[OSM-talk] [Talk-GB] NCN refs - consistency

[David Earl]

On 11/07/2007 09:22, Richard Fairhurst wrote:
> David Earl wrote:
> 
>> Sustrans, who developed the network, uses 'NCN' as the abbreviation.
> 
> Actually, sometimes they use NCR and RCR!
> 
> http://www.sustrans.org.uk/webfiles/general/South_East_Annual_Report_05_06_print_version%5B1%5D.pdf
> 
> I think it's been observed on the talk@ list that ncn_ref is quite an  
> insular tag, and cycle_ref would be better. Adding lcn_ref, too, would  
> seem to exacerbate the problem.
> 
> But for the time being I just use NR47 and RR47. (Am not very good at  
> remembering to add route=cycle, though... slapped wrists.)
> 
> The free text "proposed NR41" that Andy cited is also one of mine.  
> This is for a route which will be NR41 but isn't, yet. Any thoughts on  
> a better way to tag this?

I though you were asking about the tag value, not the tag name.

There's a problem with the same way being used by multiple routes in 
general, and how to link up with their identifiers. The route tag 
doesn't really work - has been commented on several times on this list. 
I wonder if we should try to clear that up rather than just address NCN.

Considertations: what if two NCN's share the same way (this occurs in 
Cambridge). General point: what if two or more bus routes share the same 
way, or three bus routes, two ncns and two highway designations all 
belong to the same way. What general mechanism could support this?

How about the following (don't worry about the actual tag names for now, 
it's the principle I am thinking about):
   route=id1;id2;id3
(where id1 etc are *any* strings of the mappers choice) and then
   ref:id1=11
   route:id1=ncn
In this way we can know that there are three routes belonging to this 
way; that the first is a national cycle route and its reference is 11. 
Whether ref:id1=11 or ref:id1=NCN11 or whatever isn't too important: 
consumers can choose to extract only the number from the ref if they want.

And this is general. Consider my last example:
   route=a;b;c;d;e;f;g
   route:a=ncn
   ref:a=11
   route:b=ncn
   ref:b=51
   route:c=bus
   ref:c=101 # i.e. route of bus number 101
   ...

I'd be inclined to use more meaningful identifiers than a,b etc, but the 
point is they are only used to tie the multiple routes to their 
individual properties. e.g.
   route=ncn11;ncn51;bus101;bus37
   ref:ncn11=11
   route:ncn11=ncn
etc

David