GPS receivers use different numbers of channels to track the satellites. The more channels a receiver has the more chance the unit will find the satellites and pinpoint your location.

Having external power capability is a nice feature if you using a GPS in the car and can save a lot of batteries. Does the unit fit a mobile charger or solar panel power unit?

Battery life
The more features a unit has the more battery power is required. On the hill you’ll have to relie on battery life so good battery life is important. And don’t forget some spares!

Large screens use more battery power but the larger the screen the more information it can display and the easier it is to read. A colour screen makes the map more readable but again uses more power than a greyscale screen (all the tested units here are colour). Screen quality also varies.

If the unit has buttons, are they easy to use? Can you still operate them with gloves on? Do they accidentally get pushed on in your pocket.

If you want to store lots of routes then you’ll need plenty of memory space for storing the waypoints (coordinates of a location). It’s useful to store various routes so you don’t have to reload routes all the time. Storing 10 routes is good but more capacity than that is better, especially for regular users.

Upload / download capacity
Keying in routes and waypoints is very slow so you’ll want to be able to a computer link to upload and download software.

Can the unit you choose be loaded with the maps you want? Not all GPS units can be loaded with European or international maps. Also consider the mapping scales, 1:25K show a lot more detail than 1:50K.

Does it have one and is it magnetic? A GPS unit with a digital magnetic compass will point you in the right direction before you start moving.

UK and International use
When taking these units abroad do they allow you to match up the coordinate systems to mapping system in other countries? The UK system is usually referred to as OSGB, ord srvy GB or British Grid.

Which GPS is right for you?
The best way to choose a GPS is to decide on the relative importance of each feature or function. Measure up the models within your budget against answers to the following questions:

•How many waypoints, routes and tracks will I need to store?
•Will I need removable memory for large areas of mapping?
•Will the electronic compass/barometric altimeter combo be useful?
•What’s the best sort of screen size/ resolution/brightness?
•Do I want audible alarms?
•What type of battery is used and how long is the battery life?
•How easy is it to use, especially wearing gloves?

Techy terms
•Waypoint: A GPS position expressed in the UK as an OS grid reference.
•Route: A number of GPS waypoints linked together in the order in which they are to be navigated.
•Track: A GPS record of movement across the ground while travelling on a specific journey.
•High sensitivity (aerial): This should receive a good satellite signal even in forests and gullies. It will often work even indoors.
•Topo mapping: A stripped-down OS-type map on the GPS screen showing contours, streams, many paths, roads and point of interest features. Current position, waypoints, routes and tracks can be seen as an overlay on this map.
•Internal memory: The number of waypoints, routes and tracks a GPS will store, plus fixed internal memory (MB) for mapping.
•Electronic compass: This will provide an accurate navigational direction pointer even when you’re stationery. Without this, you must be moving to get an accurate navigational direction.
•Barometric altimeter: This shows total ascent and descent, altitude and basic weather trends through changes in pressure.
•Screen shape: Portrait screens are higher than they are wide. This is useful so that you can see as much of the route ahead as possible. Landscape screens are wider than they are high.