First designed as part of a military system for navigating on the ground, above the earth are 24 functioning satellites that circulate, allowing everyone to pick up signals. 

This system of satellites is known as the Global Positioning System (GPS) and the machine or device we use to take their information is known as a ‘GPS receiver’, or a Sat-Nav (Satellite Navigation Device).

The satellite manages to locate a receiver via a soundless signal, which is unique to each satellite. Through this signal, the receiver can determine its orbital position via it’s own distance from each signal point. This distance is then calculated, allowing the receiver to provide a very accurate sign of where it’s based. This then feeds back to the user, so you can see where you are, and calculate your way to another destination. 

The positives of a GPS or a Sat Nav:

• Safety – You can be found, or find your way in any area.
• Convenience- Sat Navs can be used on foot, in the car, and can be taken anywhere, especially if they are protected from abrassion
• Interactivity- Many GPS devices allow you to download routes, interact with their devices and users play games and access information
• Personalisation – add your own routes, store maps and check your latest stats, from your speed to your distance to your average height above sea level.

The negatives of a GPS are as follows:

• The expense, when compared with a simple compass and a map
• The technology, which is still not 100% accurate, and has a 10 metre margin of error when defining your location.
• Standard GPS systems with no electronic compass have no ability to sense movement, which can make calculating difficult

• 150g – 200g is a good size for a handheld, un mounted GPS system.
• Remember that batteries add around 30g of weight, so check that the system is weighed with or without batteries before you purchase.

• The visuals on the screen can vary from full colour, or visuals shown as a dotted line along the screen in black as seen in the image of the Garmin device above. 
• Whether in colour or black, the resolution of the screen’s visuals is measured in ‘pixels’ and 160 x 240 pixels would be standard for a colour screen version.
• The pixel size of images are in line with the screem size, so 2.5 inches plus is an ideal size for good vision and easy handling. Larger sizes are more expensive, but can provide better visuals.
• Look out for a Transflective colour touchscreen - TFT if you do choose a colour based device. This allows colours to retain their brightness, without having the sun’s glare on the screen, ideal for summer days.
• Most screens are simple to use touch screen styles, so remember to familiarize yourself with your system before you hit the road.

• Look for a good strong battery life so you won’t need to recharge en route.
• Most GPS can be charger either via a 12v system, such as an in car charger, or for handheld devices, AA batteries are common.
• 20 hours of run time is ideal for a colour screen system.
• Consider the more expensive lithium batteries in your system, this will help it to run for longer.

• With GPS systems you can now download memory maps, which can help keep you on track at 1:50, 000 or 1:25,000 scales. With various memory maps, from AA guides to Ordnance Survey routes, to particular detailed routes on destinations, you can pinpoint a great tour of a small local area.
• Check if your GPS system accepts data cards, usually defined by having a ‘ microSD™ card slot’ – to insert the card into, or a microSD™ card itself.
• A microSD card allows extra memory so you can download more functions such as maps and other accessories for your GPS system.
• Some GPS have preloaded maps already set up, so check first what you get with each GPS system.
• Some may contain street maps, others need to be set up via a PC or laptop first.
• Look for the built-in memory and match this with the maps you intend to download to your devise. 850 MB is a standard GPS systems stored memory. Extra functions such as internal electronic compasses and games may require more of this memory.
• Check how many locations and routes you can save on your GPS, a handy function for regular users.

• As well as sharing info, by connecting your GPS you can tell you how far and how fast you've travelled, great for fitness and goal setting.
• Unit-to-unit transfer means that your GPS system shares data wirelessly with similar units, handy for providing follow adventures with your preferred route or set locations.
• Look for Location Saving Function – and check how many key routes your chosen device can hold.

• Look for a case or consider buying an additional case to help protect you GPS from knocks, bumps and abrasion.
• As well as the cases, check if your GPS comes with any additional webbing that protects it from knocks and bumps

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• WAAS-enabled GPS receiver: (WAAS) is a technology found in many arecreational GPS systems. WAAS stands for Wide Area Augmentation System and is a way of increasing your GPS receivers accuracy. With a usually 10 metre area of doubt in a GPS’s geographical calculations, WAAD can reduce this to just 1 and a half meters. Developed initially for aircraft, this is a space based system that is available globally. WAAS is a great extra for a GPS system, however, being air based it encounters some of the same problems as satellite systems, where overhead cover, such as forest canopy and dense overhead obstacles cause intereference with the device.

• GeoCaching: A game inspired by the leaps and bounds in recent technology, the purpose of Geocaching is to locate hidden treasure – physically placed there by fellow GeoCachers. The treasure, known as a geocache, is located via a GPS device. There are over 900,000 areas available to get involved with. Go to www.geocaching.com to learn more.

• ‘Track Back ‘ –allows you to trace back your path and reverses it so you can easily get hone.

• Waterproofing functions come as standard with most GPS systems, but check first before you take it out on an adventure.

• Automatic routing (turn by turn routing on roads):
• ‘Barometric altimeter’. This uses pressure from the atmosphere to define your distance above sea level. This can help determine your location in areas of high altitude. Able to work at heights via the sea, whilst standard GPS technology helps pinpoint you via satellites, you get a very accurate ‘reading’ of your whereabouts, ideal if you’re on the move on a mountain top.
• An Electric Compass is a fantastic inbuilt accessory if you need a GPS for the great outdoors. Whilst GPS satellites help provide accurate – to around 10 metres- information on your whereabouts geographically, it doesn’t have the inbuilt knowledge of motion in terms of direction. This means back stepping, wheeling you bike in reverse and general human movement can throw the GPS off. Unless it has an electric compass which will move when you do, so you can trust that ‘Head south’ means just that.
• Games- As you would imagine, on the go games ideal for some light relief. Less Call of Duty and more call of the simplistic, you can while away a few hours catching virtual lizards or matching pairs. You won’t win anything, sadly, and your battery life may suffer as a result, so keep this as a last resort for boredom.
• Sun and Moon Rise/Set Information: Ideal for you if you want to be at a certain destination in time for a particularly spectacular sunrise. Similarly many GPS devices also contain information on tide times as well as details on the best times and areas to Hunt and Fish.

   

• Allow a 1 – 10 metre ‘margin of erroror’ in GPS Systems. Designed to be accurate as possible, this can still be slightly off when the signal is hindered, either by large objects, thick forests or radio signals.

  Make sure that you take a whistle and safety equipment with you too, a GPS is only an aid to navigation and cannot help if you are injured or need to attract attention.

   

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