[postgis-users] Finding highest cell value in raster using ST_Value

[Bborie Park]

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-ST-Value-tp4998545p4998554.html 
>> Sent from the PostGIS - User mailing list archive at Nabble.com. 
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>>
> 
> 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-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 
>> 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-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 
>> 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