The Basics - What is GPS?

GPS or the Global Positioning System is the operation of 24 satellites in orbit around the earth that allows GPS receivers to pinpoint their location by use of mathematical calculations.

The Basics - How does it work?

The GPS system uses Trilateration to calculate you location us8ng a minimum of 3 satellites at any one time, these signals are compared with a database of maps within the unit and your current location is calculated and displayed. The current GPS system is accurate to around 10 meters and is controlled and operated by the American Military. Europe's answer to the American GPS system is Galileo which should be operable in 2010 using 30 new satellites and providing accuracy down to 1 meter. If you want to know more then check out our GPS Explained article.

The Basics - What good is it to me?

Knowing where you are has always been useful and being armed with this information and an old fashioned map is essential for travel. However our roads are becoming more and more congested and complicated in layout and restrictions. GPS systems combine knowing where you are with a route planning capability, they can then take the hassle out of navigating providing you with turn by turn guidance to your destination. The best systems go further by knowing about useful locations like petrol stations and some even know about the traffic conditions.

The Basics - Your needs?

As with all technology it's all too easy to be overcome with a mixture of gadget blindness and technology meltdown when confronted by shelves or pages of GPS Navigation systems. Before you even start to browse the web for the latest SatNav systems take a moment to think why you need a unit and what you'll be using it for. Then use the following section to work through your needs before venturing out onto the web or high street.

Types of System - In Car (fixed)

Perhaps the first experience many have of SatNav is renting a car that has inbuilt SatNav. These systems are often integrated with the cars entertainment systems and have large colour screens, manufacturers are able to keep prices amazingly high with the list price of these options often being in excess of £1500. Unless you like being mugged while buying a car, or the dealer throws it in FOC then avoid these like the plague. They are often difficult to use with poor data entry (very few are touch screen) and the maps go out of date quickly and are rarely updated.

Types of System - Portable

Probably the most popular system type in the UK, these units are dedicated in car GPS systems that are easily transferred between vehicles and are normally held in place with a windscreen sucker mount. Makers such as TomTom, Garmin and Navman have become familiar names and a record 650,000 all in one units were sold in the UK last year. There are now finally units specifically designed for motorbikes which are more robust and use Bluetooth to get the audio inside the crash helmet.

Types of System - PDA Based

Those who reject the In Car systems first chose to use the PDA as the alternative, PDA's have always been a curious gadget with many owners not really knowing why they carry them. So when companies like TomTom and Co-Pilot added a cabled GPS option to the Compaq Ipaq and maps on CF flash cards a whole new sector was born. Today the PDA based system has been somewhat overshadowed by the Portable, however there are still excellent systems available and they often have cutting edge features ahead of the all in one units.

Choosing - Accuracy

Using the Ronseal principle a SatNav system must do what it says on the tin and accuracy is key. The current American GPS system should allow systems to navigate to around 10 meters accuracy, it's vital that your chosen system is as accurate as possible you don't want it thinking you are further down the road than you really are or you'll make a wrong turn.

Choosing - Reliability

Sounds daft but reliability should not be assumed. Check your unit has the latest chipset (SiRF Star III) the latest chipsets are far more accurate and less prone to struggling amongst high buildings in town, or when roads are overhung by trees. Another key area here is to check if your car has a heat reflective or heated windscreen, if it has then a unit with a built in GPS antenna may be trouble as it won't be able to get enough signal strength. The tip here is to always pick a unit that can have an external antenna added, which means you can run it to a position where it can see the satellites (many cars have a gap in these reflective windscreens behind the interior mirror).

Choosing - Speed of Calculation

Two things to test for here, first is the TTF or Time To Fix, you want a unit that quickly acquires enough satellites or "lock" to start navigating, otherwise you'll sit frustrated in car parks waiting for your SatNav unit to wake up! After the initial power up (which can take longer) every subsequent TTF should be under 30 seconds, the latest units manage under 15. All this is pointless if the unit takes an age to calculate your route, again you want something that calculates quickly in order to get you moving. Plus this calculation needs to be speedy when you take a wrong turn (it will happen) you need it to get you back on track quickly before you get further lost.

