[OSM-talk] Graphical generation of Garmin maps from OSM data

[Martin Spott]

Kristian Thy wrote:

> A .osm file contains a lot of MULTILINEs. But in actual fact, some of
> these MULTILINES are actually POLYGONs - lakes and parks and stuff. What
> I'm unsure of is if one input file can contain both 2D geometries line
> lines and 3D geometries like polygons. I know shapefiles are either-or,
> but I'm not aware whether this is a general limitation or something
> specific to shapefiles.

I already _did_ store different types inside a PostGIS table (only
accidentially, afterwards I put some constraints onto the table) and I
remember this stuff came out of a shapefile. So I'm pretty convinced
that it's possible to store objects of different geometry type inside a
single shapefile.

Technically this should work, but for the sake of 'hygiene' in your
data model you might want to prevent such cases, say by separating
lakes into a single layer/file and roads into a different one. During
later use of this data you might face unexpected results when running
queries on these geometries in the case of storing different types in a
single file/layer,

Martin.
-- 
 Unix _IS_ user friendly - it's just selective about who its friends are !
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