[postgis-users] st_union(rast) returning null because of non alignment,
Rhys A.D. Stewart
rhys.stewart at gmail.com
Thu Nov 8 09:23:47 PST 2012
Oh the joys of mailing lists!!!
Thanks Pierre, exactly what was required.
All the best,
Rhys
On Thu, Nov 8, 2012 at 11:44 AM, Pierre Racine
<Pierre.Racine at sbf.ulaval.ca>wrote:
> So displaying the two extents it is clear that the two rasters are not
> aligned on the same grid. You will have to ST_SnapToGrid() one raster to
> the other before ST_Union()ing them.
>
> Pierre
>
> > -----Original Message-----
> > From: postgis-users-bounces at lists.osgeo.org [mailto:postgis-users-
> > bounces at lists.osgeo.org] On Behalf Of Rhys A.D. Stewart
> > Sent: Thursday, November 08, 2012 6:50 AM
> > To: PostGIS Users Discussion
> > Subject: Re: [postgis-users] st_union(rast) returning null because of non
> > alignment,
> >
> > So given that st_union is not the solution, how would I go about merging
> two
> > adjacent raster tiles?
> >
> >
> > On Wed, Nov 7, 2012 at 6:12 PM, Rhys A.D. Stewart <
> rhys.stewart at gmail.com>
> > wrote:
> >
> >
> > ok, well that may be the issue, I was trying to union a rasterised
> table of
> > adjacent polygons. So will the corners may touch I doubt they overlap,
> but here
> > is the output of st_metadata for two of the polygons that are adjacent:
> >
> > Clarendon 698486.043582936 617384.893096908 153 229 250 250 0 0
> > 3448 4
> > Manchester 683177.872077352 632613.85425893 117 182 250 250 0 0
> > 3448 4
> >
> >
> >
> > On Wed, Nov 7, 2012 at 6:01 PM, Pierre Racine
> > <Pierre.Racine at sbf.ulaval.ca> wrote:
> >
> >
> > By "on the same grid" I mean " at least one of any of the
> four
> > corners of any pixel of one raster falls on any corner of the grid of
> the other
> > raster" as stated in the ST_SameAlignment() doc.
> >
> > What is (are) the pixel size?
> >
> >
> > > -----Original Message-----
> > > From: postgis-users-bounces at lists.osgeo.org [mailto:
> postgis-
> > users-
> > > bounces at lists.osgeo.org] On Behalf Of Rhys A.D. Stewart
> >
> > > Sent: Wednesday, November 07, 2012 5:51 PM
> > > To: PostGIS Users Discussion
> >
> > > Subject: Re: [postgis-users] st_union(rast) returning
> null
> > because of non
> > > alignment,
> > >
> > > Pierre,
> > >
> > > If by on the same grid you mean equal, then no hey are
> not.
> > Here they are.
> > >
> > >
> > > 1: POLYGON((766242.610093044
> > 641994.463110607,779742.610093044
> > > 641994.463110607,779742.610093044
> > 648494.463110607,766242.610093044
> > > 648494.463110607,766242.610093044 641994.463110607))
> > > 2:POLYGON((698486.043582936
> > 617384.893096908,736736.043582936
> > > 617384.893096908,736736.043582936
> > 674634.893096908,698486.043582936
> > > 674634.893096908,698486.043582936 617384.893096908))
> > >
> > > Thanks,
> > >
> > > Rhys
> > >
> > >
> > > On Wed, Nov 7, 2012 at 5:40 PM, Pierre Racine
> > <Pierre.Racine at sbf.ulaval.ca>
> > > wrote:
> > >
> > >
> > > Hi Rhys,
> > >
> > > Both rasters must also have their upperlefx and
> upperlefty
> > on the same
> > > grid.
> > >
> > > Could you do:
> > >
> > > SELECT ST_AsText(ST_ConvexHull(rast))
> > >
> > > on both rasters and post the result here?
> > >
> > > Thanks,
> > >
> > > Pierre
> > >
> > >
> > > > -----Original Message-----
> > > > From: postgis-users-bounces at lists.osgeo.org
> > [mailto:postgis-users-
> > > > bounces at lists.osgeo.org] On Behalf Of Rhys A.D.
> > Stewart
> > > > Sent: Wednesday, November 07, 2012 5:33 PM
> > > > To: PostGIS Users Discussion
> > > > Subject: [postgis-users] st_union(rast)
> returning null
> > because of non
> > > alignment,
> > > >
> > > > Greetings,
> > > >
> > > > according to the trusty docs online two rasters
> are
> > aligned when they
> > > share the
> > > > same skew, scale and srid. Created a raster using
> > st_asraster and
> > > according to
> > > > st_metadata scale, skew and srid are all equal.
> Howvere
> > st_unon
> > > complains
> > > > saying that 'The two rasters provided do not
> have the
> > same alignment.
> > > > Returning NULL'
> > > >
> > > > I noticed that ticket #1336 as possibly
> relating to my
> > issue, but I'm not
> > > entirely
> > > > sure. My posgis version is:
> > > > POSTGIS="2.0.0 r9605" GEOS="3.3.3-CAPI-1.7.4"
> > PROJ="Rel. 4.8.0, 6
> > > March
> > > > 2012" GDAL="GDAL 1.9.0, released 2011/12/29"
> > LIBXML="2.7.8"
> > > > LIBJSON="UNKNOWN" TOPOLOGY RASTER
> > > >
> > > >
> > > > What am I missing or doing incorrectly?
> > > >
> > > > Regards,
> > > >
> > > > Rhys
> > >
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> > >
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