one place (environment permitting) and would it be harder for them if I am on the move?
21

If you're not using the device to find your way, it is useless as far as the GPS functionality is concerned, no matter whether it's switched on or off.

If I know they are looking for me, would they pick up the signal, if I switch it on for short periods every now and again?

What signal? The GPS signal is sent by satellites, GPS devices receive this signal, they don't send out anything. A phone might send out a GSM/UMTS/LTE/whatever signal when trying to contact a base station, but that has nothing to do with GPS, and I'm not sure whether rescue services can use those signals to detect a phone; typically they use information from the base station to find the location of phones, but in your situation there would not be a base station in reach.

  • 3
    All true. The exception though would be a GPS locator beacon if you had one. – user2766 Apr 23 '15 at 8:45
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    In the UK there is a system available to Mountain Rescue Teams called SARLOC which allows them to send a text to you with a link to a webpage. Clicking on this link opens a page in the phone's browser which queries the phone to identify its location as a Lat/Long coordinate. This location data is then displayed to the user and automatically added over the internet to the Mountain Rescue Team's database. The MRT call handler can then see the phone's (and hence the caller's) location displayed on a digital OS map display - using another application also developed by Ogwen Mountain Rescue Team. – Paul Lydon Apr 23 '15 at 11:27
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    @PaulLydon this sounds really good - shame the UK doesn't have 100% coverage! – Aravona Apr 23 '15 at 11:28
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    Isn't there an inherent contradiction between 'wilderness' and 'cell phone service'? Of course you could be stranded in non-wilderness areas, but I'm no longer amazed by people who venture into remote areas and expect to phone for help if the get in trouble. – jamesqf Apr 23 '15 at 19:38
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    @Mark (and others): My point is that the very availability of cell service removes an area from the (philosophical, rather than legal) category of 'wilderness'. I've likewise known people to get cell signals on peaks/ridges in legally-designated wilderness areas, and spend a lot of time in non-wilderness (northern Nevada/northeastern California) where there's no cell signal due to canyons, intervening mountains, or just not enough people around for anyone to bother putting up a cell tower. – jamesqf Apr 24 '15 at 20:10
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Use the GPS to determine your position and then text or email that to your rescuers. That will be the end of the GPS's contribution to the rescue process.

Staying put is generally best (saves your energy and ensures you don't move into an area they have searched and think you are not in) but that place should be safe and you should be discoverable in it. Ideally you would find that place and then send your co-ordinates.

  • Umm, assuming you have network coverage right? – Ricketyship Apr 28 '15 at 13:17
  • Yup: without that then it has no role at all if you don't intend to use it to figure out how to exit the situation yourself, a condition stipulated in the question. – Kate Gregory Apr 28 '15 at 13:18
  • I couldn't see network coverage point in the question. However, since the OP refers to "waiting for rescue" and "cannot use devices as means of finding my way out", forced to believe he/she has network coverage. – Ricketyship Apr 28 '15 at 13:22
3

Two scenarios are to be explored.

  • Do you have mobile coverage? Yes?

Then just find out your gps coordinates, send them to your rescuer. And stay put. In case your location changes, resend them (sounds lame but essential). Since you are asking about battery life, it's okay to switch off your GPS (given the device[mobile/watch] provides that option) to save your battery(assuming you have passed on the coordinates already). Also, keep your mobile network on to contact the rescuer (again, sounds lame, but essential).

  • No mobile coverage?

Your best bet is to use the GPS to find your way out. GPS only shows where you are located on earth. It doesn't give you any more information. In case you are using a mobile, there are apps(ex: maps.me) which allow you to have offline maps which can be used in mobile network-less regions (these maps need to be downloaded upfront using mobile network). In this case, you'll have to use this information to navigate out of your situation using the GPS. (GPS does not require mobile connectivity). Also, note that GPS does consume your battery based on the update interval. It's best to switch off your mobile network (since you have it not anyway) so that your device doesn't keep on searching for a network(which eats up your battery) and navigate out.

The reason I've added this answer is because there's an inherent assumption that mobile coverage is present in one or two of the answers and the comments provided for the same.

Another point to be noted. In case you are waiting for rescue and have no mobile coverage, GPS has zero value. You might as well switch the whole thing off :P

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Always mark or keep track of your starting point co-ords, or finish co-ord. Turn off the unit to save power and check once in a while to see if # are getting closer, you will find out fast if you are headed in the right direction. #'s will get closer. Play with it in your backyard and learn the capabilities of these new machines, awesome!!! Never rely on this tech though, learn the old fashion way first. They sure can help you to learn how to use a compass and topo map though!!

-2

Take the batteries out and use them to start fires. You won't even need to encode your lat/lon in smoke signals, that feature is built in.


follow up (edited again - note that the question does not say the person is lost, just trying to get rescued) My answer sounds flippant, but seriously, if you can't move or send info out, it's useless. Maybe MacGyver could turn the GPS into a transmitter, but can you? You can use the batteries & wires to makes sparks, or maybe use the screen as a signaling mirror. Or, if it has an illuminated screen, use that as a signal at night. Other than that, your GPS is as useful as a brick.

  • I'm not sure that batteries burn all that well :-) Or did you mean use them with a piece of wire to make sparks? – jamesqf Apr 26 '15 at 18:22
  • Your follow up even contains useful (and funny) ideas, still this is not an answer to the question. This could be a commentary, but not worth a ful answer (outdoors.stackexchange.com/help/how-to-answer). – imsodin Apr 28 '15 at 7:17
  • The question asked about using GPS when stranded, and implies that the victim can not travel. It does not say that the victim is lost. He/she is merely stuck in a place where no one else can find him. So the focus of the question seems to be on using GPS to aid the rescue. The other answers depend on having phone service, which make the whole thing moot. So I would argue that the nobody has found an actual use for the GPS device by itself. – Pepi Apr 28 '15 at 7:47

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