[OSM-talk] Lake rendering

[Sven Rautenberg]

Gustav Foseid schrieb:
> Could someone take a look at lake Østensjøvannet near Oslo, and tell me how
> to fix the mulitpolygons, so both Osmarender, Mapnik and the Cycle Map
> understand them?
> 
> http://www.openstreetmap.org/?lat=59.8815&lon=10.8767&zoom=14&layers=0B00FTF
> http://www.openstreetmap.org/?lat=59.8816&lon=10.8768&zoom=14&layers=B000FTF
> http://www.openstreetmap.org/?lat=59.8816&lon=10.8768&zoom=14&layers=B000FTF
> 
> I have made a couple of attempts, but without much luck.

I think you cannot complete this task until Mapnik gets some software fixes.

One general rule for tagging "holes" within an area is to use a
multipolygon relation and to put all tags on the outer border way marked
as "outer" in the relation, leaving the "inner" way untagged.

This works great in all renderers. Example: Lake with island, or wood
with a clearance.

What if the "inner" way marks something other than "nothing"? Simply tag
it as such. This works great, too. Example: Lake with wood island.

What if this "inner" way has holes by itself? Example: Wood with lake
inside, which has an island with wood.

You can tag the wood as "outer", tagging the way of the lake as "inner",
which renders fine. The lake too is a "outer", with the island as an
"inner" way.

Only Osmarender can render this correctly so far. Mapnik fails (and
Cyclemap's Mapnik fails different than the general Mapnik).

I'd suggest tagging your lake correctly and try to get Mapnik fixed,
instead of trying to find a workaround tagging that works in Mapnik and
Osmarender.

Viele Grüße
Sven