[postgis-users] Creating an ellipse area ?

[Bruce Rindahl]

Flavio
The ellipse is approximated by a series of line seqments.  The last
parameter is number of segments in one quarter of the ellipse.  See the
documentation of buffer.  The default is 8,  you shouldn't need anything
more than about 16 - 100 is way too much.
>From your query the radius of the ellipses are 0.010 (rx) and 0.005 (ry).  I
don't know what units you are using but if this is what you need it should
work.  Note that a.direction should be in radians
Bruce

-----Original Message-----
From: Flavio Perri [mailto:FPERRI at it.ibm.com] 
Sent: Friday, May 18, 2007 8:02 AM
To: rindahl at lrcwe.com; PostGIS Users Discussion
Subject: RE: [postgis-users] Creating an ellipse area ?

Hi, I tried that function, and seems to work fine, but I don't understand
the last parameter (i tried with 1000). Then, a question: I tried to select
all geometries inside the ellipse area with this query:
  select * from pointTable a, linesTable b where id=xxx and
Intersects(b.the_geom, ellipse(X(a.the_geom),Y(a.the_geom),0.010,0.005,
a.direction, 1000) and a.the_geom && l.the_geom

is it right?

Flavio

postgis-users-bounces at postgis.refractions.net wrote on 17/05/2007 17.39.57:

> Flavio
> Look at the ellipse function at:
> http://postgis.refractions.net/support/wiki/index.php?plpgsqlfunctions
>
> Bruce
>
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
Flavio
> Perri
> Sent: Thursday, May 17, 2007 3:14 AM
> To: PostGIS Users Discussion
> Subject: [postgis-users] Creating an ellipse area ?
>
>
> Hi again.
>
> Given a point, is it possible to create an ellipse area starting from it?
>
>
> Flavio Perri
>
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