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[mkgmap-dev] Multipolygons and disappearing coastlines

From Steve Ratcliffe steve at parabola.me.uk on Mon Dec 28 15:35:41 GMT 2009

On 28/12/09 11:46, WanMil wrote:


>> Aside from that, the multipolygon code already does duplicate the way
>> before removing the tags from the original. Duplicating it again can't
>> be the right solution.
> Only the outer way is duplicated. Inner ways seems to be kept but all
> tags are removed.

Only tags from the inner way that are also present on the outer way
are removed according to the code.

But yes, maybe they should be duplicated as well, I'm not against
duplicating the ways (and I like Mark's second patch), just against
doing it twice without a rationale.

This history as far as I can remember for removing tags from the ways
in the manner that it is done is to prevent duplicate polygons in cases
when people have needlessly/incorrectly/historically tagged both
the relation and the ways that make it up, particularly in the
lake-on-an-island-in-a-forest case.

I've read the links that you posted earlier in the thread and I'd
would like to see the code updated to follow the given algorithm
now that there are a lot more relations being used.


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