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Could someone check a UK postcode for me?

 
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finisterre
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Joined: Sep 02, 2006
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PostPosted: Mon Oct 15, 2007 1:55 am    Post subject: Could someone check a UK postcode for me? Reply with quote

N1 1LX is located in Liverpool Road, Islington, London.

When I look it up on TomTom it gives me Lonsdale Place, Islington, London.

Anyone else get this? If so, any idea why?

Thanks,

Fred.
(PocketPC with V6.010 (7720) and Western_and_Central_Europe v675.1409)
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mostdom
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PostPosted: Mon Oct 15, 2007 2:35 am    Post subject: Reply with quote

Just tried both on Google maps and the are so close together, they could well be the same location. I also tried it on the teleatlas report site and it shows the postcode it the right place.

It could be a fluke, but if it is a concern you could report the error to teleatlas on thier website.
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finisterre
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PostPosted: Mon Oct 15, 2007 4:40 am    Post subject: Reply with quote

Thanks Dom, but I did a reverse look-up on the post code and ALL addresses in it are LIVERPOOL ROAD addresses.

Can anyone try a look-up in TomTom.

Thx.
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Oldboy
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PostPosted: Mon Oct 15, 2007 6:48 am    Post subject: Re: Could someone check a UK postcode for me? Reply with quote

finisterre wrote:
When I look it up on TomTom it gives me Lonsdale Place, Islington, London.

Anyone else get this? If so, any idea why?
Most, if not all, TTs will give the same result.

The problem is:

1. Because the TT is a device that Locks to the road, the road doesn't have to be drawn with High Precision. Try going down a Slip Road when the Route takes you straight on and it will be some time before the TT notices.

2. The Postcode location is defined as a lat/long co-ordinate. If you look up a Postcode on AutoRoute, Google or StreetMap, it is never shown exactly against the road (although sometimes more accurate than a TT).

So bearing in mind the 2 factors above, the TT searches for the nearest road to that co-ordinate, and snaps to it. In this instance there is only about a 20yard gap between the 2 roads. The graphic only has to be a couple of yards out and it chooses the wrong road.

My own method is if I get the wrong road for a Postcode Input, is to use Browse Map to find the location and then adjust the cursor and use Navigate to ... on the Browse Map Menu.

There are several ways of Route Selection and the Point on Map is probably the most accurate.
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TT 910 V7.903: Europe Map v1045
TT Via 135 App 12.075: Europe Map v1120
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finisterre
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PostPosted: Mon Oct 15, 2007 7:14 am    Post subject: Reply with quote

Thanks Oldboy. It's at least nice to know why it happens.

I wonder if they'll ever be able to come up with a better and more foolproof solution.
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Oldboy
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PostPosted: Mon Oct 15, 2007 9:00 am    Post subject: Reply with quote

I think while Snap-to-Road is used, there will always be a problem.

However I think I would prefer not to see my position wandering off the road graphic while I'm driving along a road. Wink
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Richard

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Calomax
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PostPosted: Mon Oct 15, 2007 9:12 am    Post subject: Reply with quote

Different but similar problem. A couple of weeks ago I set TT to navigate me to Eastleigh, using city centre as the address. It actually took me to the centre of Chandlers Ford which is about 4 miles away.

But I have now tried using advance planning to find a route from the centre of Chandlers Ford to the centre of Eastleigh and it worked fine.
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Oldboy
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PostPosted: Mon Oct 15, 2007 9:18 am    Post subject: Reply with quote

City Centre (or Town/Village) behaves in a weird fashion sometimes. It seems to depict an area, rather than a location.

If you use Travel via, it will often just skirt round the Ring Road/Bypass and not even enter the City/Town/Village.
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TT Via 135 App 12.075: Europe Map v1120
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barryd
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Joined: Mar 27, 2004
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Location: Cheshire, England

PostPosted: Mon Oct 15, 2007 11:49 am    Post subject: Reply with quote

In TomTom Navigator 5.21 on my Pocket PC this postcode works fine. It shows as Liverpool Road in the list and displays on the map as Liverpool Road 201-279/130-164. So presumably a postcode data issue between versions.
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trafcam
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PostPosted: Mon Oct 15, 2007 3:25 pm    Post subject: Reply with quote

Just had a quick look at the Postcode Address File (PAF) data from the Royal Mail for that postcode, and it seems to show as 53130 East, 18400 North. If you put that into www.streetmap.co.uk (you have to enter the postcode, then edit the obvious numbers in the address bar, including adding a zero on the end of each as they appear to use metre-precision) it does in fact point to Lonsdale Square. The numbers they (streetmap) have for N1 1LX are different, though, so I don't know where they come from. It implies that TomTom uses the PAF data, though.

I don't have that level of detail from later versions of the file (the one I quoted is probably a couple of years old) so I can't say whether it's changed. The grid easting and grid northing for a given postcode are the distance east and north, in tens of metres (hence the adding a zero earlier) to the mean centre of the postcode from a point a little south west of the Scilly Isles. Given the odd shape of some postcode areas I guess it's likely that some data might cause this issue, also there is no way to know the size of a postcode area from the data, only it's centre point.
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Oldboy
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PostPosted: Mon Oct 15, 2007 6:06 pm    Post subject: Reply with quote

trafcam wrote:
.... only it's centre point.
And that's not always the case. Wink
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