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Satellite Navigation GPS Map Accuracy Reality Check

We Need To Check What We Need Before We Buy, And Even Then We Need To Be Careful...

Road SignSat Nav's or GPS Units promise the Earth, or at least the Country where you bought it. Great you think, I can forget about maps and directions, my little Sat Nav will now take me everywhere. Wrong.

GPS Sat Nav's are little computers that rely on a programme to look at where you are, where you want to go, analyse their map, then work out where to go. As such there are plenty of room for errors. The programmes can have bugs and glitches. The route algorithm can choose strange paths. And then there's the maps....

GPS Maps are produced by two main companies, Navteq and Teleatlas. As you can well imagine the task of creating these maps is enormous, and keeping them accurate is a bit like painting the Fourth Road Bridge, that is never-ending.

Both companies have teams of people in specially equipped vehicles driving around recording roads, turns , POI's, etc, all going into producing their maps. So they're continually updating their own base map, but when you buy a Sat Nav you're just getting a snap-shot in time of the latest maps. Some bits will be very new, but others could be quite old.

So what am I saying here? Any GPS Sat Nav you buy will have mistakes, whether through being out of date or through human error, so its really important that if you can, check the GPS is right for you before you buy?

What do I mean? Well, if you're going to be using the device locally, obviously put your address into the shops demo model. Then your friends and relatives. Try Post-Codes and addresses. If you're going to be using it on holiday remember to bring those destinations too and punch them into the units. Buying the GPS for abroad. whether that be business, pleasure or relocation, get the shop assistant to enter as many addresses as possible. This will really get you to understand the shortcomings of Sat Nav's, and you can adjust your expectations, and planning, accordingly.

Take people who live in flats, or "courts". Often these will not be listed at all, and the Post-Code will not take you right to the door. Post-codes and addresses for business parks and industrial estates can be a bit hit and miss too. Always have a paper-map and directions as back-up, and the phone number of where you want to go so you can ask for help!

Map coverage of the UK, France and Germany is pretty good, but other countries can be poor in comparison, especially in rural areas. Areas that are developing fast, like Ireland and Spain suffer because they're building new roads quicker than the Sat Nav Map companies can update them!

I guess what I'm trying to do is manage your expectations about what Sat Navs can do, and bear in mind the following:

There will be missing addresses and Post-Codes on your GPS.

House numbers will occasionally be missing or on the wrong side of the road.

Roads will be missing / in the wrong place / be closed / be the wrong direction / be too narrow etc.

POI's will be out of date - Petrol stations will be long gone, restaurants closed down.

The list goes on.....

Should any of this put you off buying and using a GPS Sat Nav? No way! They are amazing devices, will save you time, money, and get you home when you're lost, I wouldn't be without mine. Just don't leave your common sense at home and blindly follow that voice without double checking road signs too..

Now you're going to ask me which Sat Nav GPS have the best maps. It's generally agreed that Garmin and Navteq have the best maps out of the box, but TomTom and Teleatlas are catching up fast. Tomtom have also introduced mapshare which allows users to alter mistakes on their maps and download other peoples correction too, which could lead to the best maps ever. Or not, it's a bit early to tell.

I'd be happy with a Garmin, TomTom or Navman, just always remember they're not perfect!

Comments / Questions:

I want to buy a GPS that can be used when driving in New Zealand and California. Which make and model would be best suited to this?

Great question! You'd have to get a unit pre-loaded with one counrty or the other, then get the missing maps on DVD (or download them from Garmin), and put them on SD card. Which Garmin you buy depends on your budget - they're all good now.

within 50 yards of my home in dartmouth my garmin send you up a one way street the wrong way, down a road that was closed to traffic in 1966, up a very narrow one in four hill even if you say you are a truck when there are three better routes handy.   they don't seem to know ferry  times or weight limits.

these products are utterly dreadful and i would be ashamed if i made or sold them.  the GPS is useful, the maps are just hopeless. tim.

Oh dear! Make sure you report it to Garmin!

How can I stop sat nav devices treating our private drive as a public route ? Is there any central organisation I can contact?

Although Private, it may still be a right of way.... but you could tell Navteq and Tele-Atlas they're the two big players. And maybe put up a sign "Road Too Narrow For Vehicles"....

I am the driver of a 40 ton articulated lorry are there any satnavs which have 7.5 ton limit, industrial estates built in or for sale as a add on. Neil.

Check out this website about a low-bridge POI file that you can download for TomTom's and Garmins': http://www.lowbridges.com/
I understand that they're working on a weight-limit POI file too.

I am moving to Spain in June, Granada province of Andalucia - I have read that Tom Tom Europe is the best option - any advice would be appreciated. Judie.

A tomtom europe or a Garmin 250 would be good choices as entry-level devices, just be aware that all maps in rural Spain aren't that detailed. Go armed with some addresses in Spain to a shop that sells them, Halfords is good for this, ask for a Demo, and see which unit comes top in a test of trying your new addresses.

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