[postgis-users] Raster tile size impact results
Pierre Bails
bails at getredbird.com
Mon Aug 22 01:07:56 PDT 2016
Hi Pierre,
I have the same problem with or without the rescale function...
--
Pierre Bails
Le mar. 9 août 2016 à 14:30, Pierre Racine <Pierre.Racine at sbf.ulaval.ca> a
écrit :
> What if you remove the ST_Rescale() ?
>
> > -----Original Message-----
> > From: postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] On
> Behalf
> > Of Pierre Bails
> > Sent: Thursday, July 28, 2016 4:28 AM
> > To: PostGIS Users Discussion <postgis-users at lists.osgeo.org>
> > Subject: Re: [postgis-users] Raster tile size impact results
> >
> > Hi,
> >
> > The full request is :
> >
> > SELECT DISTINCT ST_AsGeojson(ST_Union((px.geom),4326))
> > FROM (
> > SELECT *
> > FROM dsm
> > INNER JOIN
> > ST_SetSRID(ST_MakeValid(ST_GeomFromGeojson('{"type":"Polygon","coordinat
> > es":[[[],[],[],[],[],[]]]}')), 4326) AS geom on ST_Intersects(dsm.rast,
> geom)
> > ) AS inter,
> > ST_PixelAsCentroids (ST_Clip(ST_Rescale(inter.rast, 0.5), inter.geom),1)
> as px
> >
> >
> > Thanks,
> >
> > Pierre
> >
> > --
> >
> > Pierre Bails
> > GIS Engineer
> >
> >
> > Redbird
> > EMEA - 16, rue de la Comète - 75007 Paris - France
> > US - 44 Tehama St, San Francisco, CA 94105 - USA
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> 184 165
> > 201
> >
> > bails at getredbird.com <mailto:bails at getredbird.com> | www.getredbird.com
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> >
> > Le lun. 25 juil. 2016 à 21:30, Pierre Racine <
> Pierre.Racine at sbf.ulaval.ca
> > <mailto:Pierre.Racine at sbf.ulaval.ca> > a écrit :
> >
> >
> > I will need to see your last query to try to find the problem.
> >
> >
> >
> > Pierre
> >
> >
> >
> > From: postgis-users [mailto:postgis-users-bounces at lists.osgeo.org
> > <mailto:postgis-users-bounces at lists.osgeo.org> ] On Behalf Of Pierre
> Bails
> > Sent: Wednesday, July 20, 2016 5:36 AM
> >
> >
> > To: PostGIS Users Discussion <postgis-users at lists.osgeo.org
> > <mailto:postgis-users at lists.osgeo.org> >
> > Subject: Re: [postgis-users] Raster tile size impact results
> >
> >
> >
> > Hi,
> >
> >
> >
> > Thank you for the tips.
> >
> >
> >
> > Well, I don't know why, but the st_clip function doesn't seem work
> fine.
> >
> > After clipping and dumping each pixel as point, some points follow
> tiles,
> > others follow the geometry. Any idea why ?
> >
> > For now, to avoid the problem, I apply a St_ContainsProperly after
> the
> > dump.
> >
> >
> >
> >
> >
> >
> > Red : geometry
> >
> > Light blue : tiles
> >
> > Dark blue : pixels as points
> >
> >
> >
> > Thank you for your help !
> >
> >
> >
> > Pierre
> >
> >
> >
> >
> >
> > Le ven. 15 juil. 2016 à 17:28, Pierre Racine <
> Pierre.Racine at sbf.ulaval.ca
> > <mailto:Pierre.Racine at sbf.ulaval.ca> > a écrit :
> >
> > Sorry for the late answer.
> >
> > You have to vectorize them on the fly from within OpenJump:
> >
> > SELECT (ST_DumpAsPolygons(rast).* FROM yourrastertable;
> >
> > If your raster is very big and tiled, just vectorize the
> tiles you
> > need:
> >
> > SELECT rid, rast::geometry FROM yourrastertable;
> >
> > Look at the rids and then:
> >
> > SELECT (ST_DumpAsPolygons(rast).* FROM yourrastertable
> > WHERE rid = x or rid = y
> >
> > Pierre
> >
> > > -----Original Message-----
> > > From: postgis-users [mailto:postgis-users-
> > bounces at lists.osgeo.org <mailto:postgis-users-bounces at lists.osgeo.org>
> ] On
> > Behalf
> > > Of Pierre Bails
> > > Sent: Friday, June 24, 2016 12:32 PM
> > > To: PostGIS Users Discussion <
> postgis-users at lists.osgeo.org
> > <mailto:postgis-users at lists.osgeo.org> >
> > > Subject: Re: [postgis-users] Raster tile size impact
> results
> > >
> > > Hello,
> > >
> > > Unfortunatly, I don't find a way to print raster results
> in
> > OpenJump. Can you
> > > explain me how I can do it ?
