[OSM-talk] address interpolation

[David Earl]

On 30/09/2009 09:51, James Livingston wrote:
> On 28/09/2009, at 2:22 PM, Marcus Wolschon wrote:
>> 25A-25C should work with addr:interpolation=alphabetic .
>> However not all software that supports interpolation at all,
>> supports this interpolation-mode yet.
>>
>> 25-25A would not.
> 
> I'm not sure you how you can interpolate things like this correctly if  
> you're just using a single interpolation way. For example I've seen  
> both 23-25-25a-27 and 23-25a-25-27, with the 'a' house being whichever  
> one was built second or isn't the primary residence.
> 
> Whenever I've encountered something like this, I've just broken the  
> way up, so that there is one for ...-23, two plain nodes to 25 and  
> 25a, and another way for 27-.

I wasn't suggesting that 23 would be included in the interpolation, 
merely that the first item of an alphabetic interpolation could be "no 
letter". Presumably you could start at B or D, so why not no letter at 
all, it's not ambiguous.

And I think the previous point about other alphabets is a red herring 
too: basically "no letter" can precede all other letters in whatever 
alphabet. If there's ambiguity in the alphabet due to the glyph 
appearing in more than one, then that's a problem anyway, and would, 
perhaps need a tag to sequence. (Of course if the way of sequencing 
houses in another alphabet doesn't follow lexical ordering then all bets 
are off anyway).

It's not a big deal this, it just seems to fit the circumstances more 
naturally. In the case I was dealing with it would have meant I could have
   25->25D  27->27C  29->29C
instead of
   25  25A->25D  27 27A->27C  29  29A->29C
the first non-lettered item belongs naturally in that sequence 
(especially as on the ground, the each of the 25's, 27's and 29's were 
physically joined as terraces), and certainly in the UK there's 
generally no "A" without a corresponding no-letter in the sequence. 
OTOH, letters > A are pretty unusual, and I am surprised they didn't 
renumber the street in this instance, as everything nearby had been 
rebuilt as well and they'd even move a street name from one street to 
another.

David