[josm-dev] Clockwise coastline, anti-clockwise water

[D Tucny]

2008/7/6 Dirk Stöcker <openstreetmap at dstoecker.de>:

> Hello,
>
> I try to verify patch http://josm.openstreetmap.de/ticket/737
>
> Now beside the fact, that this contains an better algorithm for clockwise
> coastline detection, it also fixes a set of problems in the old code.
>
> Now the result is, that the code works as expected and reports "clockwise
> coastline" and "clockwise land" as error. But it also reports
> "anti-clockwise
> water" as error. There is no doubt, that the original code wanted to do
> that also, but I found not indication on the website why?
>
> So my questions. Should water be drawn clockwise or anti-clockwise, or can
> the check be removed?
>

Coastline should be clockwise, around the water, typically you wouldn't have
an entire sea of ocean closed area loaded into JOSM though, but, you could
well have islands in even a small area... Islands are represented by a hole
in the water, or an anticlockwise closed area... The check reporting an
error is due to the fact that if an island was drawn with a clockwise
coastline, it would be representing the water... Also, a lake/pond, should
be water rather than coastline so it would flag this too...

Land should be a/some clockwise way/ways around land and water should be
a/some clockwise way/ways around water... So, it should be an error if the
way is anticlockwise...