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The use of GPS devices and smartphones as navigation aids

Over the last decade, the use of GPS (Global Positioning System) devices has become common to aid navigation on the hills, whilst over the last couple of years many Smartphones equipped with GPS technology have been used for the same purpose. This article aims to answer some of the common questions and dispel some of the myths around their use.

How do they work?
Both stand-alone GPS devices, and smartphones with GPS technology, work by detecting the position and signals from a series of satellites set up by the US military. The devices calculate their position by reference to these satellites.

What do they actually do?
There are a range of GPS devices and smartphone apps that have widely different functionality. At the more basic end, the GPS device or app may give you your current grid reference so you can then use this to help to navigate with your paper map. Many devices will let you pre-plot a route using mapping software on your PC (such as Memory Map etc.), or download a prepared route from elsewhere. The line of the pre-planned route is then often shown on the screen. At the top of the range are GPS devices such as Satmap or Garmin Oregon, and smartphone apps such as Viewranger and several others, that allow you to purchase full Ordnance Survey maps (1:25 000 or 1:50 000) which are then stored so they can be shown on your device (overlaid with any pre-planned route), with your current position marked.

Do you need a mobile phone signal for GPS to work on smartphones?
No. There is some confusion in that, if a mobile signal is available to them, Smartphones may use something called Assisted GPS to gain the approximate location from the phone signal. The mobile signal is then used to speed up the calculation of the position fix from the GPS satellites. The availability of a phone signal has no effect on the eventual accuracy of GPS readings once a device has fixed its position; the purpose is simply to get a fix faster when the GPS functionality is switched on. There are some cheap apps that do require an internet signal to show mapping, and so are not likely to work in wild areas. However, the better quality smartphone apps store any mapping legally on your phone so that it is always available.

How accurate are GPS devices?
The original generation of GPS devices gave an accuracy of around 15m, and often could not get a fix in narrow valleys or where there was forestry cover. More recent devices and smartphones tend to now use High Sensitivity GPS which is much more effective in forestry, and can be accurate to around 4m once the device has completed a fix. Occasionally GPS signals are jammed by the military. We are often informed of when this is scheduled to happen and include a news story on Walkhighlands if the jamming is likely to affect hillwalkers, though there are also GPS jamming exercises which are not announced.

Does this mean I no longer need a map and compass, or need to know how to read one?
No! Everyone heading into the hills needs to learn how to read a map, and to be able to navigate effectively with a paper map and compass.

Why? Firstly, even if you have a smartphone or GPS with full detailed OS mapping, it can't read and interpret the map for you! All it can do is show your position - being able to actually interpret the map correctly remains an essential skill. Heading into the hills means you need to be able to understand from the map what the terrain will be like, choose suitable routes from it and be able to make decisions around changing your route if you need to. For example, in the winter, there may be an dangerous cornice where a summer route runs close to the edge of the cliffs above a corrie; you need to be a skilled navigator here to be able to understand that you may need to take a route further back from the edge than the shown summer route, to avoid the risk of falling through the cornice. A smartphone, gps, or indeed a paper map cannot tell you this - its the skills of the map reader that are needed. Plans may also change; the weather may close in; heavy rain might mean that a burn won't be crossable; there may be an accident; so everyone needs to be able to look at the map and work out the best way to adjust any route to deal with changing situations.

Secondly, even if you are a skilled navigator who can read a map well, and are happy using a smartphone or gps to navigate, a paper map and compass should still be carried at the very least as a backup. Batteries could run down; although you can carry spares or a charger, there is still a chance your phone or gps could break or malfunction. So it's essential to at least have a paper map and compass as a reserve.

As mentioned above, even a smartphone/gps user navigating effectively should be using their map reading skills at all times. However, if using a smartphone or gps as your primary means of navigation, your compass skills could become rusty. If this applies to you, it's a good idea to practice regularly to ensure you can remember how to use a compass effectively if and when the need arises.

What about batteries? How long do they last?
This varies greatly. Generally, dedicated GPS devices have had longer battery life than smartphones. With smartphones it also depends on what other apps you are running, and what calls etc. you make. You can conserve battery further by switching off the mobile signal. Some smartphones can be switched on, recording a gps track for up to 14 hours or so; others may drain much, much faster. When buying a smartphone, it's worth checking the battery capacity; also, a larger screen is likely to drain the battery faster. With many models it is also possible to get a spare battery, or to carry a portable charging device (that effectively contains another battery). If using a smartphone or gps navigation, take the time to learn how to use it well and understand how it works and its limitations.

What about the device getting wet?
Most dedicated GPS devices are of rugged construction and are reasonably waterproof. Smartphones can be much more fragile, though waterproof cases are available and they can be used with care. Some smartphones are 'rugged' models which may be waterproof and better able to stand up to knocks - probably a good choice for those wanting to take them into the outdoors.

I keep hearing that smartphones and gps are increasing call-outs for Mountain Rescue as more walkers get lost. Why is this?

The root cause of getting lost is usually a lack of adequate navigation skills, no matter what technology is being used. In many cases, walkers do not have the skills to read a map or navigate effectively. Some mistakenly think that carrying a smartphone or gps means that they do not need these skills, which is a recipe for disaster, for all the reasons given above.

Every hill and mountain walker needs to learn how to interpret a map, and to navigate effectively using a map and compass, including in poor visibility. Check out the 'Navigator's Dozen' section for more information on these essential skills; skills such as Estimating Distance really do require practice! For those less sure of their abilities, there are excellent courses available on basic navigation, including at a low cost through the Mountaineering Scotland.

In other cases, walkers know how to navigate effectively using detailed mapping on their smartphone or gps, but they have not also taken a paper map and compass. They then get into difficulties when, for whatever reason, there is a problem with their device, as they have no backup.

This page by Walkhighlands; content approved by Mountaineering Scotland.