Am 02.01.2010 00:19, schrieb Steve Ratcliffe: > [...] > Some observations > > 1. The sea polygon is probably cut up into small enough pieces first, > before the "cuts" to the hole are made. > 2. Because we do things the other way round, we make the cut a slight > wedge shape, as you cannot send polygons that have touching segments > to the polygon splitting code. This is what makes things look bad. > 3. If you split a sea polygon with a line that goes "through" (around) > a hole then you don't need to add a cut. > 4. Its probably easier to do it by hand, but that might just reflect > my lack of knowledge of GIS algorithms in this area... > I think it should not be too hard to create an algorithm that decomposes a polygon with holes into polygons without holes. I googled for "polygon decomposition" and found a paper describing an algorithm to decompose a polygon with holes into convex polygons, but this seems to be more than we need (and too complex computationally). Right now I have some time so I will have a look at it.
Best wishes Christian _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev