[OSM-dev] [OSM-talk] Polygons and Multipolygons

Robert (Jamie) Munro rjmunro at arjam.net
Fri Feb 15 00:28:21 GMT 2008

Hash: SHA1

Artem Pavlenko wrote:
| On 8 Feb 2008, at 11:50, Frederik Ramm wrote:
|> Hi,
|>> I found the way term 'Multipolygon' is used in OSM context is
|>> confusing.
|> True. What we had been looking for was a term for "polygons with
|> holes"; it seemed unreasonable to create a relation "type=polygon"
|> as plain polygons, without holes, don't require relations. But
|> multipolygon is somewhat of a misnomer.
|>> Shouldn't we be calling MultiPolygon  Polygon?
|> There are only 2788 in the database so it would not be too hard to
|> change. I wanted to automatically add the "inner" and "outer" flags
|> to the existing polygons anyway, although they're not strictly
|> required they would make processing easier for some.
| I think having 'outer' and 'inner' flags/tags will help at the data
| entry stage as well.

Can't we use clockwise / anticlockwise rules? The colour is on the
right, therefore polygons run clockwise, holes run anti-clockwise,
islands inside those holes run clockwise again. Under this model, the
sea is a (normally blue coloured) polygon, and the land is a hole in the
sea. AFAICT, this is how it is drawn by the renderers at the moment (the
land colour is just the default rendering background colour).

Robert (Jamie) Munro
Version: GnuPG v1.4.6 (Darwin)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org


More information about the dev mailing list