I tried reversing the test and I'm still having the same problem. Here is
some information I got from pgadmin3 concerning my tables:
CREATE TABLE sf_quat_geopy
(
gid serial NOT NULL,
sf_quat_ numeric,
sf_quat_id numeric,
ptype character varying(35),
name character varying(200),
liq ch
If you are running 8.3, I think since we don't have our costs set for spatial
functions, the ST_Intersects may be taking higher priority than the other
conditions because you have it listed first.
Try doing
SELECT
ST_Intersection(GeoB.the_geom,GeoQ.the_geom) as intersect_geom,
GeoB.*,
My bad, you're both correct. If that's the case, what does the
ST_ExteriorRing function produce? When I test it I get "geom is not a polygon".
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Ramsey
Sent: Friday, October 24, 2008 2:59 PM
To: Post
Lee
I think a minimum enclosing circle might also be larger than the
polygon. Think of a circle circumscribing a square. However I think
you are right in needing a circle. A district that is an elongated
rectangle (could be a severely gerrymandered district) would have a
ratio of 1 if the c
It's an inscribed circle? I thought it was a containing one.
P.
On Fri, Oct 24, 2008 at 12:50 PM, Lee Meilleur <[EMAIL PROTECTED]> wrote:
>
>
> The area of the convex hull is actually larger than the area of the polygon,
> so the ratio ends up being greater than 1. With the Roeck test, the rati
The area of the convex hull is actually larger than the area of the polygon, so
the ratio ends up being greater than 1. With the Roeck test, the ratio will
always be between 0 and 1, with a compact polygon approaching 1 (the area of
the inner circle approaching the area of the polygon). A ra
You're query looks good. Do you have GIST indexes on the geometries in
both tables?
What is the result of EXPLAIN?
-- Kevin
Bob and Deb wrote:
Hello All,
I'm new to postgis and need help with (what seems to be a simple) query.
I have 2 geology maps that overlap at a corner:
Yeah, it's a relatively newly discovered syntax that works very well.
http://postgis.refractions.net/documentation/manual-svn/ST_Dump.html
Cheers,
Kevin
Frank Durstewitz, Emporis GmbH wrote:
Hi Kevin,
yes, that looks good. I was on that way, but could not figure out, how
to get the geometry
Hello All,
I'm new to postgis and need help with (what seems to be a simple) query.
I have 2 geology maps that overlap at a corner:
| |
| |
| -|--
| ||
Hi Kevin,
yes, that looks good. I was on that way, but could not figure out, how
to get the geometry out of the dump rows.
Very nice this one, i have never seen this ".geom" (and still could not
find it somewhere in the docs?).
Many thanks!
Kindly regards, Frank
Kevin Neufeld am 24.10.2008 2
And taking some smart drugs might even help with implementing the
algorithm 8^)
Pedro Doria Meunier wrote:
Bruce,
You're absolutely right ;-)
Regards
___
postgis-users m
What about something like this:
SELECT ST_Collect(geom)
FROM (
SELECT (ST_Dump(geom)).geom
FROM my_multi_polygon_table) AS foo
WHERE ST_Y(ST_Centroid(geom)) <= 0;
Explode the multipolygon into individual polygons using ST_Dump, and
ST_Collect the ones back up again where the centroid falls
Bruce,
You're absolutely right ;-)
Regards
--
Pedro Doria Meunier <[EMAIL PROTECTED]>
On Fri, 2008-10-24 at 12:25 -0600, Bruce Rindahl wrote:
> After a quick look at the links, couldn't a stored procedure
> (function) be used here? I envision the input is a polygon, grab the
> outside rin
After a quick look at the links, couldn't a stored procedure (function)
be used here? I envision the input is a polygon, grab the outside ring,
explode the vertices's to get a set of points(all existing functions).
Then the collection of points could be looped through with the algorithm
descr
> I forgot to mention one point: the point and the polygon tables reside in
> different databases and dblink is used for cross db query. Today, we
> imported the small table into the db where the polygon table is and the
> problem is gone. So it sounds like dblink might be the reason for the
> cras
Hello list,
i must remove from multipolygon some polygons, for example remove all
polygons from "russia", where latitude of centroid of polygon is <= 0
(in this case the part of russia which is near alaska).
I think this should be possible (ST_Dump...), but i cannot find any way
to do so.
D
This page has a nice write-up of three different algorithms. Go Paul!
http://www.personal.kent.edu/~rmuhamma/Compgeometry/MyCG/CG-Applets/Center/centercli.htm
Paul Ramsey wrote:
Wouldn't the ratio of area to perimeter be a similar metric? Also,
wouldn't it be easier to just stop letting politi
Yes and yes to both questions, but the Roeck test is required by some states.
And some states don't allow their politicians to draw their political
boundaries.
Thanks Martin, I'll test the convex hull and compare with the Roeck from our
commercial software.
Brent, thanks for the link, not su
Wouldn't it be easier and more accurate to use the convex hull of the
polygon instead of the minimum enclosing ball? The CH will have smaller
area (i.e. be a tighter bound on the area covered by the polygon), so it
seems like it would give a more accurate basis for comparison.
Lee Meilleur wro
Funny, I was just doing some web surfing to find the algorithm for a Minimum
Bounding Rotated Rectangle and came across this:
http://geometryalgorithms.com/Archive/algorithm_0107/algorithm_0107.htm
Brent
Paul Ramsey wrote:
Wouldn't the ratio of area to perimeter be a similar metric? Also,
wo
Wouldn't the ratio of area to perimeter be a similar metric? Also,
wouldn't it be easier to just stop letting politicians draw their own
boundaries? :)
I wonder what the algorithm for minimum enclosing circle is...
(Short answer, no, because we don't have a min-circle routine.)
P.
On Fri, Oct 2
We continue to inch closer to a 1.3.4 release. Please compile and test
1.3.4rc2, available from
http://postgis.refractions.net/download/postgis-1.3.4rc2.tar.gz
Thanks!
Paul
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http://pos
Has anyone calculated the Roeck test using PostGIS? This is an area based
measure that computes the ratio of the area of a polygon to the area of the
minimum enclosing circle for the polygon. It's used to measure compactness of
districts for redistricting applications, basically a way to tes
> >
> > Quale è il motivo per cui ho pensato ST_Boundary è stato il più
> > vicino. Parlando in una lingua diversa e con google traduttore è
> > divertente. Dovremmo farlo più spesso.
> >
> > Per oratori italiani - è questa la traduzione davvero
> comprensibile o
> > faccio a suonare come un
Hello,
Is there is a possibility now to store raster data in postgis. if not when this
will be possible
Thanks
Ihab
_
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> Obe, Regina wrote:
> > Chris,
> >
> > Ho pensato che si riferisse a questa funzione
> >
> http://youngcow.net/doc/oracle10g/appdev.102/b14255/sdo_util.h
> tm#BJEIGJIE
> >
> > Quale è il motivo per cui ho pensato ST_Boundary è stato il più
> > vicino. Parlando in una lingua diversa e con goo
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