[OSM-talk] Mapnik handling of highways that are also landuse...

[Steve Chilton]

Dermot

There are two reasons why your "tag combination ought to be able to
render correctly as is" statement is not valid.
Firstly - as Thomas pointed out - mapnik likes one feature per way.
Secondly - landuse=grass is not rendered at the moment (because of the
vast disagreement on the whole landuse/natural/grass thing).
What I am guessing you have on the ground is a residential square with a
road round the outside and a grassy bit in the middle. There is no way I
know of for mapnik to interpret this correctly from a double-tagged
single way like this. It would have to be able to draw a line, a road
fill, a second line, and then the grass fill.
Where these occur in areas I have seen (many grass filled squares in C
London) two parallel ways have been used - and yes I know that people
are using leisure=park "incorrectly" in order to get them rendered, but
probably excusable in London as they are often formal park/recreation
areas.

Cheers
STEVE

Steve Chilton, Learning Support Fellow
Manager of e-Learning Academic Development
Centre for Learning and Quality Enhancement
Middlesex University
phone/fax: 020 8411 5355
email: steve8 at mdx.ac.uk
http://www.mdx.ac.uk/schools/hssc/staff/profiles/technical/chiltons.asp

Chair of the Society of Cartographers: http://www.soc.org.uk/

SoC conference 2008:
http://www.abdn.ac.uk/cartographers08/

-----Original Message-----
From: talk-bounces at openstreetmap.org
[mailto:talk-bounces at openstreetmap.org] On Behalf Of Dermot McNally
Sent: 28 August 2008 00:49
To: osm
Subject: [OSM-talk] Mapnik handling of highways that are also landuse...

Folks - with reference to this:

http://www.openstreetmap.org/?lat=53.72339&lon=-6.34273&zoom=17&layers=B
00FTF

...which is a section of the Mapnik render of the outcome of the very
successful Drogheda Mapping Party in Ireland. Towards the centre of
the map, you'll see what is represented as an oval area of residential
highway. I can almost see why, but it struck me that it represents
unwanted behaviour that could possibly be fixed.

What we have here is a closed way of type highway=residential.
Importantly, it isn't tagged as an area. It _is_ tagged (the same way)
as landuse=grass. So without understanding the internals of Mapnik,
it's as though the landuse, which applies at area-level, infects the
highway tag and causes it to be considered as an area too.

Clearly, I could simply draw a second way through the same nodes, and
there are plenty of heated discussions over which approach is the
saner. But it feels as though this tag combination ought to be able to
render correctly as is.

Dermot

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