[mkgmap-dev] type=multipolygon relations

Sun Jan 19 18:47:15 GMT 2014

Hi WanMil,

I think your example is not valid. One rule in that wiki says:
"If an endpoint is shared by more than two unclosed ways, it's ill formed
and a closed polygon can't be reconstructed unambiguously."
I think both end points of 3 are shared by three unclosed ways.

Gerd

WanMil wrote
> Hi Gerd,
> 
> from my point of view it's ok to remove duplicate ways from mps.
> 
> Anyhow I didn't find a sentence on 
> http://wiki.openstreetmap.org/wiki/Multipolygon that this is disallowed.
> I can think of two touching inner polygons:
> 
> 11111111111111111111111111
> 1                        1
> 1      22234444          1
> 1      2  3   4          1
> 1      2  3   4          1
> 1      22234444          1
> 1                        1
> 11111111111111111111111111
> 
> MP: tags natural=forest
> Way 1: role=outer
> Way 2: role=inner, natrual=scrub
> Way 3: role=inner, natrual=scrub
> Way 4: role=inner, natrual=scrub
> 
> It seems to be allowed to have 2+3 and 3+4 as inner polygons in the mp. 
> In this case way 3 would have to be added twice to the mp.
> 
> I think we can ignore such a case but we should keep it in mind.
> 
> WanMil
> 
> 
>> HI Marko,
>>
>> I agree that this should be flagged.
>> I tried it with the data for Netherlands and I see no other problems
>> besides the one
>> in my example, so it doesn't see to happen that often.
>>
>> Attached small patch changes mkgmap so that repeated
>> elements are ignored (the first one is used, ignoring differences in
>> roles)
>>
>> If I hear no complains I will commit it next weekend.
>>
>> Gerd
>>
>>  > Date: Sun, 19 Jan 2014 00:16:15 +0200
>>  > From: 

> marko.makela@

>>  > To: 

> mkgmap-dev at .org

>>  > Subject: Re: [mkgmap-dev] type=multipolygon relations
>>  >
>>  > On Sat, Jan 18, 2014 at 10:58:58PM +0100, Minko wrote:
>>  > >Good luck for correcting them, there are tons of those faulty mp's
>> all
>>  > >over the place in NL's ;-)
>>  > >I wouldnt spend too much time for this, better ignore it.
>>  >
>>  > I have found the existing multipolygon and coastline warnings very
>>  > useful. The check for duplicate member ID in a multipolygon relation
>> is
>>  > cheap and has to be done anyway. There is really no good reason not to
>>  > warn about them.
>>  >
>>  > By default, the log output is not enabled. You have to specify
>>  > -Dlog.config=logging.properties in order to enable the diagnostic.
>> Even
>>  > after doing so, you could filter out these particular messages either
>> by
>>  > grep -vf or by configuring the logging.properties file appropriately.
>>  >
>>  > Marko
>>  > _______________________________________________
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>>  > 

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>>
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