Buying guide: GPS units and sat navs

Need help shopping for a GPS unit? Deciding between sat navs from Garmin, TomTom and Navman? Read our handy buying guide

GPS stands for Global Positioning System. The system is made up of more than two dozen satellites that orbit the Earth. A GPS receiver can use these satellites to pinpoint your location, usually to an accuracy of 10m or better.

While there are many commercial, military and civilian uses for GPS, by far the most common is in-car navigation. In-car GPS units are a combination of a GPS receiver and a small computer that includes street maps. The in-car GPS unit can determine your position from the satellites and show you that location on the map.

From the GPS unit you can enter the location that you want to drive to and the unit will navigate you to it. Because the GPS unit constantly tracks your location, it can provide precise instructions on where and when to turn. And if you make a wrong turn, the GPS unit can recalculate the best way to get to the destination.

In addition, in-car GPS receivers can display a range of valuable information like your current speed and direction, altitude, the estimated time of arrival and even traffic and weather details. Most can even tell you the location of traffic "black spots", fixed speed cameras and red light cameras.

GPS receivers are now also a common feature of smartphones. A smartphone with a built-in GPS receiver usually ships with dedicated GPS mapping software. There is also a wide range of external Bluetooth GPS receivers, which can turn any Bluetooth-capable mobile phone into a fully fledged GPS device.

Other GPS receivers are available for specialist requirements such as boating and hiking. Boating GPS units include features useful on water, such as a man overboard function that instantly marks the location where a person has fallen overboard, while handheld GPS units are used by hikers and climbers to determine their position and prevent getting lost in isolated areas.

Why do I need an in-car GPS?

An in-car GPS unit is ideal for anyone who travels a lot or has a poor sense of direction. They eliminate the need for a street directory and are very handy in a number of situations. If you are a regular driver and often travel to unknown areas, a GPS unit can save you a lot of time. GPS units are also ideal for salespeople, delivery drivers, travellers, tourists, busy families, but most of all, anyone wanting the convenience of turn-by-turn directions.

Once you turn them on, and select a route, an in-car GPS will interact directly with you using voice guidance; for example, "in 100 metres, turn left". In addition to voice guidance, the GPS will show your current location on a map, making it easy to see exactly where you are.

Are there different types of in-car GPS units?

There are generally two types of in-car units. Some GPS units are integrated into a car's dashboard and are combined with your sound system, while portable units can be taken from car to car and are usually attached to your windscreen with a suction cap holder. Portable units are ideal if you want to have the convenience of GPS navigation in multiple cars, as it can be shared around a family. They are easily transportable and quite compact, and are usually charged via a cable running from your car cigarette lighter.

How do the maps work?

Each GPS unit uses mapping software and these maps are either loaded onto the unit before you purchase it, or are included on a memory card that slots into the unit. Some GPS units come with maps for multiple countries, while others just feature Australian maps. Most GPS units allow you to purchase extra maps; this is handy if, for example, you are going overseas and would like to use your GPS during your travels.

Generally, each different GPS manufacturer partners with a company that produces digital maps. Digital maps have a clear advantage over a street directory as they can be updated to accommodate any changes in roads. They also provide a large range of information that cannot be easily included in a street directory such as traffic signs, vehicle restrictions, post codes, house number ranges, points of interest, tourist information, and speed camera data.

Routes can be calculated via either the fastest or the shortest route. You can even tell your GPS to avoid things such as toll roads and highways. A GPS calculates the best route according to your specifications and displays it on the map. The map is typically a 3D view, although you can usually select from 2D, 3D and aerial views.

How often do I have to update my GPS maps?

Generally, new mapping data is released up to four times a year, and this usually incurs a charge. New maps are either purchased as an SD card, or can be downloaded onto the unit itself from the Internet.

How do you operate a GPS?

Current portable GPS units on the market have touch screens. Simply tap the text or buttons on the screen. The most common user operation for a GPS is to enter the address of your destination — this is done using the touch screen, by following a series of menus and entering information on the touch screen keyboard.

I have trouble reading maps. Will I still be able to use a GPS?

Most of the newer GPS maps offer a number of views, including 2D and 3D modes, so they are ideal for everyone. But most importantly, using an in-car GPS means you won’t have to look at the screen very often, as you’ll mainly be listening to voice guidance.

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