Why buy a car GPS?

Our roads are well signposted and a good road map is much cheaper – although the GPS should sort out any in-car arguments about which route to take.

Maybe your work takes you to unfamiliar parts of our bigger cities. In that case a car GPS would be handy. Our experience is that they work best in cities.

For trips overseas it'd be cheaper to hire a car with GPS fitted rather than taking your own unit: overseas maps are usually expensive to add to a GPS. Either way, GPS would help make navigation easier in a strange country.

Just remember: the GPS is only ever as good as its map (see below).

Traps and tricks

• Check that your GPS unit is set to the "fastest" rather than the "shortest" route. In an earlier test with a unit on the shortest-route setting we travelled over a fairly rough rural gravel road. When we asked the unit to recalculate an alternative route, it came up with a forestry road with a locked gate! No doubt it's a paper road and in theory can be driven, which is why it's on the unit's map.
  
  Any GPS could take you on an unpredictable shorter route adventure like this. But some can be set to avoid gravel roads.
• Some units can be set to avoid toll roads – and even motorways.
• Roads are often re-routed, changed or blocked off at one end. If you can't find an address with your GPS, there may be two parts to the street with a gap in the middle.

GPS in your pocket

Nearly every smart phone now comes with a GPS map-and-directions function, usually as basic street-maps where the view is top-down (rather than in 3D) and not always oriented to the direction you’re facing. The instructions are clear – but they’re written (not spoken) and must be read by a passenger or when the car is stopped.

However, there are GPS apps you can buy for your phone – such as TomTom on the iPhone (see our 2010 test). You can also buy a windscreen mount for the phone.

Where to put it

The New Zealand Transport Authority (NZTA) allows a "TV screen" to be visible to the driver "for the purpose of navigation". However, your vehicle's windscreen must be "kept free of obstruction to allow sufficient view through it" so you can drive safely.

Where possible we placed the units just to the left of the steering wheel at the bottom of the windscreen – but you may have to adjust your unit depending on its charging cable location (some were awkwardly positioned).

Discourage thieves

Many people remove their GPS from the windscreen and put it in the glove box or under the seat when they reach their destination. The suction cup can leave circular rings on the windscreen, tipping off thieves that a GPS might be in the vehicle.

Even if you don't leave the GPS in the car, wiping the rings off can help avoid your car being broken into.