What is GPS?

The Global Positioning System is a network of 24 satellites circling 17 742 kilometres above the Earth. Each carries a precise atomic clock and broadcasts its identity, location, and time. GPS locators – such as in a vehicle navigation system – use radio receivers, clocks, and small computers to provide your position. Originally developed by the U.S. Department of Defense, it was later made available for consumer use.

The U.S. Military continues to maintain the network so the satellite navigation-equipped amongst us can stay on track.

Using automotive satellite navigation is easy. Simply work out where you're going, touch some buttons and let your new mate do the work for you. It can act like a true local wherever you may venture. Petrol  stations, cafes, pubs and museums are just some of the points of interest your little navigator can direct you to.

There are basically two sorts of in-car navigation on the market; inbuilt and portable. Portable rely solely on the GPS (Global Positioning System), which means reception can fail or be greatly reduced in tunnels, tall buildings and valleys. Portable models are suitable for hire cars, leased cars or users with a stable of automobiles. Some have larger screens, others use touch screens and some are remote controlled.

In-built models rely on more than one source of positioning data. They use combined information from the GPS, a gyroscope and a vehicle speed sensor to provide driver directions more accurately. The displays are usually permanently installed, meaning they can also be used to display other images such as video sources, car system information and reverse-cameras.

There's a product to suit virtually everyone, even motorcyclists. Here are some of the best.

Blaupunkt – TravelPilot DX-V Price $3299 See www.blaupunkt.com.au

Once again, ‘Made in Germany', means quality. Blaupunkt's navigation systems are fitted into S-Class Mercedes, top-of the- range Volkswagens and Audis, and Blaupunkt claims to be the original brand of in-car navigation technology. The DX-V can also be retro-fitted to any car by qualified installers.

The TravelPilot DX-V's features shine bright. A removable widescreen monitor acts as a split screen, making it possible to simultaneously display arrow symbols and a map view. The large 6.5 inch colour LCD allows for direct changes to settings such as contrast, angle or brightness.

A recently-developed, easy-to-clean protective film makes the screen particularly resistant to reflection, and it is also easy to detach from its mount — which means you can take it with you, and deter those nasty car thieves. It displays simultaneous arrow/map and map alignments (north, automatic, zoom on junction) and combines exact spoken recommendations with visual directional information. Included is a brushless CD drive mechanism which is claimed to last for 10-15 years.

Blaupunkt's Jason Javaherian says "It comes complete with multiple CPU (Central Processing Unit) modules. Most other systems have only the one; ours have three which run simultaneously, so if one crashes, the other two continue working. The system uses not only GPS to navigate but also a vehicle speed sensor and a  gyroscope.

"You'll fi nd other brands, especially the portable ones, will only rely on a GPS signal. So when portable systems go into a tunnel or you are surrounded by tall buildings, you lose your signal. Ours never loses the signal because it predominantly uses GPS via the satellites, but also uses a vehicle speed wire. It does not lose accuracy. It also uses the gyroscope, which gives the system a three dimensional image of the terrain."

The TravelPilot DX-V can be fi tted straight into Ford BA and Territory models with minimal  customisation.

TomTom – One Price: $799 See: www.tomtom.com

This small, portable, lightweight (260 grams) device comes with the same basic fundamentals of other more substantial TomTom models. It uses the smart technology provided across the TomTom range and includes a pre-installed 128 MB storage card. This memory card can be upgraded by simply copying the memory off the original and pasting onto another larger card. The unit does not compromise on-screen size as it comes with a 3.5 inch, 320 x 240, LCD touchscreen. TomTom allows a choice of 47 voices, including Ken the Aussie (Oi, Oi, Oi, I said turn left here…) to guide you on your trip.

The Sensis maps are upgradeable – for example you can also download all the speed traps and red light cameras located in a particular area. New map information can be downloaded into memory from www.tomtom.com. Simply follow the prompts.

TomTom's Remo Behdasht says "As the most affordable integrated product we have ever brought to market, TomTom One makes personal navigation a reality for all, broadening our appeal and customer base".

