[postgis-users] getting raster values for point from st_value

Wed May 14 08:46:53 PDT 2014

Well I was visualizing the tiff file not the postgis raster table. Its seems somewhere along the lines the qgis raster plugin dropped off. Although I am able to see the raster tables in the db manager and can drag/drop the table, horribly slow but works. 

The raster extents or just the raster table do not overlay with the point, which explains the problem. I still don’t understand what I did wrong. Attaching a screen shot. 

thanks, 

On May 14, 2014 at 7:01:27 AM, Pierre Racine (pierre.racine at sbf.ulaval.ca) wrote:

You said you could visualize this table in QGIS? Or were you speaking about a shapefile? You can visualize the rastextets table and the points table the same way.  

Pierre  

> -----Original Message-----  
> From: Jason Mathis [mailto:jmathis at redzonesoftware.com]  
> Sent: Tuesday, May 13, 2014 6:30 PM  
> To: PostGIS Users Discussion; Pierre Racine  
> Subject: Re: [postgis-users] getting raster values for point from st_value  
>  
> Hi Pierre,  
>  
> Thanks so much for super quick response. You will have to forgive me I am  
> fairly new to postgis.  
>  
> Creating the table is no problem but how would I check if it overlaps with  
> my points?  
>  
> thanks!  
>  
>  
>  
> On May 13, 2014 at 4:08:40 PM, Pierre Racine (pierre.racine at sbf.ulaval.ca)  
> wrote:  
>  
>  
> Create a new table with the extents of the raster tiles and check if it  
> overlaps with your points:  
>  
> CREATE TABLE rastextets AS  
> SELECT rast::geometry  
> FROM tbl_raster  
>  
> Pierre  
>  
> > -----Original Message-----  
> > From: postgis-users-bounces at lists.osgeo.org [mailto:postgis-  
> users-  
> > bounces at lists.osgeo.org] On Behalf Of Jason Mathis  
> > Sent: Tuesday, May 13, 2014 5:56 PM  
> > To: postgis-users at lists.osgeo.org  
> > Subject: [postgis-users] getting raster values for point from  
> st_value  
> >  
> > Hi all,  
> >  
> > I have recently loaded a good amount of rasterized shape files into  
> a db. I  
> > mainly used gdal_rasterize and raster2pgsql. The shape files were  
> in NAD83  
> > so I used the below commands to rasterized and load.  
> >  
> > gdal_rasterize -at -a desc -where "desc='Very High'" -burn 2 -tr 30  
> 30 -ot  
> > byte -a_nodata -99 shape_file.shp raster.tiff  
> > raster2pgsql -d -s 5070 -t 100x100 -F -I -C -Y raster.tiff tbl_raster |  
> psql -d  
> > raster_db  
> >  
> > I had two sets of shape files one set had about 10 burn values and  
> another  
> > had about 50. The issue is getting these values out of the raster. I  
> believe I  
> > should be using something from this page:  
> > http://postgis.net/docs/RT_ST_Value.html.  
> >  
> > I can visualize this file in QGIS and it looks good, the histogram  
> shows  
> > values. I can also use the postgis functions, st_summarystats or  
> > st_histogram to see some data but I need to be able to query a  
> given point  
> > and return the raster value.  
> >  
> > I have this:  
> >  
> > SELECT ST_Value(rast,(ST_Point( -111.750185, 34.886948)))  
> > FROM tbl_raster  
> > WHERE st_intersects(rast, (ST_Point(-111.750185, 34.886948)))  
> >  
> > Then i thought oh wait should I set the srid?:  
> >  
> > SELECT ST_Value(rast,(ST_SetSRID(ST_Point( -111.750185,  
> > 34.886948),5070)))  
> > FROM tbl_raster  
> > WHERE st_intersects(rast, (ST_SetSRID(ST_Point(-111.750185,  
> > 34.886948),5070)))  
> >  
> > Still I get nothing, then I thought I need to transform so I got this:  
> >  
> > SELECT ST_Value(rast,(ST_Transform(ST_SetSRID(ST_Point( -  
> 111.762866,  
> > 34.874309),5070),4326)))  
> > FROM tbl_raster  
> > WHERE st_intersects(rast, (ST_Transform(ST_SetSRID(ST_Point( -  
> > 111.762866, 34.874309),5070),4326)))  
> >  
> > But in the end nothing.  
> >  
> > I did need to add the SRID to the spatial_ref_sys table:  
> >  
> > INSERT into spatial_ref_sys (srid, auth_name, auth_srid,  
> proj4text, srtext)  
> > values ( 5070, 'EPSG', 5070, '+proj=aea +lat_1=29.5 +lat_2=45.5  
> +lat_0=23  
> > +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80  
> +towgs84=0,0,0,0,0,0,0  
> > +units=m +no_defs ', 'PROJCS["NAD83 / Conus  
> >  
> Albers",GEOGCS["NAD83",DATUM["North_American_Datum_1983",SPHER  
> > OID["GRS  
> >  
> 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0,  
> >  
> 0,0,0,0,0,0],AUTHORITY["EPSG","6269"]],PRIMEM["Greenwich",0,AUTHORIT  
> >  
> Y["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG  
> >  
> ","9122"]],AUTHORITY["EPSG","4269"]],PROJECTION["Albers_Conic_Equal_  
> >  
> Area"],PARAMETER["standard_parallel_1",29.5],PARAMETER["standard_par  
> >  
> allel_2",45.5],PARAMETER["latitude_of_center",23],PARAMETER["longitude  
> > _of_center",-  
> >  
> 96],PARAMETER["false_easting",0],PARAMETER["false_northing",0],UNIT["  
> >  
> metre",1,AUTHORITY["EPSG","9001"]],AXIS["X",EAST],AXIS["Y",NORTH],AUT  
> > HORITY["EPSG","5070"]]’);  
> >  
> > But ultimately I have nothing I can’t seem to get any data out  
> using a query  
> > with a point value. I am thinking it has to do with the srid? Since I  
> can  
> > visually inspect it and see data.  
> >  
> > Anyone have any hot ideas as to why I am not seeing data?  
> >  
> > Thanks!  
> >  
> >  
> >  
> > This transmission contains confidential and privileged information  
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>  
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