[OSM-talk] Observed vs. official designation [was: Oxford High Street classification (Was: Bus sluice/gate)]

[Gervase Markham]

David Earl wrote:
> I disagree.
> 
> (1) It is singularly unhelpful for a user of a map to find that the 
> situation on the ground is different from what the map says. 

I completely agree. But people don't "use" the raw OSM data. They use 
renderings of it, and routing algorithms which interpret it.

Therefore, the raw OSM data should contain information sufficient to 
produce an "official" map showing official road designations, and a 
"consumer" map showing the actual current physical state of the road. 
Such a consumer map might also show e.g. short term roadworks, and so on.

If the highway tag reflects the official position, and ancillary tags 
modify the "defaults", you can do either. If it reflects the current 
state of the road, you can only do the latter.

> (2) It is very hard to get the "official" information. Most of us only 
> have what we see in front of us to work from. It is impractical.

Official information is on every road sign. If my road is the B1250, 
then it's a B-road, and should be graded secondary. But I then might add 
speed limit, width restriction or other tags to indicate navigational 
complexities.

> (3) The vast amount of data already there is tagged by observation. 

It seems to me that there is varying practice in this area.

> While no doubt we could change a certain amount automatically, there 
> would always be loose ends - especially for the cases affected by the 
> reason the change was being made. And even having changed, some people 
> will continue to tag things the way they want rather than following a 
> consensus (though that already applies the other way round too).

Indeed.

> Having said that, I see no problem in having some additional information 
> which gives the "official" designation if different. For example - 
> "ref:official=A120" or "highway:official=primary".

This reduces the problem, but still means that the primary designator is 
a subjective measure of road quality (and could therefore be assessed 
different ways by two different mappers) rather than an objective 
classification.

Gerv