[OSM-dev] MAPNIK - proposal to drop rendering of underground railway lines

Andy Allan gravitystorm at gmail.com
Wed May 16 19:14:43 BST 2007

On 5/16/07, Nick Black <nickblack1 at gmail.com> wrote:
> But what functionality does it add to the map?

"How do I get from pub A to pub B on friday night when I go to London?
Should I just walk? Oh, look, there's a tube station near both"

a) "and I can see there's a line running straight between them, cool,
no need to walk"
b) click... click... (find a tube map) - "Which 'Edgware Road' one is
this one again?" flick back to osm... flick forward again "yeah, I
think there's a direct route. Boy I wish they'd just show it on OSM,
that would be useful"


> Maybe for the trench cut, cut and cover tunnels, but you cant possibly map
> deep tunnels accurately from optical aerial or satellite imagery.

I can't map any tunnel accurately. But I would still add them on the
WCML (or any other railway) to make sure that everything joins up. A
good approximation will do when accuracy can't be achieved.

> This
> equates to mapping the individual paving slabs on a pavement with a GPS
> unit.

No, it doesn't. There really isn't any point in mapping paving slabs -
train tunnels are important and still worth doing.

>The Jubilee line in London has been mapped from space using
> interferometric SAR, as the houses directly above it have sunk by severl
> milimeters since it was constructed:

So it can be done then? All we need is a Yahoo-style agreement with
these guys, and we'll be laughing all the way to the next mapping


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