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osmlab / fixing-polygons-in-osm

Fixing (multi)polygons in OpenStreetMap
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Touching outer rings #30

Open wolfbert opened 7 years ago

wolfbert commented 7 years ago

While touching inner rings are permitted in osm, how about touching outer rings?

JOSM sees this as an error, and it also cannot be handled by OGC conforming functions. These rings are sometimes used in an attempt to group neighbouring buildings (which can usually be expressed in some other way) and sometimes just plain unnecessary,

joto commented 7 years ago

Rules here are the same as for OGC/simple features. Outer rings are never allowed to touch in a line, in that case, just remove that line. Outer rings are allowed to touch in points (think of the figure 8), but the rules are more complex there.

wolfbert commented 7 years ago

It might be helpful to put this in the Wiki examples as well.