[OSM-newbies] Coastline Rendering

[Zeke Farwell]

Yeah I know "natural=coastline" shouldn't technically be used for lakes.
However, the renderers currenly only deal well with closed polygons.  I have
had very bad luck getting Osmarender to display "natural=water" or
"natural=riverbank" properly using multiple ways connected end to end and
joined with a multipolygon relation.  In these cases I've just ended up
using entirely closed polygons with one way each.

Since this seems to be what the renders can handle for now, and the Lake
Champlain lakeshore is too large and complex for a single way closed
polygon, I decided to just tag it as "natural=coastline"  until I hear that
the renderers have better multipolygon support.  It seems the same descision
has been made about the Great Lakes.  When better multipolygon support
arrives these large lakes should be changed to "natural=water" (or maybe
there should be a "natural=lakeshore" tag specifically for large lakes with
complex coastlines).

Thanks for the input folks.

Zeke


On Fri, Jul 11, 2008 at 12:58 PM, Eric Ladner <eric.ladner at gmail.com> wrote:

> On Wed, Jul 9, 2008 at 11:53 PM, Zeke Farwell <ezekielf at gmail.com> wrote:
> > Hi there fellow OSMers,
> >
>
> Technically, I think, you shouldn't use coastline for a lake, but
> "natural=water".  Coastline is reserved for.. well.. the coast (or
> typically areas affected by tidal forces which is where the great
> lakes probably get a "costline" designation).  From the Wiki:
> "natural=water is for inland lakes, and should not be used for tagging
> ocean coastline. Equally natural=coastline should not be applied to
> the edges of a lake."
>
> This would force you to link all the outer ways into a single "outer"
> way (clockwise), and all your internal islands into inner ways
> (counterclockwise).
>
> If it were me, I'd string as many of the outer ways together into one
> continuous line (form a closed loop if you can) but the limit for the
> number of nodes has been reported to be around 3000 to 5000 before
> problems start occurring.  I've done ways with close to 2000 nodes
> with no problems.
>
> I've done a lot of stuff with rivers, riverbanks, islands, tidal
> lowlands and such, but never a truly internal "lake", so, you might
> have to fiddle with it a tad.
>
> Even after you get your stuff done, unless you're running Tiles at Home
> yourself, you have to wait till somebody actually renders the tile
> before it shows up in the osmarender layer.  Dirty tiles can take up
> to several days, I've seen, so I just started my own Tiles at Home at the
> house to render on demand .  You can check and see when the tile was
> last rendered if you go to informationfreeway.org, zoom in in to zoom
> level 12, hover over the tile and hit the "i" key.  It'll open a
> window showing you when the tile was last rendered.  The Mapnik layer
> only updates once a week (or so).  You can also put it in the request
> queue to get rendered with the "r" key in informationfreeway.org.  The
> coastline viewer says it's about weekly, but there's red flags on
> stuff I know I updated more than a week ago that still shows up.
>
> If you're editing, don't worry about Mapnik so much.  If you get it to
> look right in osmarender, when Mapnik DOES update, it'll be fine
> (99.99% of the time).
>
> --
> Eric Ladner
>
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