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The Which? guide to buying the best sat nav

What is a sat nav?

Whether you want to take a Sunday drive, or travel across the continent, an in-car satellite navigation system (sat nav) can help make your journey from A to B effortless, and get you to your destination in good time.

Using global positioning system (GPS) signals, sat nav devices can locate your position, give you a choice of routes to your destination, inform you about traffic jams and other useful things.

There’s no shortage of models to choose from. Should you buy a TomTom or Garmin sat nav, or one from another brand? Do you need live traffic updates or Google Search? Will you be driving solely in the UK, or will you need mapping for other countries? Would you be better off with a sat nav app for your phone? This guide will help you pick the right sat nav for you, and if you watch the video above, you'll find out what makes a Which? Best Buy.

Should I buy TomTom or Garmin?

The two biggest names in the sat nav world are TomTom and Garmin, both of which offer plenty of choice. TomTom’s Start and Garmin’s Essential ranges contain each brand’s entry-level models. These are fine if you just want an easy-to-use sat nav to get you from A to B, but you won’t find advanced features like live traffic data or internet features here.

At the other end of the scale are TomTom’s Go and Garmin’s Premium ranges. These are stuffed to the gills with features such as traffic information, real-time photo images of upcoming junctions, Twitter compatibility and Google Search. If you spend a lot of time on the road, these extra functions could well appeal.

Whether you decide to opt for a sat nav made by TomTom, Garmin or another brand will come down to personal preferences about functionality and the user interface. Try each model out in-store first to see which you find easiest to operate.

Do I need traffic services?

If you’ve ever been stuck in a traffic jam with no end in sight, you’ll really appreciate the traffic avoidance features of sat navs. These collate road information from a variety of sources and identify problem areas as they appear, and then suggest routes around them.

You’ll find that the more expensive models include traffic services as standard. These can represent good value in the long run for regular drivers, as although you can purchase traffic subscriptions separately, this can be an expensive way to access the information.

What sort of mapping do I need?

As a rule, mapping for sat navs is split into three different types: UK & ROI, Europe and Worldwide. If you intend to drive just within the UK, don’t be tempted to pay more for European and Worldwide maps that you may never use. If you do purchase a UK & ROI sat nav, and later decide that you would like to drive on the Continent, you’ll still be able to pay to download the extra maps.

When you get your sat nav home, be sure to update it. Most manufacturers offer a free map update when you first purchase your sat nav, so you can be certain that you’re driving with the very latest maps.

What screen size should I have?

Sat navs come in a range of sizes. Consider what size screen you would find most comfortable before you buy, visiting a store to see different sat navs in action if necessary.

A good sat nav screen should be clear and bright, viewable at an angle and readable even in direct sunlight. If you’re opting for a TomTom or Garmin model, these issues won’t be a concern, but keep in mind that for both of these brands, the screen resolution on the more expensive models will be sharper.

Should I consider sat nav apps?

As well as traditional stand-alone sat navs, there are now many apps available that can turn your mobile phone into a navigation device. From free alternatives from Google and Apple, to paid-for versions from established brands like TomTom and Garmin, sat nav apps are worth considering if you’re looking for a quicker and cheaper alternative to a stand-alone sat nav.