James,
Could do file a ticked and upload a sample file on http://trac.osgeo.org/gdal/ ?
Regards,
Ivan
James Hiebert wrote:
> Hi All,
>
> I'm trying to use GDAL (version 1.7.2 on Gentoo built with hdf5 and netcdf
> support) to read NetCDF files, but I'm a little unclear on how the NetCDF
> driver attempts to determine the georeferencing.
>
> The driver page here:
> http://www.gdal.org/frmt_netcdf.html
> states that it will attempt to read the metadata "spatial_ref" for a Well
> Know Text definition of the spatial reference (I assume that it means that
> it will try to use a global attribute of the NetCDF file named spatial_ref).
>
> Since this would be convenient for my application, I attempted to use GDAL
> this way without success.
>
> + I added a global attribute named "spatial_ref" with the WKT definition of
> the spatial reference system.
> + gdalinfo on the file still reports "Coordinate System is `'"
> + opening the file with the python bindings and calling dst.GetProjection()
> returns a blank string (i.e. no projection information)
>
> The full listings of my spatial reference definition, the output of ncdump
> and gdalinfo and the output from the python session are listed below. Can
> anyone tell me whether I'm doing something wrong, or should I not count on
> georeferencing being supported by the NetCDF driver?
>
> ~James
>
> james at basalt ~ $ ncatted -a spatial_ref,global,a,c,'PROJCS["unnamed",GEOGCS["Normal Sphere
> (r=6370997)",DATUM["unknown",SPHEROID["sphere",6370997,0]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]],PROJECTION["Polar_Stereographic"],PARAMETER["latitude_of_origin",60],PARAMETER["central_meridian",263],PARAMETER["scale_factor",1],PARAMETER["false_easting",3925000],PARAMETER["false_northing",8325000]]'
> narccap_ecpc-20c3m-tasmin-ncep.nc narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc
>
>
> james at basalt ~ $ ncdump -h narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc
> netcdf narccap_ecpc-20c3m-tasmin-ncep-with-srs {
> dimensions:
> xc = 123 ;
> yc = 104 ;
> time = UNLIMITED ; // (9496 currently)
> bnds = 2 ;
> variables:
> char polar_stereographic ;
> polar_stereographic:grid_mapping_name =
> "polar_stereographic" ;
> polar_stereographic:longitude_of_central_meridian = 263. ;
> polar_stereographic:straight_vertical_longitude_from_pole =
> 263. ;
> polar_stereographic:standard_parallel = 60. ;
> polar_stereographic:TrueGridLength_Latitude = 60. ;
> polar_stereographic:XGridLength_M = 50000. ;
> polar_stereographic:YGridLength_M = 50000. ;
> polar_stereographic:PoleOnPlane = "north" ;
> polar_stereographic:false_easting = 3925000. ;
> polar_stereographic:false_northing = 8325000. ;
> polar_stereographic:latitude_of_projection_origin = 90. ;
> double yc(yc) ;
> yc:long_name = "y-coordinate of Cartesian system" ;
> yc:standard_name = "projection_y_coordinate" ;
> yc:axis = "Y" ;
> yc:units = "m" ;
> double xc(xc) ;
> xc:long_name = "x-coordinate of Cartesian system" ;
> xc:standard_name = "projection_x_coordinate" ;
> xc:axis = "X" ;
> xc:units = "m" ;
> double lon(yc, xc) ;
> lon:units = "degrees_east" ;
> lon:long_name = "longitude" ;
> lon:standard_name = "longitude" ;
> lon:axis = "X" ;
> lon:NX_NumPntsOnParallel = 123 ;
> lon:NY_NumPntsOnMeridian = 104 ;
> lon:actual_range = 211.5412f, 316.2759f ;
> lon:XGridLength_M = 50000. ;
> lon:YGridLength_M = 50000. ;
> lon:PoleOnPlane = "north" ;
> double lat(yc, xc) ;
> lat:units = "degrees_north" ;
> lat:long_name = "latitude" ;
> lat:standard_name = "latitude" ;
> lat:axis = "Y" ;
> lat:NX_NumPntsOnParallel = 123 ;
> lat:NY_NumPntsOnMeridian = 104 ;
> lat:actual_range = 21.23807f, 67.63758f ;
> lat:XGridLength_M = 50000. ;
> lat:YGridLength_M = 50000. ;
> lat:PoleOnPlane = "north" ;
> ...
>
> // global attributes:
> ...
