To GPS or not to GPS during SHTF


GPS, Global Positioning System is a modern way of determine one’s position. It uses satellites, which are in orbit around the planet. By extreme accurate timings and something called triangulation it is possible to determine your location for about a meter accurate. In order to be able to communicate with these GPS satellites and to actually know where you are, you will need a GPS device with some kind of digital map installed on it. GPS devices are electronic devices, which are being used by a lot of people and organizations. Pilots use them in their aircraft, truck drivers use them and most everyday people use them for their convenience. I guess everyone knows Tomtom and Garmin. Two companies that are know of there navigation equipment. Let me talk about these kind of devices. The main question I want to answer is whether or not it is wise to add a GPS navigation device to your survival equipment or bug out bag.

Concerns with GPS devices are mainly: power consumption, size and weight, usefulness and whether or not the GPS service will be available around a SHTF situation. Let’s get more into these 4 concerns.

Power Consumption
All GPS devices I know of needs power and the vast majority have a built-in rechargeable lithium-ion or lithium-polymer battery, but there are models which runs on AA size standard batteries. The runtime per charge differs roughly differs between 90 minutes and a day. Most car model GPS navigation devices have bigger screens and are more optimized for road travel. Also car model GPS navigation devices tend to have lower run-time per battery charge and almost all of them have a built-in battery. The idea is that they are hooked up to the cigarette 12V outlet of the car when in use. A Tomtom start 20 is a example of a car navigation system. The hikers hand-held models of GPS navigation devices are in this power aspect a bit better: They offer better battery life and a lot of these models run on standard AA batteries. Which can be convenient in a SHTF scenario. Run times of 24 hours or more are not uncommon for these type of devices. For example the Garmin Etrex 30X is a device I’m talking about.
One thing is sure: You will need electrical power to be able to rely on GPS navigation. If you want to go with a navigation system with a built-in rechargeable battery, you will need something to charge it to bring along with it. Without any possibility to charge it, it will be an useless piece of hardware to you. A portable solar charger or a precharged power bank could be sufficient, depending your situation. On the other hand, if you decide to go with a standard AA battery powered device, you need to bring along additional batteries with you or rechargeable (NiMH) batteries and a charger, which is capable of charging on-the-go via solar power by example. The advantage of normal AA batteries over built-in recharchable Li-Ion/Li-Po batteries, where the latter are not easily replaced, depends on the situation you are in. If you tend to bug out or survive in a rural area, with almost no civilization close by, it might be more beneficial to go with the built-in battery and a portable solar panel along. In more urban areas it might be more convenient to go with AA batteries. There two reasons to this:
In rural areas you are more likely to get some sunlight on you and less likely to find batteries. In urban areas you are less likely to get some sunlight on you and more likely to find AA batteries somewhere.
What option you want to choose or not choose: You will need power, not much, but you will need it.

Size and Weight
A GPS navigation system weights about 100 to 200 grams and are as big as a wallet or mobile phone. Like how wallets can differ in size, so does GPS Navigation systems differ in size. And a mobile phone is because most mobile phones have GPS functionality. To my opinion and if I look at just the weight and size, it would be an essential piece of hardware to bring with me. Compasses are generally smaller, but I found out that a good compass, with mirror and adjustable ring, is about the same size as a small GPS navigation device, having only about twice or thrice the density (weighing more). I have them both in my bag, and it’s only a 35 liter backpack.

To be short: GPS navigation devices are useful. Time taken to navigate via map or compass or combined is slower and require more attention. Attention you want to have on your surroundings and not on your way of navigation. Unfolding and folding a big map takes relatively a lot of time, makes noise and tends to make you visible with all the moving you do in the process. A compass requires focus and you need to know where you actually are in order to know where you going to in order to navigate well with a compass. Also with a compass alone you will need in what direction it is where you need to go relative to your own position. This requires knowledge about your surroundings and skills using a compass. No doubt I would strongly advice to learn how to navigate with a compass and try it a few times, because a compass will most certainly work when you map is all torn up or blown away and your GPS navigation has no power any more or is broken. But as long you have access to your GPS navigation device and it has power and is still functioning, a map nor a compass will beat it in efficiency and ease of use. Depending on the model you will know instantly by a glance at the screen where you are and in what direction you will need to go (if any is set). This takes only a second of your attention. There are limitations you will need to take in consideration:
Indoor navigation might fail due to lack of connection to satellites, possible sound beeps, backlight of screen, whether or not waterproof and power. Power speaks for it self. Indoor navigation is something you need to be aware of. Dense roofs, like concrete roofings will block the satellite signals. This makes it impossible or hard to navigate while inside a building. Also it might take some seconds to reacquire satellite connections when you step outside again. Consider having a waterproof device, or put it in a zip-loc plastic bag. It will still work within the bag and while a little less convenient, it will still be possible to fully operate the device.
Take notice of any sound effects (beeps, talking) and the backlight brightness of the screen. In the night, you will draw a lot of attention from looters and bandits when you having the brightness maxed out. It also is bad for your own awareness, since your eyes need to adjust to the darkness around you after they got first immersed in the bright light of a maxed out backlight of the screen to second have to see in the dark of the night again. You won’t be able to see anything around you for seconds, while others will see you. You will also spare battery life with a more dim backlight. Sound effects you might want to turn off. A working navigation device might be very well wanted in your surroundings and giving away that you have one, or just giving away that you are actually around, might be a stupid thing to do. Keep it in your pocket if you are in areas where you don’t know if there are people who would possible kill you for your gear, food or by any other means.
Another thing to be aware of is the maps. Not all GPS devices that works with maps, has the whole world covered, or the part covered where you want to go to, or where you are. Make sure you have installed the map you might probably need during a SHTF. On a mobile phone you have to be very careful since some pre-loaded apps will download maps as-you-go. That means that the WiFi network or 3G/4G network is used to download map pieces around your position as you go around. When there is no WiFi and no mobile network, you will probably not be able to see the map, or only a small part. You might download and install a ‘real’ navigation app for that if you want to use a mobile phone. This before SHTF, of course.