TomTom's Christopher Behan added that "A map upgrade will be released around June 2006 and this will include the M7 Western Sydney Orbital in NSW as well as other new roads and updated POI (Points of Interest) files. You can upgrade your current map to include routes of all toll ways and how best to avoid them as well as adding your own Poi's (Points of interest) to the already included museums, petrol stations, restaurants etc".

Mio Digiwalker 136 Price: $699 See www.mio-tech.com.au

The Mio Digiwalker 136 is a clever little handheld PDA with an inbuilt high sensitivity antennae, claimed to provide accurate GPS and an MP3 player, which switches off when driving directions (voice and map) are being provided.

It can also warn drivers of more than 600 fixed speed- and red-light camera locations, and can act as a speed warning.

The unit works straight out of the box. Simply turn it on, punch in your desired destination and drive away. When you get there your PDA functions are again at your fingertips (the unit is based on Pocket PC software).

The Digiwalker 136 uses preloaded Sensis map data on a memory card. Your trip progress is displayed on the screen as a highlighted blue line.

You can also see your driving distance, maximum speed, total driving time, total stopped time and the total time.

Navman – iCN 635 Price: $1300 See www.navman.com

This all-in-one car navigation solution is designed for portability between vehicles and matches street-mapping software with the latest GPS katechnology.

Standard features include simultaneous voice and visual driving instructions, automatic and manual zoom for map detail control, ‘Back-on-Track' re-routing when off-course, and an extensive points-of-interest library. It also has an adjustable speed alert function.

The iCN 635 has a high-resolution 3.8" LCD to show its three-dimensional maps. Icons on the map clearly indicate the direction to be taken whilst incorporating distance to the manoeuvre in real time.

The temperature-resistant magnesium case hides a high-precision GPS antenna. A removable 128MB Multimedia Card pre-loaded with Australia-wide map data is included. Internal memory for additional maps is also provided to the tune of 128MB.

Standard provisions include remote control, windshield mounting bracket, 12-volt adapter and storage case.

"We have seen, as more and more consumers embrace the technology and come to rely on navigation in their everyday lives," Navman's Charlie Hirlakoglu. "In response to fantastic growth in the in-vehicle navigation market, we have continued to bring more products to market and improve the overall user experience of our guidance systems. Our iCN series is easy to operate, produces lightning-fast results in route calculation and data response time, and is equipped with the brightest screens on the market."

VDO Dayton – MS5400PKRVM Price: $2999 See www.vdodayton.com.au

This system lets a driver see the navigation display in the car's rear-view mirror. It differs from others that require a driver to momentarily look down from the road ahead to see map directions. Just as when checking traffic behind, the driver's peripheral vision is still focused on the road ahead.

The four inch screen is connected via a single cable that is hidden inside the mirror's arm. It runs up through the roof and down to the navigation system's computer so no bolts or screws needed. As a permanently installed system, it also combines the vehicle's speed sensor and gyroscope data with GPS, to bring navigation accuracy down to within a few metres (depending on map coverage and currency).

Siemens VDO's Gary Cahill says "You get what you pay for in car navigation. With this design, which we've had on the market for six months, you don't have to compromise the car's quality. Take for instance, a Jaguar. Many owners wouldn't want to put a dedicated screen into the console of its classy interior. With this system, though, you can place the navigation computer out of view, say underneath the parcel rack and the display is integrated in a familiar factory-fitted device."

The MS-5400 computer has up to 400MB of dedicated memory, which is more than twice the memory of some other satellite navigation systems in the market, and will allow further enhancements to maps, which are on CD-ROM.

VDO Dayton uses Sensis as its map provider. The Whereisbranded map discs cover all 19 of Australia's UBD street directories and cost between $355 and $395.

The MS5400PKRVM system is remote controlled via a remote. Controllable settings include voice instruction, tone and brightness. An adaptor cable allows for a rear-view monitor to be connected to the system which displays when reverse gear is engaged.