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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,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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