[OSM-dev] What exactly is a polygon?

Till Harbaum lists at harbaum.org
Thu Nov 6 08:04:01 GMT 2008


Hi,

i am still not sure i fully understand when exactly a way
a polygon is. What i've learned so far:

If the first and the last node of a way are identical then the
way is a polygon, except it's tagged highway, waterway or
railway.

What's the purpose of the area tag? Does it make a way
a polygon, even if the first and last node are not identical?
Is it used to make highways/waterways or railways a polygon?

Should my tool automatically tag a way an area if the first
and last node are identical?

What about more complex shapes? What if e.g. the first and
a node in the middle are identical? Is this is polygon with a "tail"?

Till




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