[mkgmap-dev] shape merger in high-prec-coord branch

Sat Jan 18 17:00:17 GMT 2014

Hi WanMil,

I see that shapes created from precompiled sea are merged,
so it works in general. The problem remains that
for low resolutions I have to merge the shapes before the coords are 
rounded. So, for low resolutions the shape merger stops
too early, because it will not create shapes with > 250 points
as long as we use the java.awt.geom.area to split those
shapes, and the merger doesn't know the result of the RoundCoordsFilter
which typically reduces the number of points drastically for low res.

Gerd

> Date: Thu, 16 Jan 2014 12:09:17 -0800
> From: gpetermann_muenchen at hotmail.com
> To: mkgmap-dev at lists.mkgmap.org.uk
> Subject: Re: [mkgmap-dev] shape merger in high-prec-coord branch
> 
> Hi WanMil,
> 
> yes, a few more shapes were be merged because of this change.
> Only if the parts go into different sub divisions they are not merged.
> I am not sure if that works for precompiled sea data, I'll 
> verify that tomorrow.
> 
> Gerd
>  
> 
> WanMil wrote
> > Hi Gerd,
> > 
> > good! This is the first part of my idea.
> > Additionally I thought about what you have written as TODO: maybe better 
> > merge here? I think when cutting multipolygons it often happens that 
> > there are parts cut off that needn't be cut.
> > I have attached a screenshot of a sea tile where I have colored some 
> > polygons in blue that could be merged to one big polygon. Maybe there is 
> > an advantage that some of the small cuts do not disappear on lower zoom 
> > levels because they belong to a bigger polygon.
> > 
> > But I am not sure if that isn't already solved by your changes.
> > 
> > WanMil
> > 
> >> Hi WanMil,
> >>
> >> please check the changes in r2970 reg. MultiPolygonRelation.
> >> Is this the change you had in mind?
> >>
> >> Gerd
> >>
> >>  > Date: Wed, 15 Jan 2014 21:55:17 +0100
> >>  > From: 
> 
> > wmgcnfg@
> 
> >>  > To: 
> 
> > mkgmap-dev at .org
> 
> >>  > Subject: Re: [mkgmap-dev] shape merger in high-prec-coord branch
> >>  >
> >>  >
> >>  > > I think the artifacts are created by the rounding that happens
> >>  > > when we convert from or to java.awt.geom.Area.
> >>  >
> >>  > Yes. After the multipolygon splitting only the first and the last
> >> point
> >>  > of a common edge of two polygons can be a point that is added
> >>  > artificially. It sounds possible to detect if it ca be removed.
> >>  >
> >>  > WanMil
> >>  > _______________________________________________
> >>  > mkgmap-dev mailing list
> >>  > 
> 
> > mkgmap-dev at .org
> 
> >>  > http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
> >>
> >>
> >> _______________________________________________
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> 
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> > 
> > 
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> > 
> > mp_merge.png (16K)
> > &lt;http://gis.19327.n5.nabble.com/attachment/5793366/0/mp_merge.png&gt;
> 
> 
> 
> 
> 
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