> > >
> > > Thank you for your help !
> > >
> > > Pierre
> > >
> > > Le lun. 20 juin 2016 à 16:16, Pierre Racine
> > <Pierre.Racine at sbf.ulaval.ca <mailto:Pierre.Racine at sbf.ulaval.ca>
> > > <mailto:Pierre.Racine at sbf.ulaval.ca
> > <mailto:Pierre.Racine at sbf.ulaval.ca> > > a écrit :
> > >
> > >
> > > I would try to understand, visually using
> OpenJump, how
> > your tiles are
> > > clipped in the two cases... I guess sometimes 1 pixel
> wide tiles
> > get clipped in a
> > > strange way.
> > >
> > > Pierre
> > >
> > > > -----Original Message-----
> > > > From: postgis-users [mailto:postgis-users-
> > bounces at lists.osgeo.org <mailto:postgis-users-bounces at lists.osgeo.org>
> > > <mailto:postgis-users-bounces at lists.osgeo.org
> > <mailto:postgis-users-bounces at lists.osgeo.org> > ] On Behalf
> > > > Of Pierre Bails
> > > > Sent: Wednesday, June 15, 2016 11:41 AM
> > > > To: postgis-users at lists.osgeo.org <mailto:
> postgis-
> > users at lists.osgeo.org> <mailto:postgis- <mailto:postgis->
> > > users at lists.osgeo.org <mailto:users at lists.osgeo.org> >
> > > > Subject: [postgis-users] Raster tile size impact
> results
> > > >
> > > > Hi all,
> > > >
> > > > I'm looking for get all pixel's value in a
> raster insert
> > thanks to
> > > raster2pgsql
> > > > intersect by a polygon.
> > > > Nevertheless, there are some things that I don't
> > understand: depends
> > > on tile
> > > > size, I don't have the same result... The error
> between 2
> > raster is also
> > > correlate
> > > > to the pixel size (I assume it's due to the
> pixel number).
> > > >
> > > > Can you explain me how the tile size can
> influence the
> > final result ?
> > > >
> > > > Here is the query :
> > > > SELECT DISTINCT SUM((px).val)
> > > > FROM(
> > > > SELECT *
> > > > FROM mns INNER JOIN
> > > >
> > >
> >
> st_setsrid(st_geomfromgeojson('{"type":"Polygon","coordinates":[[[x,y],[x,y],[x
> > > > ,y] ]]}'), 4326) as geom on
> ST_Intersects(mns.rast, geom)
> > > > ) AS clip, ST_PixelAsCentroids
> (ST_Clip(clip.rast,
> > clip.geom),1) AS px;
> > > >
> > > >
> > > > DSM px size 70cm:
> > > > raster2pgsql -a -t 250x250 -s 4326 -F
> pathToDSM.tiff
> > dsmTable (result:
> > > 46 347
> > > > 846)
> > > >
> > > > raster2pgsql -a -t 50x50 -s 4326 -F
> pathToDSM.tiff
> > dsmTable : 46 382
> > > 873
> > > > Difference: 35027
> > > >
> > > >
> > > > DSM px size 20cm :
> > > > raster2pgsql -a -t 250x250 -s 4326 -F
> pathToDSM.tiff
> > dsmTable : 567
> > > 505 888
> > > >
> > > > raster2pgsql -a -t 50x50 -s 4326 -F
> pathToDSM.tiff
> > dsmTable : 596
> > > 897 610
> > > > Difference: 29 391 722
> > > >
> > > >
> > > > If we considere 250x250's result as reference,
> there is a
> > difference of
> > > 0.07% in
> > > > the first case, and 5% in the second. If the
> polygon area
> > increases, the
> > > error rate
> > > > increases.
> > > >
> > > > Thank you,
> > > >
> > > > Pierre
> > > _______________________________________________
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> > users at lists.osgeo.org> >
> > >
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> >
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