[mkgmap-dev] Commit: r1555: Ignore multipolygons with fewer than 2 resolved elements.

Thu Feb 4 21:25:00 GMT 2010

> On Thu, Feb 04, 2010 at 08:50:49PM +0100, WanMil wrote:
>> I have doubts if that's a good idea.
>> If multipolygons are splitted by splitter it is possible that some
>> polygons are dropped because they are not inside the tile bounds.
>> This makes it possible that the outer ring survives only.
>>
>> The definition of the multipolygon says that the tags from the
>> multipolygon are used for the outer polygons ("Tags describing the
>> multipolygon (e.g. landuse=forest) should go on the relation. The outer
>> way(s) should be left untagged, unless they describe something in their
>> own right."). If these multipolygons are dropped the tag information of
>> the multipolygon is lost.
>>
>> I propose to revert this commit unless there are hard reasons for it.
>
> There is no hard reason for the change.  It was just a workaround for
> splitter problems at tile boundaries.  I reverted it in r1560.
>
> How would you find my other patch, which discards ways that are missing
> some points and have no points in the bounding box?  What about multipolygons
> that contain no resolvable polygons?  Could they be dropped safely?

I did not have time to have a look on the patch and I only read some 
statements from the thread. For mp generation it's a good idea to put 
the full multipolygons to the tiles. This makes coding much easier.

The mp code already discards ways that do not intersect the bounding 
box. Intersect not having no points in the bounding box (!).
In case a multipolygon contains no resolvable polygons mp doesn't do 
anything (but log some warnings).

I hope that lots of things will be solved if the mp code handles the 
tile boundaries. I have started today but it will need some time.

I understand that you want to minimize the number of warnings but I 
would recommend to wait until the mp code is improved in that way.

>
> I am looking forward to the splitter fixes.  In the past few days,
> I have been correcting multipolygon and coastline errors in Finland,
> and I hope to be able to enable --generate-sea=multipolygon soon.

That's alway the best way to get a good map! :-)

>
> 	Marko

WanMil