Global Positioning Systems (GPS)
GPS stands for Global Positioning System – a system of Earth-orbiting satellite which provides data to pinpoint your exact position on the globe when read by a GPS receiver. GPS units are currently accurate to within about 15 metres but WAAS-enabled (Wide Area Augmentation System, a US satellite network) and EGNOS-enabled (a European network) devices will become available to increase this accuracy down to 3-5 metres.
GPS receivers are a handy piece of kit to have as long as you remember that they are not a substitute for a map! That might seem obvious, but never leave home without your OS map and a compass. You don’t have to spend a fortune on a GPS receiver suitable for walkers/hikers. Like many gadgets, there are bells and whistles on offer, but you can get away with a simple entry level GPS receiver for your walks for under £100.
Features to look out for when buying a GPS device
Carrying a GPS receiver with you is a waste of time unless it works when it’s needed, so look for long battery life. Some receivers have rechargeable batteries.
Being able to read a GPS receiver in all weathers and light conditions is essential for walkers and hikers, and higher-priced models with large, clear colour screens make reading map detail easier. But if you can manage with a simple, black and white screen, then an entry level model will suffice.
The GPS receiver case should be robust, tough enough to take a few knocks, and preferably waterproof. Smartphones and PDAs are unlikely to be as durable or cope with the effects of weather.
Map datums describe the irregular shape of the Earth for a particular region and different maps have different map datums. Lines of latitude and longitude on a map or chart are referenced to a specific map datum. Every chart has a map datum reference, usually listed in the title block of the chart. If you are comparing GPS coordinates to a chart or map, the map datum in the GPS unit must be set to match the chart or map’s datum for accurate comparison. GPS users should reference their GPS receivers to their maps. In the UK the GPS receiver should be set to OSGB or GRB36. For most European countries the unit should be set to European 1950.
Waypoints are the coordinates of a location – the stop-off points, locations and landmarks worth storing on your GPS, to enable you to navigate back to these at a later date. You can also use a track back feature to re-trace your steps back to your car, or to your start point, or to reach it via another route. So a large built in memory is a must and look out for units with a slot for a memory card to store extra mapping.
A route is a series of waypoints that are entered in the way you want to navigate them.
GPS receivers come in several flavours – dedicated hand-held receivers, PDAs (personal digital assistants), Smartphones, and PNDs (portable navigation devices) that can be used in a car or on the hills. Dedicated outdoor systems are usually more robust and give longer battery life.
GPSs use a numbers of channels to track the satellites – the more channels the greater the accuracy, particularly in congested and wooded areas. 12 or 16 channel receivers are now common and are better than an 6 or 8 channel receivers.
Waypoints can be keyed in manually but it is time consuming, so software to do this for you is essential. Look out for waypoint upload/download capability using software like Memory-Map, Garmin Topo, Magellan Topo, Anquet, ViewRanger, MapyxQuo.
UK maps have a grid so you can identify a location using a grid reference. The commonest coordinate systems in the world are LAT/LON and UTM so if you are using a GPS receiver in the UK, the coordinate system needs setting to match the coordinate system on the maps you are using.
Digital Mapping Software
Digital mapping software enables you to view Ordnance Survey mapping on your computer. You can then download routes from your computer to a GPS and also upload tracklogs of where you walk. Some products also have 3D and aerial views. Having said that, you may not need OS mapping software, expecially on easy trails and well known mountain routes – a non-mapping unit will give you an accurate grid reference that you can transfer to a paper map. OS mapping can be expensive, it’s not easy to view on a small screen, and it eats up battery life. Your preference for map detail and your specific activities will determine whether you need OS mapping and which software is right for you. But if you do decide to buy mapping software, make sure that it’s compatible with your computer and don’t assume that the software you buy will work on any other devices you may have and that you can swap the mapping between one device and another. In most cases, you will not be able to do this, so check this out before buying.
Dedicated GPS Receivers
- Garmin eTrex H – £86 – Now only £79.99
- Garmin Vista HCx – £229 – With Free Delivery
- Garmin Oregon 300 – £350
- Magellan Triton 500 £270
- Magellan Triton 2000 £530
- Satmap Active 10 Plus £380 – Now only £299
- MWg Zinc II – £200 – on contract Free
- Nokia N79 – £275 – on contract £70
- Blackberry Bold 9000 £500 – on contract £137