Availability of GPS service
GPS works with satellites and those satellites are owned by someone or some organization. This is in this case the U.S. government. The D.O.D. (Department of Defense) is responsible for their operation and management. There are a few possible ways GPS might not be available to the general public and a few possible ways it might not be available at all. Let’s go through them:

-Satellites gets destroyed or disabled. This actually might happen in a full scale or global war. There are missiles available and owned by the bigger nations that can actually take out satellites from the ground or from high attitude aircraft. In this case no one will benefit from GPS signals any more. The system is just broken and the change that you will be able to use the GPS navigation device again very soon will be limited.

-D.O.D. or U.S. government decides to cut off general use of GPS. Yes, this is possible and it is called ‘Selective Availability’. Actually before the year 2000, GPS was limited for public use, which meant a great inaccuracy in navigation, artificially implanted for non-military or non-compliant GPS devices. This can be turned on again for any reason possible. The changes they will do this, are limited, since a lot of dependency has been built around GPS now the day. Making the system very inaccurate again on purpose, won’t be an easy choice. The GPS website states that Selective Availability won’t be ever turned on again. But that’s what they say when there is peace on U.S. soil. In a case where there is some kind of civil war when home brew GPS guided bombs are flying around, they might think and act different.
There is actually a limit for non-U.S. Military GPS devices in order to prevent states and people making GPS guided missiles somewhat. The attitude is maxed at 18 kilometer from ground and the speed is limited to 515 km/h. This is not really a limit on the satellite signals, actually, GPS provides beyond both the speed and attitude, still the same accuracy, but it might that the GPS navigation device itself has a restriction build-in. This is because the device is considered a ‘munition’ by U.S. law, if it’s allowed to operate beyond the given parameters speed and attitude. Since you are probably not moving that high or that fast during a SHTF, this would not be of your concern. Just make sure, that if you are planning to make any GPS guided missiles, that you keep in the bounds, or you might lose your missile prematurely due to unexpected results… You might want to check these 2 links about GPS:

-GPS drift
the GPS system works by timing, a very very accurate timing. Also the position of the satellites, also a very accurate position of the satellites. The satellites sends time data to the earth and does that repeatedly. The GPS navigation device globally knows where the satellites are. By comparing the timestamp received from a satellite to the own time from at least 3 satellites, where the position is know of, the GPS navigation device can pinpoint it’s own location. These satellites move in orbit around the planet, but their traject might me slow down or speed up or wobble a tiny tiny bit every hour or so. Also the internal clocks of the satellites may differ a bit over time compared to other satellites. This is caused by slightly different electronics and possible slight temperature differences, which can happen in space. This is phenomena of slightly changing parameters relative to each other is called drift. Normally this drift is compensated so now and then by contact via ground stations. The satellites will pass and align to a ground station on earth so now and then. This gives the ground station the opportunity to send precise location and time data to the satellite and back. The satellite replaces it’s own data with the new data if they don’t match and everything is fine and in pace. When those ground stations blow up due to actions of war, got taken, or stops working from whatever reason possible, there will be drift. In this case it will mean that the GPS navigation system gets slightly false data from the satellites and over time this error in data becomes bigger and bigger. In the end it means that GPS navigation becomes inaccurate. First off by a meter, then by 2 meter and before you know you off by 100 kilometers. When this starts to happen after loss of ground stations, I don’t know. But there are speculations that the usefulness of GPS start to perish after a few days to a few weeks after the satellites are not being updated any more. If your accuracy seems to ‘drift’ away over time, it might be well possible it’s due to the satellites are not being updated any more.

GPS is great; for so long it works. I don’t think the small size and weight are worth nagging about, since the convenience you get from it, is substantial. There is one major downside and that is power. GPS navigation devices are power hungry, in means of batteries or recharging an internal battery. If you already packing batteries or a solar charger or any means of electrical power with you, than adding a GPS device to it, is to me a no-brainer. Possible you will already, since you will bring your phone and possible some kind of radio or walkie talkie anyhow. Take in consideration that GPS works with satellites that are owned by the U.S. government. Depending on the SHTF situation, they can be destroyed by another nation, they can be turned off or vastly limited for public use by the U.S. itself or they can loose accuracy due to GPS drift which is caused by a broken connection to the ground stations. It’s because of all of this very advisable to bring also a map or compass (best is both) with you along with your GPS device. Also learn to navigate with the map and compass and you will be good to go.