Is there any reason why the radius tag is: "spherical_earth_radius_meters"
instead of the CF-1.0 tag:
"earth_radius"
?
kss
# ===================
Kyle Shannon
Physical Science Technician
RMRS Fire Sciences Lab
Fire, Fuels & Smoke - RWU 4405
5775 Highway 10 W.
Missoula, MT 59808
(406) 829-6954
kshannon@xxxxxxxxx
# ===================
On Mon, Feb 15, 2010 at 9:52 AM, John Caron <caron@xxxxxxxxxxxxxxxx> wrote:
> Robb Kambic wrote:
>
>> On Tue, 9 Feb 2010, Kyle Shannon wrote:
>>
>> Hello all,
>>> I am using the netCDF subsetting service on ucar's motherlode thredds
>>> server. I am having an issue with the projection of the subset.
>>>
>>> I run ncdump on the entire ndfd grid (full spatial extents) and get:
>>>
>>> kyle@Lucky13:~/nc_issue$ ncdump -h ndfd_all.nc | grep Lambert_Conformal
>>> Maximum_temperature:grid_mapping = "Lambert_Conformal" ;
>>> char Lambert_Conformal ;
>>> Lambert_Conformal:grid_mapping_name = "lambert_conformal_conic" ;
>>> Lambert_Conformal:standard_parallel = 25. ;
>>> Lambert_Conformal:longitude_of_central_meridian = 265. ;
>>> Lambert_Conformal:latitude_of_projection_origin = 25. ;
>>> Lambert_Conformal:earth_shape = "Earth spherical with radius
>>> specified by producer in m" ;
>>> Lambert_Conformal:spherical_earth_radius_meters = 6371200. ;
>>> Lambert_Conformal:GRIB_param_Dx = 5079.361 ;
>>> Lambert_Conformal:GRIB_param_Dy = 5079.472 ;
>>> Lambert_Conformal:GRIB_param_GDSkey = 801839731 ;
>>> *Lambert_Conformal:GRIB_param_La1 = 20.192 ;
>>> Lambert_Conformal:GRIB_param_LaD = 25. ;
>>> Lambert_Conformal:GRIB_param_Latin1 = 25. ;
>>> Lambert_Conformal:GRIB_param_Latin2 = 25. ;
>>> *Lambert_Conformal:GRIB_param_Lo1 = 238.446 ;
>>> Lambert_Conformal:GRIB_param_LoV = 265. ;
>>> Lambert_Conformal:GRIB_param_NpProj = "true" ;
>>> Lambert_Conformal:GRIB_param_Nx = 1073 ;
>>> Lambert_Conformal:GRIB_param_Ny = 689 ;
>>> Lambert_Conformal:GRIB_param_ProjFlag = 0 ;
>>> Lambert_Conformal:GRIB_param_Quasi = "false" ;
>>> Lambert_Conformal:GRIB_param_ResCompFlag = 8 ;
>>> Lambert_Conformal:GRIB_param_SpLat = -90. ;
>>> Lambert_Conformal:GRIB_param_SpLon = 0. ;
>>> Lambert_Conformal:GRIB_param_VectorComponentFlag = "gridRelative"
>>> ;
>>> Lambert_Conformal:GRIB_param_Winds = "Relative" ;
>>> Lambert_Conformal:GRIB_param_grid_name = "Lambert_Conformal" ;
>>> Lambert_Conformal:GRIB_param_grid_radius_spherical_earth =
>>> 6371200.
>>> ;
>>> Lambert_Conformal:GRIB_param_grid_shape = "Earth spherical with
>>> radius specified by producer in m" ;
>>> Lambert_Conformal:GRIB_param_grid_shape_code = 1 ;
>>> Lambert_Conformal:GRIB_param_grid_type = 30 ;
>>> Lambert_Conformal:GRIB_param_grid_units = "m" ;
>>> Lambert_Conformal:GRIB_param_scanning_mode = 64 ;
>>> Lambert_Conformal:_CoordinateTransformType = "Projection" ;
>>> Lambert_Conformal:_CoordinateAxisTypes = "GeoX GeoY" ;
>>>
>>> and when I run it on the subsetted data, I get:
>>>
>>> kyle@Lucky13:~/nc_issue$ ncdump -h ndfd.nc | grep Lambert_Conformal
>>> Maximum_temperature:grid_mapping = "Lambert_Conformal" ;
>>> char Lambert_Conformal ;
>>> Lambert_Conformal:grid_mapping_name = "lambert_conformal_conic" ;
>>> Lambert_Conformal:standard_parallel = 25. ;
>>> Lambert_Conformal:longitude_of_central_meridian = 265. ;
>>> Lambert_Conformal:latitude_of_projection_origin = 25. ;
>>> Lambert_Conformal:earth_shape = "Earth spherical with radius
>>> specified by producer in m" ;
>>> Lambert_Conformal:spherical_earth_radius_meters = 6371200. ;
>>> Lambert_Conformal:GRIB_param_Dx = 5079.361 ;
>>> Lambert_Conformal:GRIB_param_Dy = 5079.472 ;
>>> Lambert_Conformal:GRIB_param_GDSkey = 801839731 ;
>>> Lambert_Conformal:GRIB_param_La1 = 20.192 ;
>>> Lambert_Conformal:GRIB_param_LaD = 25. ;
>>> Lambert_Conformal:GRIB_param_Latin1 = 25. ;
>>> Lambert_Conformal:GRIB_param_Latin2 = 25. ;
>>> Lambert_Conformal:GRIB_param_Lo1 = 238.446 ;
>>> Lambert_Conformal:GRIB_param_LoV = 265. ;
