TT730 - Odd Speed Limits

ootoph · Occasional Visitor Joined: Jun 05, 2004 Posts: 20

Using the map correction feature, I marked a long local stretch of road as having a 40mph limit, the input being accepted by the machine. When driving down the road, TT showed the limit as 39mph. This is repeated despite attempts to correct the limit.

Certain sections of the M25 around the Reigate area also shown to have odd speed limits.

Is it me?

GPS_fan · Posted: Thu Aug 07, 2008 9:08 pm Post subject:

This has been well documented elsewhere, but it seems to be caused by a rounding up error in the conversion from km/h to mph.

It's hoped that a software update will rectify this, but we're at the mercy of TomTom.

The curious speed limits around the M25 have probably been caused by somebody submitting a MapShare correction for roadworks or something whilst MapShare should only be used for permanent changes
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mikealder · Posted: Thu Aug 07, 2008 9:09 pm Post subject:

It is not your fault, this is a known bug within the software that seems to affect the UK more than the USA (even though both countries use MPH) - it is something to do with rounding errors IIRC

I have given up using this feature until they fix it, all you are doing in using it at the moment is degrading your map data through no fault of your own - Mike

Andy_P · Posted: Thu Aug 07, 2008 9:10 pm Post subject:

No it's not you. It's a bug/limitation of the Mapshare system.
The limits seem to be stored in km/h and then converted on the fly if you are using MPH.
The numbers get rounded up and down to give these wrong results.
It's been discussed on this forum a few times, and TomTom have been made aware of it, but whether anything gets done, who knows?
Meanwhile, more and more parts of the map are being corrupted by wrong speeds!

Andy_P · Posted: Thu Aug 07, 2008 9:19 pm Post subject:

Wow, three replies (all broadly in agreement)in two minutes!

Don't forget you can decide exactly which type of corrections you want to use and ignore the rest.

Set it up in Change preferences/Map corrections / Correction preferences.

dhn · Posted: Fri Aug 08, 2008 12:04 am Post subject:

mikealder · Posted: Fri Aug 08, 2008 7:16 am Post subject:

If you are a member of these US based forums can you tell them not to complain on a forum, please complain to TomTom - if enough of us using imperial measurements on the device complain they might do something to fix the issue - Mike

dhn · Posted: Fri Aug 08, 2008 12:06 pm Post subject:

Andy_P · Posted: Fri Aug 08, 2008 12:58 pm Post subject:

Has anyone got a decent reply from TomTom about THIS issue yet?

GPS_fan · Posted: Fri Aug 08, 2008 1:05 pm Post subject:

It should be simple enough to rectify because it only needs rounding up to the nearest 10 (or maybe 5 to allow for 5mph increments).

This is the kind of fundamental flaw which should really be ironed out in alpha or beta testing.
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ootoph · Occasional Visitor Joined: Jun 05, 2004 Posts: 20

trapper · Posted: Tue Aug 19, 2008 3:50 pm Post subject:

Well, I wish it was only a mile or two per hour error, on my trips recently from Jnct 22 on the M25 to the M11 my new TT730T reckons the speed limit is 49MPH Exclamation

As soon as I get on the M11 its back to 70mph Smile

This problem only after TT Home decided to 'update' my 730 with incorrect data Crying or Very sad

GPS_fan · Posted: Tue Aug 19, 2008 4:04 pm Post subject:

trapper · Posted: Tue Aug 19, 2008 4:16 pm Post subject:

Just sent this to TT:

(After TT Home 'Updated' my new TT730T the M25 jnct 22~27 shows as having a 49mph speed limit whereas before the 'update' it was 70mph.
Would you please advise me how to correct the error caused by your download? I am concerned that the unit may now show a 60mph speed limt where in fact it is a 50mph speed limit and so speed camera risks are very obvious! I could happily be travelling at 57mph and get a summons for speeding!!)
END.

I will see what they have to say, isn't it rather risky letting members of the public change speed limits Question

I can see if road works caused a 'temporary' reduction, however the TRUE speed limit is that set by the powers that be and that is the one that should be shown. After all the Motorway network is 70mph unless signs are shown showing a reduction for all to see, so if you are doing 69 after passing the warning 50mph signs you deserve to be caught!

The biggest area's of concern are the A roads, with 40/50/60 limits governed by street lamp spacing and local factors, these are the ones someone unfamiliar with the area could get caught out if the speed limit is 50 and some 'kind soul' changed this to 60.

GPS_fan · Posted: Tue Aug 19, 2008 4:34 pm Post subject:

The biggest problems here seem to be:

1) MapShare is supposed to be for permanent changes

2) the mechanism for changing speed limits is somewhat fiddly and incorrect speed limits may be submitted accidentally

Then, of course, there's also the question of corrections being submitted maliciously to avoid people being routed along certain roads.

You do, however, have the option in MapShare Preferences to select only the corrections which you have made yourself and these errors will not be used by your device.
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