[mkgmap-dev] [PATCH v1] Handling of boundary multipolygons

Sat Apr 17 19:00:16 BST 2010

> I am thinking about how to handle boundary multipolygons and want get
> some feedback and ideas from you.
>
> There are two possible ways to use boundary information:
> 1. Draw the boundaries as lines
> 2. Draw the boundaries as polygons with different colours for different
> administrative levels
>
> I think the 2nd option cannot be realized (at the moment). I see no way
> how to define a style that differently colours adjoining polygons with
> rather identical tags (e.g. boundary=adminstrative, admin_level=2).
>
> So let's concentrate on the 1st option.
> One way may be part of different boundary relations. (admin_level=2&&
> admin_level=3&&  admin_level=4 ....). To be able to process all of them
> with the style system the way must be duplicated for each relation.
>
> The multipolygon handling of boundaries might work as follows:
> For all ways (role=outer and inner) part of the boundary relation
> - Clone the original way
> - Tag the cloned way with the boundary information of the mp
> - Remove all tags from the original way that are also contained in the
> mp (with the same value)
> - Split all closed ways (polygons) in two ways to ensure that only ways
> are tagged with the boundary information
>
>
> What do you think? If no one really complains I will start implementing
> this (and expect that it will be accepted when I am ready :-).
> In case other multipolygon type also require such a processing we might
> add a config file in future which types are handled in this way. So this
> is ready to be more generic.
>
> WanMil
>

Why talking so long? Implementation was quite easy so please try this 
patch and post what you think about this patch.

I will post v2 with some more comments in the source code if it should 
be committed.

WanMil
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