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

Sun May 2 14:08:53 BST 2010

>
>
> On 17.04.2010 20:00, WanMil wrote:
>>> 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
> Hallo WanMil
> Well I do think the patch is working as supposed. However that is not
> really what I find useful. Now on country boundaries there are sometimes
> 10 boundaries on top of each other - is this what you want to achieve?
> I'ld much rather have only the boundary with the highest admin level -
> and have taken quite a bit of code into the style-file to make sure ONLY
> the boundary with the lowest admin_level is put inside the map. Your
> patch makes my style-file useless.
>
> I don't really understand what this patch is trying to achieve. There is
> a patch by Thilo Hanneman (I'm attaching it for you) that makes it
> possible to directly render relations from the relations file, I think
> that is more useful - or don't I understand something here that you
> intend to achieve???
>
> BTW - I'ld much rather have a patch that disables sea, if there are more
> than 500 highway=residential inside the sea polygone, or something
> similar to detect that nothing is flooding. Just day before yesterdays
> alp extract from Geofabrik had one tile inside flooded, and there is the
> dreaded flooding inside Germany as allways (well this one due to
> geofabrik cutting). Maybe you could write a patch for that problem. I
> get tons of comments on my website about sea flooding, no matter in how
> many places I write that this is not solvable and any comment regarding
> sea flooding will get into the trashbin...
>

Felix,
I tried to understand what the patch does. I compiled a map with the 
default style but the changed code section was never called. So I 
suppose I am missing some style rules that trigger the patch.

Can you send me your style file so that I can try to understand the 
patch and maybe extract the good parts of it so that we might commit it?

WanMil