yes, I added a few system.out.println and found that a lot of sea or land polygons are
completely dropped by the filters, for example a polygon with 14 points
was reduced two 3 points by the RoundCoordsFilter and then thrown away
by another.


> The mp algorithm tries to do as few cuts as possible. So it cuts at that
> horizontal or vertical line where it can cut the most inner polygons. It
> does not check if the cutting line is longer or not (because it doesn't
> know and it's hard to estimate without implementing your own cut algorithm).
>
> As a first quick hack it would be possible to add a check if an area is
> too thin and to revert this cut. That leads to the question: Is there a
> definition for "too thin"?

In the tile splitter I decided that a ratio of 1:4 or less is nice, but I have
no theory for that.

> > yes, I agree. So I'll try to find a better mp algorithm.
>
> All you have to do is to improve the
> private List<Way> cutOutInnerPolygons(Way outerPolygon, List<Way>
> innerPolygons)
> method in class MultipolygonRelation. Good luck!
>

OK, thanks. Let's see...

Gerd