[postgis-users] Finding highest cell value in raster using ST_Value
Pierre Racine
Pierre.Racine at sbf.ulaval.ca
Mon Jun 25 14:41:26 PDT 2012
But try
SELECT ST_Centroid((ST_PixelAsPolygons(ST_Reclass(rast))).geom)
FROM yourRaster
and let us know the difference in terms of performance... You could be surprised!
Pierre
> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-
> bounces at postgis.refractions.net] On Behalf Of e.j.h.polle
> Sent: Monday, June 25, 2012 5:34 PM
> To: postgis-users at googlegroups.com
> Cc: PostGIS Users Discussion
> Subject: Re: [postgis-users] Finding highest cell value in raster using ST_Value
>
> Hi Bborie, Pierre,
>
>
> Thanks for adding the ticket. (http://trac.osgeo.org/postgis/ticket/1889)
>
> And I guess I am looking forward to PostGIS 2.1 then :-) (But I am still a little
> proud of my 'round-about way' to locate the cell with the highest value...)
>
> Cheers,
>
>
> Egge-Jan
>
>
> Op maandag 25 juni 2012 21:39:29 UTC+1 schreef Bborie Park het volgende:
>
> Too many columns. I was thinking that this is better served in a
> separate function as that value could be repeated. I'm adding a ticket
> for that separate function.
>
> On 06/25/2012 01:36 PM, Pierre Racine wrote:
> > Good find Bborie!
> >
> > I would add that we should fill a ticket like "ST_Summary should report
> the x and y raster coordinates of the max and the min". So four new columns...
> >
> > Pierre
> >
> >> -----Original Message-----
> >> From: postgis-users-bounces at postgis.refractions.net
> <mailto:postgis-users-bounces at postgis.refractions.net> [mailto:postgis-users-
> >> bounces at postgis.refractions.net
> <mailto:bounces at postgis.refractions.net> ] On Behalf Of Bborie Park
> >> Sent: Monday, June 25, 2012 4:32 PM
> >> To: postgis-users at postgis.refractions.net <mailto:postgis-
> users at postgis.refractions.net>
> >> Subject: Re: [postgis-users] Finding highest cell value in raster using
> ST_Value
> >>
> >> Egge-Jan,
> >>
> >> That is an intriguing question with no clean/simple solution. The
> >> fastest approach may be to call ST_Reclass() to create a 1BB mask
> based
> >> upon that value and the pass the resulting raster to
> >> ST_PixelAsPolygons() which will give you what you want.
> >>
> >> Yes, the above is a round-about way to do this. This is something I'll
> >> (ST_PixelofValue?) see about adding for PostGIS 2.1.
> >>
> >> -bborie
> >>
> >> On 06/25/2012 01:16 PM, e.j.h.polle wrote:
> >>> Hi,
> >>>
> >>> OK - with ST_SummaryStats it is easy to retrieve the highest value in
> the
> >>> raster, but then I only have this value. Now I want to retrieve
> >>> (information about) the cell/pixel having this value, to be able to
> >>> visualize the highest point on the map. My original query (see first
> post)
> >>> does give me this information (after 45 seconds...).
> >>>
> >>> How would I go about to get hold of the pixel with the highest
> value,
> >>> knowing this value?
> >>>
> >>> Cheers,
> >>>
> >>> Egge-Jan
> >>>
> >>> On Sunday, June 24, 2012 8:47:58 PM UTC+1, DavidRA wrote:
> >>>>
> >>>> Why don't you use ST_SummaryStats instead ST_Value? That way
> you can get
> >>>> easily any basic stat, included the maximum value of the raster. It
> would
> >>>> be
> >>>> something like:
> >>>>
> >>>> SELECT (ST_SummaryStats(rast)).max FROM raster_table;
> >>>>
> >>>> --
> >>>> View this message in context:
> >>>> http://postgis.17.n6.nabble.com/Finding-highest-cell-value-in-
> raster-using- <http://postgis.17.n6.nabble.com/Finding-highest-cell-value-in-
> raster-using->
> >> ST-Value-tp4998545p4998554.html
> >>>> Sent from the PostGIS - User mailing list archive at Nabble.com.
> >>>> _______________________________________________
> >>>> postgis-users mailing list
> >>>> postgis-users at postgis.refractions.net <mailto:postgis-
> users at postgis.refractions.net>
> >>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
> <http://postgis.refractions.net/mailman/listinfo/postgis-users>
> >>>>
> >>>
> >>> On Sunday, June 24, 2012 8:47:58 PM UTC+1, DavidRA wrote:
> >>>>
> >>>> Why don't you use ST_SummaryStats instead ST_Value? That way
> you can get
> >>>> easily any basic stat, included the maximum value of the raster. It
> would
> >>>> be
> >>>> something like:
> >>>>
> >>>> SELECT (ST_SummaryStats(rast)).max FROM raster_table;
> >>>>
> >>>> --
> >>>> View this message in context:
> >>>> http://postgis.17.n6.nabble.com/Finding-highest-cell-value-in-
> raster-using- <http://postgis.17.n6.nabble.com/Finding-highest-cell-value-in-
> raster-using->
> >> ST-Value-tp4998545p4998554.html
> >>>> Sent from the PostGIS - User mailing list archive at Nabble.com.
> >>>> _______________________________________________
> >>>> postgis-users mailing list
> >>>> postgis-users at postgis.refractions.net <mailto:postgis-
> users at postgis.refractions.net>
> >>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
> <http://postgis.refractions.net/mailman/listinfo/postgis-users>
> >>>>
> >>>
> >>> On Sunday, June 24, 2012 8:47:58 PM UTC+1, DavidRA wrote:
> >>>>
> >>>> Why don't you use ST_SummaryStats instead ST_Value? That way
> you can get
> >>>> easily any basic stat, included the maximum value of the raster. It
> would
> >>>> be
> >>>> something like:
> >>>>
> >>>> SELECT (ST_SummaryStats(rast)).max FROM raster_table;
> >>>>
> >>>> --
> >>>> View this message in context:
> >>>> http://postgis.17.n6.nabble.com/Finding-highest-cell-value-in-
> raster-using- <http://postgis.17.n6.nabble.com/Finding-highest-cell-value-in-
> raster-using->
> >> ST-Value-tp4998545p4998554.html
> >>>> Sent from the PostGIS - User mailing list archive at Nabble.com.
> >>>> _______________________________________________
> >>>> postgis-users mailing list
> >>>> postgis-users at postgis.refractions.net <mailto:postgis-
> users at postgis.refractions.net>
> >>>> http://postgis.refractions.net/mailman/listinfo/postgis-users
> <http://postgis.refractions.net/mailman/listinfo/postgis-users>
> >>>>
> >>>
> >>>
> >>>
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> >>
> >> --
> >> Bborie Park
> >> Programmer
> >> Center for Vectorborne Diseases
> >> UC Davis
> >> 530-752-8380
> >> bkpark at ucdavis.edu
> >> _______________________________________________
> >> postgis-users mailing list
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> users at postgis.refractions.net>
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> >
>
> --
> Bborie Park
> Programmer
> Center for Vectorborne Diseases
> UC Davis
> 530-752-8380
> bkpark at ucdavis.edu
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