>>> Lambert_Conformal:GRIB_param_NpProj = "true" ;
>>> Lambert_Conformal:GRIB_param_Nx = 1073 ;
>>> Lambert_Conformal:GRIB_param_Ny = 689 ;
>>> Lambert_Conformal:GRIB_param_ProjFlag = 0 ;
>>> Lambert_Conformal:GRIB_param_Quasi = "false" ;
>>> Lambert_Conformal:GRIB_param_ResCompFlag = 8 ;
>>> Lambert_Conformal:GRIB_param_SpLat = -90. ;
>>> Lambert_Conformal:GRIB_param_SpLon = 0. ;
>>> Lambert_Conformal:GRIB_param_VectorComponentFlag = "gridRelative"
>>> ;
>>> Lambert_Conformal:GRIB_param_Winds = "Relative" ;
>>> Lambert_Conformal:GRIB_param_grid_name = "Lambert_Conformal" ;
>>> Lambert_Conformal:GRIB_param_grid_radius_spherical_earth =
>>> 6371200.
>>> ;
>>> Lambert_Conformal:GRIB_param_grid_shape = "Earth spherical with
>>> radius specified by producer in m" ;
>>> Lambert_Conformal:GRIB_param_grid_shape_code = 1 ;
>>> Lambert_Conformal:GRIB_param_grid_type = 30 ;
>>> Lambert_Conformal:GRIB_param_grid_units = "m" ;
>>> Lambert_Conformal:GRIB_param_scanning_mode = 64 ;
>>> Lambert_Conformal:_CoordinateTransformType = "Projection" ;
>>> Lambert_Conformal:_CoordinateAxisTypes = "GeoX GeoY" ;
>>> Total_cloud_cover:grid_mapping = "Lambert_Conformal" ;
>>> Wind_direction_from_which_blowing:grid_mapping =
>>> "Lambert_Conformal"
>>> ;
>>> Wind_speed:grid_mapping = "Lambert_Conformal" ;
>>>
>>> My question is, how can the latitude and longitude of the 1st cell not
>>> change after the subsetting? It appears that the meta data from the full
>>> dataset is just copied to the subset data. Is this correct?
>>>
>>
>> Kyle,
>>
>
> As Robb says, all the Lambert_Conformal:GRIB_XXXX attributes are simply
> copied over to the netcdf file from the GRIB GDS. We dont use these GRIB
> parameters for anything. Robb failed to mention that the actual coordinates
> are stored in the x and y coordinate variables in the netcdf file. In this
> case these are projection coordinates, which are converted to lat/lon values
> through the lambert conformal projection. If you check the "include
> lat/lon" box, the 2D lat/lon coordinates will also be included in the file,
> as Robb indicates. This is needed to be in strict compliance with CF
> conventions, but is not needed by the CDM software.
>
>
>
>> Yes. The GDS parameters that you are looking at are the parameters for the
>> model, so they are copied over to the resulting file. Usually users make the
>> subsetting file name contain the latitude and longitude information of the
>> subset.
>>
>> How can I
>>
>>> figure out where my subset data is on the world?
>>>
>>>
>> Click the check box on the sub-set page for "Add Lat/Lon to file"
>> to the resulting file. Now the ncdump on the Lat and Lon variables will be
>> available.
>>
>> When you open/display the file the information will also be available.
>>
>> On a programming level:
>>
>> If you open the file as a GridDataset, you should be able to access the
>> needed information. Here's an url about GridDatasets:
>>
>>
>> http://www.unidata.ucar.edu/software/netcdf-java/tutorial/GridDatatype.html
>>
>> You will also need to to look at the java-docs on the GridDataset.
>>
>>
>> RObb...
>>
>>
>> Thanks, sorry for the messy message.
>>>
>>> kss
>>> # ===================
>>> Kyle Shannon
>>> Physical Science Technician
>>> RMRS Fire Sciences Lab
>>> Fire, Fuels & Smoke - RWU 4405
>>> 5775 Highway 10 W.
>>> Missoula, MT 59808
>>> (406) 829-6954
>>> kshannon@xxxxxxxxx
>>> # ===================
>>>
>>>
>>>
>> ===============================================================================
>>
>> Robb Kambic Unidata Program Center
>> Software Engineer III Univ. Corp for Atmospheric Research
>> rkambic@xxxxxxxxxxxxxxxx WWW: http://www.unidata.ucar.edu/
>>
>> ===============================================================================
>>
>>
>> ------------------------------------------------------------------------
>>
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>
>
