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

Nick Black nickblack1 at gmail.com
Fri Dec 22 12:31:05 GMT 2006


On 12/22/06, Kristian Thy <thy at 42.dk> wrote:
>
> On Fri, Dec 22, Martin Spott wrote:
> > OGR is able to handle at least the common geometry types like POINT,
> > LINE, MULTILINE, POLYGON, MULTIPOLYGON - these are the ones _I_ use OGR
> > for, there may be some more.
>
> Yes, I know - sorry for not making myself clear.
>
> 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.



A TAB file can certainly contain mixed geometries, like LINESTRING,
MULTILINESTRING, POLYGON in the same file, which is a bit of a pain when
importing into databases.  An OGC POLYGON  isnt necesserily 3D and and
linestring isnt necesserily 2D and so on.  If an exchange format should make
it easy to shift data from one place to another, probably from one DB to
another, then IMO it should constrain the geometry types, but not
necesserily the Dimensions of the data.

Nick


\\kristian
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-- 
Nick Black
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