[Talk-GB] Ground truth v legal truth

David Woolley forums at david-woolley.me.uk
Fri Jul 19 11:55:31 UTC 2019

On 19/07/2019 12:36, Philip Barnes wrote:
> I cannot dispute this is legally a primary, OS Opendata shows it.

I would say the logical consequence of that argument is that no road 
should be mapped as tertiary, as, unless taken from OS, it is a 
subjective judgement and can't be consistently verified.

I think mapping it in conflict with a published official designation 
will devalue OSM.

As you hint, the correct thing to do, in mapping, is to map verifiable 
attributes that would make a rational router want to avoid it. Beyond 
that, like any tagging for the renderer issue, it is up to routers to 
use more than the primary classification in deciding whether to route.

This is going to get more important, with the continuing trend is to 
reduce signage, on the basis that it distracts drivers, and they have 
access to GPS maps so don't need it.

(As a variation on the last point, one of my pet hates, these days, is 
how few houses now have house numbers in the UK.  It make it difficult 
to give accurate locations for fly tips - many of the apps use sources 
like Bing, which use address interpolation, and can be a long way out in 
some cases.  I believe some US cities have bye-laws requiring them to be 

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