[Freegis-list] shapelib question

[Timothy H. Keitt]

Yes, that's a good point.  I do know about the FMaps project.  To my knowledge, they
are not using the postgresql built-in geometry types, but are simply implementing
2-3D point types, but I'll check.

Cheers,
Tim

Adrian Custer wrote:

> You might write the folks on the FMaps project (sourceforge). They have
> spent the better part of the last years working to develop the
> PostgreSQL geographic data types and should be able to help you.
>
> --adrian
>
> On 06 Apr 2001 11:28:52 -0400, Timothy H. Keitt wrote:
> > Frank Warmerdam wrote:
> >
> > >
> > > Multi-part polygons may be multiple islands (one feature, but disconnected
> > > outer rings), or one polygon with holes (or a mixture).  In theory you
> > > are supposed to be able to determine this from the winding direction of
> > > the rings (whether they are outer or inner edges) but in practice many
> > > systems don't setup this distinction up properly (like most applications
> > > using Shapelib to write) so you pretty much have to determine yourself.
> > >
> >
> > (O.K. basic geometry here, but bear with me.)  If turning right is negative
> > and turning left is positive, then if the sum of turning angles is negative,
> > the winding direction is clockwise, no?  Is there a convention that inner
> > edges are digitized in a particular direction?
> >
> > My dilema is whether to use an array of polygons in postgresql, or to use a
> > seperate table with multiple entries corresponding to a given "shape."  I don't
> > know if postgesql polygons can contain (or understand) holes or not.
> >
> > Tim
> >
> > --
> > Timothy H. Keitt
> > Department of Ecology and Evolution
> > State University of New York at Stony Brook
> > Phone: 631-632-1101, FAX: 631-632-7626
> > http://life.bio.sunysb.edu/ee/keitt/
> >
> >
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> >

--
Timothy H. Keitt
Department of Ecology and Evolution
State University of New York at Stony Brook
Phone: 631-632-1101, FAX: 631-632-7626
http://life.bio.sunysb.edu/ee/keitt/