Choosing - Mapping / Navigation Quality

Almost all systems use either Navteq or Teleatlas maps, in fact many company's will switch between the two providers frequently as their software is written so that it is abstract from the mapping data. You can't really be expected to choose between systems based on mapping quality as it changes so frequently. What is worth checking is the upgrade policy of the system you choose and the likely cost to buy the updated maps. After all a SatNav system with out of date maps is like ant virus with no updates. Also ensure you check the coverage of the systems maps cover the area you intend to drive in, not all systems cover Ireland on the standard UK maps and should you buy a European map check it is street level and not just major roads and cities or you may find it next to useless. Don't be suckered into buying a system with full European maps if you never drive abroad (or rarely) you could be paying a £150 premium! instead check that individual country maps are available as an after sales purchase.

Navigation quality on the other hand varies hugely between systems. Some systems offer a host of controls to let you choose if you want more motorways or A roads, if you prefer a more direct route, or ones avoiding things like the congestion charge zone. However in our experience these are best left well alone unless you fancy driving through a farm on single track lanes! What does count is the type of routes chosen, you really want the unit to choose the quickest route which not always the most direct. A good test is to deliberately take a wrong turn and see what happens, poor units will just tell you to make a U turn, a good unit will calmly get you back on track.

Choosing - Interface and Audio

The interface on a GPS navigation system is critical perhaps more so than on any other form of consumer electronics as it will be used while you are in control of a vehicle at up to 70mph. Therefore you are looking for something simple, clean and effective, if it looks like a game of space invaders or that only a geek could operate it steer well clear. You are looking for something that is symbol based with a clear easy to understand real time map, you need to be able to look at the screen and quickly see where you are and what the next instruction is. Useful data like distance to next turn, current road name and next road name are good but only if they are easy to read.

You should of course be looking at the road and not reading the screen, try to think of the screen as a backup to the spoken instructions. The audio must be very loud, if you are in a store make sure it's embarrassingly loud, you'll want it to be heard over the road noise and your radio. Spoken directions should be clear and use UK terminology like motorway (not freeway) some systems even speak the actual road name which can be very useful.

Choosing - Power

The last major category of note is power. Sounds basic but you need to check that the power lead will work in your vehicle and that it will reach, some system have an amazingly short power lead. Then there are the battery powered units, these may be useful if you swap the unit between cars for short journeys and can't be bothered to de rig the power lead each time. You should expect a battery that will run for at least 4 hours.

Extras

We like many other review sites will always talk about the extras, after all they are shinny and often the only difference between 2 systems. However don't even consider a system if it hasn't matched you basic needs, only then look at the extras.

These include useful extras like traffic information, it is the holy grail of SatNav to have a system whereby the route is adjusted to avoid traffic. Many systems claim this but to date only 1 (SmartNav) actually does it and this is purely down to the quality of the traffic info. Watch out for systems that take free TMC data and then charge you to get it via Bluetooth data connections and your mobile phone, they are both expensive and provide out of date info.

POI or Point of Interest are excellent and every system should have them, this is the ability to have groups of locations like petrol stations and cash points visible on the map and also the ability to navigate to them. Ideally you are looking for a system that allows you to import any set of POI's and not just their own ones which some even have the cheek to charge for. Possibly the best POI data is the UK speed camera map which although no longer free is still very cheap over at pocketgps.co.uk.

Other extras include, translation software, MP3 players and even hands free Bluetooth phone systems, these are generally very poor in comparison with buying a car kit or an MP3 player design to do the job and should not sway your choice of system.

Overall

Use this GPS Navigation Buyers guide as a checklist, take your time and read as many reviews as you can including those in our own SatNav Reviews section.

Published - 04/06/2006

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