Car GPS: Buying Guide

Global Positioning Systems (GPS) for cars are becoming increasingly popular, promising to take the stress out of navigating to an unknown destination. But the technology has some general limitations you need to be aware of before you buy one.

The systems rely on receiving satellite signals. No satellite signal, no guidance. Car navigation doesn’t work when you’re in an underground car park or tunnel. And even high-rise buildings in a city centre can block the view of the sky to an extent that leaves navigation systems lost or at least handicapped.

The systems can only be as good as the mapping data allows. Most of the models currently available in Australia use the same data, which still has weaknesses in coverage and points of interest — especially in regional and rural areas.

Don’t blindly trust your navigation system. The mapping data gets updated only once a year. So it won’t know about any road changes that happen between updates. And there may be traffic situations that are simply too tricky to handle for a navigation system — for example, if some quick lane-change manoeuvres are required.

Some car GPS models have a ‘walking’ option that lets you plot a pedestrian route ignoring one-way streets and using, for example, walkways through parks. However, none of them is suitable for guiding you on bushwalks.

So car GPS can be useful, but it definitely has limitations (and frustrations). Before you rush out and buy one, think carefully about whether it’ll really be worth it: how often do you usually have to use a street directory or map, and where are you likely to use it?

A car navigation system consists of:

• A Global Positioning System (GPS) receiver that picks up satellite signals that allow it to determine your exact position.
• A map database which includes a large number of ‘points of interest’, such as schools, police stations, car parks, petrol stations and hospitals.
• A computer processor to calculate routes, distances and times.
• A screen displaying maps and route instructions.
• A loudspeaker for verbal instructions.

You enter where you want to go. Using the map data, it then plots a route, calculates the travel distance and estimated time of arrival, and displays the route on a map. You can usually choose between the fastest or the shortest (geographically) route, or specifically exclude toll roads or highways.

Using satellite signals, it keeps track of your position and guides you along the plotted route with instructions on the display and verbally via a pre-recorded or computer-generated voice.

Portable units have a mount with a suction cap that can be attached to the windscreen. They plug into the cigarette lighter, but also have a battery that provides a few hours of operation. They’re installed within moments, and can therefore easily be moved from car to car.

Related:

• How to Select a GPS Car Navigation System (1)
• In-dash Car DVD buying guide (2)