[OSM-talk] Islands in rivers

Alex Mauer hawke at hawkesnest.net
Thu Aug 23 00:10:51 BST 2007


After being pointed in the right direction for getting the Yahoo WMS
layer(s?) properly lined up in my area, I've begun doing some work on
rivers around me.  At least one of the rivers is large enough to require
the use of waterway=riverbank to define it.

I've run into a couple of problems though:
First, if I try to break the river down so that it's multiple ways, it
doesn't render properly at all: the renderer makes a straight line
connecting the end of the way to the beginning of the way.  If it
happens in a fairly straight section of river, it pretty much doesn't
show up at all.  If it happens in a curvier area, it renders that line
willy-nilly across all sorts of land and whatever happens to be in the
way (generally flooding a big chunk of land).

Is there any way to get this to work properly by using different tags,
or can the renderer (t at h, haven't yet seen how it looks in mapnik) be
fixed to handle riverbanks like it does for coastline?  I don't think my
current "solution" of using one giant way is tenable; the way is already
up around 1000-1500 points, and I've only mapped approximately a 5 mile
section of the river.

Second, islands don't show up at all; I've tagged them as both
waterway=riverbank and natural=island, ordered them counter-clockwise
(opposite of the river itself) and they simply don't show up. (except
when I had the river as multiple ways, and then they only showed up
where the "bad" line was cutting across them).  Again, is there a way to
get these to render properly by using different tags, or can the
renderer be fixed?

For a look at the "islands" problem, have a look at
http://geo.topf.org/comparison/index.html?mt0=googlemap&mt1=tah&lon=-89.5640659&lat=44.4763597&z=14

Google shows the islands approximately as they should appear. The
southernmost section where an island is partially shown is simply
because I have not yet mapped the southernmost loop of that section of
the river.

-Alex Mauer "hawke"

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