[OSM-dev] Shared borders of (multi) polygons represented as duplicated ways

Jochen Topf jochen at remote.org
Mon Nov 24 17:29:38 UTC 2014


On Fri, Nov 21, 2014 at 11:57:47AM -0800, Paul Norman wrote:
> On 11/21/2014 10:09 AM, Stefan Baebler wrote:
> >From the bugfix perspective it should probably be one more step of merging
> >(eg MergeWays()) after two prior merges (mergePoints() and
> >mergeWayPoints()).
> Yes - and this shouldn't be too computationally expensive, as there aren't
> that many ways, at least compared to points.

I am not sure this is enough. We might have to split up linestrings, too. Say
you have something like this:

    A---B
    |   |
    D---C
    |   |
    E---F

with linestrings A-B-C-D-A and D-C-F-E-D. In this simple case two closed ways
with the same nodes as those linestrings is fine, ie both using the nodes D and
C. But in a more complex case with more nodes and maybe some other lines
involved, we probably want two multipolygons which share a way D-C (and have
separate ways D-A-B-C and D-E-F-C, respectively), don't we? But then we have
to split up those linestrings.

Jochen
-- 
Jochen Topf  jochen at remote.org  http://www.jochentopf.com/  +49-173-7019282



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