[Tagging] Mismatched Level of Detail in highways vs. other elements

[Martin Atkins]

On 04/07/2013 12:13 PM, Clay Smalley wrote:
> I do some mapping in SF too. The Muni Metro lines weirded me out when I
> first saw it, and I looked up the proper practice on the wiki as well as
> looking for a few examples in Europe, and it seems that the best
> practice is to just add railway tags and the proper relations to the
> street whenever it runs along a street, and as a way by itself when it
> runs in its own right-of-way (such as the J line's jog around a hill a
> little south of Dolores Park).
>
> I'd support mapping the Muni Metro lines the European/more common way,
> if nobody else has any objections.
>

I was actually leaning towards that too... that is, tagging the street 
as also being a railway, and representing the double-tracked off-road 
segments as a single way each. It's more consistent with how the highway 
network is tagged right now, and there are a lot more highways than 
there are railways in San Francisco.

However, I'm hesitant to destroy the detailed work done by other 
mappers, both because that's disrespectful to the time they invested and 
because those details interact with other objects in the map that would 
also have to have their detail reduced. For example, a mapper has 
represented the fact that there is a physical wall between the two 
tracks as they enter the subway tunnel just to the east of the 
intersection I showed.

At the same time, we lack the tagging required to do a detailed modeling 
of the physical street layout today, and even if we had such a tagging 
scheme I'm not sure that many mappers would have the time or energy to 
implement it.