[Qgis-user] Re: polygon direction/orientation

[Brad Nesom]

I found this on the esri website. hope it helps...

Calculate for each poly the length and bearing of it's longest heddge

This script is designed to work on polygons having very geometric shapes
(like agricultural fields).

Bearing values : from 0 to 179.99°

0° for N or S;
45° for N-E or S-W;
90° for E or W;
135° for S-E or N-W;

Example of application : determination of the orientation of the sawing
lines in agricultural parcels. We tested it on a sample of a little 100
parcels and we had a correspondence of 84% between observed sawing lines
orientations and predicted orientations. This information may be useful in
radar imagery analysis.

For our other tools : see our web GIS-TOOLS site at :
http://www.mila.ucl.ac.be/logistique/sig/sig-tools/

On Wed, Oct 13, 2010 at 12:20 PM, Mike Toews <mwtoews at gmail.com> wrote:

> It is possible to do this from a low-level environment. GEOS and JTS
> have a MinimumDiameter function that effectively finds the minimum
> axis of elongation and returns it as a linestring. You only need to
> take the normal angle of the resulting linestring. There is also a
> related MinimumRectangle function that puts the smallest rectangle on
> your polygon.
>
> -Mike
>
> On 13 October 2010 10:09, Carson Farmer <carson.farmer at gmail.com> wrote:
> > Well I'm still not exactly sure it is you want, but I'm fairly sure there
> > isn't a plugin to do this sort of thing. You could certainly do this from
> > the Python console, or the other option would be to convert your polygons
> to
> > lines, then use the azimuth tool on those lines?
> > Carson
> >
> > On 13 October 2010 17:29, simogeo <simon.georget at gmail.com> wrote:
> >>
> >> Hi Carson,
> >>
> >> I call it azimuth but don't give too much importance to the terminology.
> I
> >> just want to know the angle from North And South axis.
> >>
> >> http://osgeo-org.1803224.n2.nabble.com/file/n5631658/azi.jpg
> >>
> >>
> >> Keep it simple with a rectangle for now (forget complex shape)
> >>
> >>
> >>
> >> --
> >> View this message in context:
> >>
> http://osgeo-org.1803224.n2.nabble.com/polygon-direction-orientation-tp5631577p5631658.html
> >> Sent from the qgis-user mailing list archive at Nabble.com.
> >> _______________________________________________
> >> Qgis-user mailing list
> >> Qgis-user at lists.osgeo.org
> >> http://lists.osgeo.org/mailman/listinfo/qgis-user
> >
> >
> >
> > --
> > Carson J. Q. Farmer
> > ISSP Doctoral Fellow
> > National Centre for Geocomputation
> > National University of Ireland, Maynooth,
> > http://www.carsonfarmer.com/
> >
> > _______________________________________________
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> > Qgis-user at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/qgis-user
> >
> >
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