[OSM-talk] Subway station vs. subway entrance

[Frederik Ramm]

Hi,

>> When mapping the subway network of a major city... should we tag just one
>> node per subway station, or should we tag every subway entrance[1]??

> I would prefer to have only one icon per station, placed in the middle.
> This should be sufficient, because when you are near this point one can 
> usually see the entrances.

No. We will someday want to use our data for pedestrian routing - 
automatic generation of instructions like "cross road at intersection 
blah and then enter tube station foo". This is impossible without the 
entrances mapped.

(It is actually the same with large(r) railway stations - it is not 
always obvious from which side of the tracks there is access!)

This calls for the not-yet-implemented "varying level of detail 
dependent on zoom level" feature. Ideally, you want to map the whole 
subterranean area of the subway station with all entrances, plus the 
actual tracks, plus a hypothetical "centre point" that is drawn on the 
low-detail maps where entrances just clutter up things.

I think that for the time being, mapping the centre point (as 
railway=halt name=...) and the entries (perhaps inventing a 
"railway=entrance" coupled with the exact same name used for the 
station?) would be a good compromise. Adding the footways would be a 
plus but there's rendering issues - if you tag them as "tunnels" you 
will get very undesirable results. Most subway stations are really large 
underground "places", and we have the same issue with surface places 
where a number of ways or roads meet in an area where you can move 
around freely - it's not properly mappable currently.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00.09' E008°23.33'