> :history = "Mon Aug 9 13:44:50 2010: ncatted -a
> spatial_ref,global,a,c,PROJCS[\"unnamed\",GEOGCS[\"Normal
> Sphere
> (r=6370997)\",DATUM[\"unknown\",SPHEROID[\"sphere\",6370997,0]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433]],PROJECTION[\"Polar_Stereographic\"],PARAMETER[\"latitude_of_origin\",60],PARAMETER[\"central_meridian\",263],PARAMETER[\"scale_factor\",1],PARAMETER[\"false_easting\",3925000],PARAMETER[\"false_northing\",8325000]]
> narccap_ecpc-20c3m-tasmin-ncep.nc
> narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc\n",
> "Fri May 8 09:34:14 2009: ncrcat
> tasmin_ECPC_1979010106.nc tasmin_ECPC_1981010106.nc
> tasmin_ECPC_1986010106.nc tasmin_ECPC_1991010106.nc
> tasmin_ECPC_1996010106.nc tasmin_ECPC_2001010106.nc
> narccap_ecpc-20c3m-tasmin-ncep.nc" ;
> :nco_openmp_thread_number = 1 ;
> :spatial_ref = "PROJCS[\"unnamed\",GEOGCS[\"Normal Sphere
> (r=6370997)\",DATUM[\"unknown\",SPHEROID[\"sphere\",6370997,0]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433]],PROJECTION[\"Polar_Stereographic\"],PARAMETER[\"latitude_of_origin\",60],PARAMETER[\"central_meridian\",263],PARAMETER[\"scale_factor\",1],PARAMETER[\"false_easting\",3925000],PARAMETER[\"false_northing\",8325000]]"
> ;
> }
>
> james at basalt ~ $ gdalinfo narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc
> Driver: netCDF/Network Common Data Format
> Files: narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc
> narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc.aux.xml
> Size is 512, 512
> Coordinate System is `'
> Metadata:
> ...
> NC_GLOBAL#history1=Original output in GRIB 1
> NC_GLOBAL#history2=Contains modifications made to original data
> NC_GLOBAL#history=Mon Aug 9 13:44:50 2010: ncatted -a
> spatial_ref,global,a,c,PROJCS["unnamed",GEOGCS["Normal Sphere
> (r=6370997)",DATUM["unknown",SPHEROID["sphere",6370997,0]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]],PROJECTION["Polar_Stereographic"],PARAMETER["latitude_of_origin",60],PARAMETER["central_meridian",263],PARAMETER["scale_factor",1],PARAMETER["false_easting",3925000],PARAMETER["false_northing",8325000]]
> narccap_ecpc-20c3m-tasmin-ncep.nc
> narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc
> Fri May 8 09:34:14 2009: ncrcat tasmin_ECPC_1979010106.nc
> tasmin_ECPC_1981010106.nc tasmin_ECPC_1986010106.nc
> tasmin_ECPC_1991010106.nc tasmin_ECPC_1996010106.nc
> tasmin_ECPC_2001010106.nc narccap_ecpc-20c3m-tasmin-ncep.nc
> NC_GLOBAL#nco_openmp_thread_number=1
> NC_GLOBAL#spatial_ref=PROJCS["unnamed",GEOGCS["Normal Sphere
> (r=6370997)",DATUM["unknown",SPHEROID["sphere",6370997,0]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]],PROJECTION["Polar_Stereographic"],PARAMETER["latitude_of_origin",60],PARAMETER["central_meridian",263],PARAMETER["scale_factor",1],PARAMETER["false_easting",3925000],PARAMETER["false_northing",8325000]]
> Subdatasets:
> SUBDATASET_1_NAME=NETCDF:"narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc":lon
> SUBDATASET_1_DESC=[104x123] longitude (64-bit floating-point)
> SUBDATASET_2_NAME=NETCDF:"narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc":lat
> SUBDATASET_2_DESC=[104x123] latitude (64-bit floating-point)
> SUBDATASET_3_NAME=NETCDF:"narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc":time_bnds
> SUBDATASET_3_DESC=[9496x2] time_bnds (64-bit floating-point)
> SUBDATASET_4_NAME=NETCDF:"narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc":tasmin
> SUBDATASET_4_DESC=[9496x104x123] air_temperature (32-bit floating-point)
> Corner Coordinates:
> Upper Left ( 0.0, 0.0)
> Lower Left ( 0.0, 512.0)
> Upper Right ( 512.0, 0.0)
> Lower Right ( 512.0, 512.0)
> Center ( 256.0, 256.0)
>
>
> james at basalt ~ $ python
>>>> from osgeo import gdal
>>>> dst = gdal.Open("narccap_ecpc-20c3m-tasmin-ncep-with-srs.nc")
>>>> dst.GetProjection()
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>