Hi,
1. Does st_touches not work for that ?
2. What do you mean by below ? south from the line ? St_distance should help
you to find the closer one from Q.
Hugues.
Message d'origine
De: postgis-users-boun...@postgis.refractions.net de la part de Ed Linde
Date: lun. 29/10/2012
On 29 October 2012 21:33, Ed Linde edoli...@gmail.com wrote:
Hi All,
I need help with 2 hard problems. I store triangles in a table as POLYGON.
1. I want to know for a given triangle, which triangles share an edge
(adjacent) with this triangle.
Sounds like you have a finite element mesh with
Hi All,
Thanks for the suggestions.
For 1) I will look into how ST_touches works and see if it can pick up all
the adjacent polygons to
the one I have. And also look into Mike's suggestion on ST_relate...though
I must admit it looks
more complex.
For 2) I will try to clarify it a bit more... its
Hi All,
Wondering if that diagram made things any simpler or is it still not clear
what the problem
is?
Thanks,
Ed
On Mon, Oct 29, 2012 at 11:57 AM, Ed Linde edoli...@gmail.com wrote:
Attached is a figure. Where the dotted line is the boundary of the voronoi
cell whose
generator is point P1.
Yes indeed it's clearer.
You could compute the distance between each adjacent triangle and the
voronoi generator and order by shortest distance. (taking the
triangle's centroid for the distance)
Also, is the voronoi boundary forming a polygon or just a line ? in
the former, you could find all the
Hi Ed,
Well if clarifies one thing at least, you can ignore Mike's st_Relate
because 5 is not adjacent to a linear edge, it is only adjacent to a
vertex, so st_touches should work fine.
so you are looking for:
1. a specific triangle by id
2. that intersects triangle VC
3. and the triangles
Hi All,
I was trying to do this intersection between two tables, I have inserted
the selects for the two tables and the error. Also the postgis full version
information.
Is there a way to get around this problem? Is this a bug? The polygons in
both tables contain 3D points. Could this be a
If the points are computed in the right order, you can store them and
pass them to st_makeLine and st_makePolygon.
If not, you can form a segment between 2 closest points and connect it
to the closest points.
On 29 October 2012 15:37, Ed Linde edoli...@gmail.com wrote:
Hi All,
Thanks for the
Thanks Nicolas. Just about the error, is this because the line segments are
too close
and postgis 2.0 could not handle this? If so is there a workaround, even if
it means
slightly having to perturb each point's position to not run into this bug.
I was really hoping that the intersection of two
Hi,
No. this is because some of your polygons are not valid:
for instance:
select st_isvalid('POLYGON ((593921 5219610 803,593921 5219610
818,593921 5219620 818,593921 5219620 803,593921 5219610
803))'::geometry);
NOTICE: Too few points in geometry component at or near point 593921
5219610 803
Thanks Nicolas! Will look at the script that generated the polygon text..
must have goofed something up there.
On Mon, Oct 29, 2012 at 4:05 PM, Nicolas Ribot nicolas.ri...@gmail.comwrote:
Hi,
No. this is because some of your polygons are not valid:
for instance:
select st_isvalid('POLYGON
Yes, it looks like some points were not put in the right order before
building a polygon, thus these butterfly polygons you generated.
If the formed polygon are expected to be convex, you could use
st_convexhull on the point cloud to generate the polygons.
On 29 October 2012 16:09, Ed Linde
Ok thanks, will look into that function. Because I wonder if the s/w I am
using is
actually outputting the vertices of each face in a cyclical fashion or just
arbitrarily.
Cheers,
Ed
On Mon, Oct 29, 2012 at 4:23 PM, Nicolas Ribot nicolas.ri...@gmail.comwrote:
Yes, it looks like some points
Hi Nicolas,
It seems like sometimes the points are one and the same and I get
linestrings and not
actual polygons. I pass these points in from a perl script, so is there a
way I can just
give the raw x,y,z coordinates of these points and do a st_convexhull
function on them?
Could you please give
You should filter out the consecutive points. If there are more than 2
points, you can then call st_convexHull() on the point set:
with points as (
select 'POINT (0 0)'::geometry as geom
UNION
select 'POINT (1 0)'::geometry as geom
UNION
select 'POINT (1
I tried something like the following without removing the same points ad it
seems to work:
SELECT st_astext(ST_ConvexHull(ST_GeomFromText('MULTIPOINT(593901 5219610
814,593901 5219610 814,593899 5219610 814,593899 5219610 814,593901 5219610
814)')));
LINESTRING Z (593901 5219610 814,593899
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