[postgis-users] st_union(rast) returning null because of non alignment,

[Rhys A.D. Stewart]

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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