[postgis-users] getting raster values for point from st_value
Pierre Racine
Pierre.Racine at sbf.ulaval.ca
Wed May 14 08:52:29 PDT 2014
What is this -s 5070 that you put in your raster2pgsql command? Should not it be 4269 (NAD 83)?
> -----Original Message-----
> From: Jason Mathis [mailto:jmathis at redzonesoftware.com]
> Sent: Wednesday, May 14, 2014 11:47 AM
> To: Pierre Racine; PostGIS Users Discussion
> Subject: RE: [postgis-users] getting raster values for point from st_value
>
> 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!
> > >
> > >
> > >
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>
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