Re: [netcdf-java] Problem with Polar Stereographic GRIB2

• To: Matt Foster <Matthew.Foster@xxxxxxxx>
• Subject: Re: [netcdf-java] Problem with Polar Stereographic GRIB2
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Tue, 28 Sep 2010 16:04:00 -0600

 Hi Matt:

ill let you know when a release with this fix in it is ready.

thanks!

John

On 9/28/2010 5:48 AM, Matt Foster wrote:

John,

Attached is some output from wgrib2. The first 4 commands are showing what wgrib2 thinks the lat/lon is for the 4 corners of the grid. The final command shows the projection information it has determined.

Let me know if there's other information you need.

Matt


John Caron wrote:

its unusual to use Polar_Stereographic for texas!

anyway, do you know what the correct range should be? what does wgrib2 say? Send as much info as possible.

heres what we are reading:

 char Polar_Stereographic;
     :grid_mapping_name = "polar_stereographic";
     :longitude_of_projection_origin = 259.28094482421875; // double

:straight_vertical_longitude_from_pole = 259.28094482421875; // double

     :scale_factor_at_projection_origin = 0.933; // double
     :latitude_of_projection_origin = 90.0; // double

:earth_shape = "Earth spherical with radius specified by producer in m";

     :earth_radius = 6371.2001953125; // double
     :GRIB_param_Dx = 5000.0; // double
     :GRIB_param_Dy = 5000.0; // double
     :GRIB_param_GDSkey = -2046278676; // int
     :GRIB_param_La1 = 26.023346; // double
     :GRIB_param_LaD = 34.18336; // double
     :GRIB_param_Lo1 = 251.02313; // double
     :GRIB_param_LoV = 259.28094; // double
     :GRIB_param_NpProj = "true";
     :GRIB_param_Nx = 358; // int
     :GRIB_param_Ny = 353; // int
     :GRIB_param_ProjFlag = 0; // int
     :GRIB_param_Quasi = "false";
     :GRIB_param_ResCompFlag = 8; // int
     :GRIB_param_VectorComponentFlag = "gridRelative";
     :GRIB_param_Winds = "Relative";
     :GRIB_param_grid_name = "Polar_Stereographic";
     :GRIB_param_grid_radius_spherical_earth = 6371.2; // double

:GRIB_param_grid_shape = "Earth spherical with radius specified by producer in m";

     :GRIB_param_grid_shape_code = 1; // int
     :GRIB_param_grid_type = 20; // int
     :GRIB_param_grid_units = "m";
     :GRIB_param_scanning_mode = 80; // int
     :_CoordinateTransformType = "Projection";
     :_CoordinateAxisTypes = "GeoX GeoY";


  Polar_Stereographic type=Projection
    grid_mapping_name = stereographic
    longitude_of_projection_origin = 259.28094482421875
    latitude_of_projection_origin = 90.0
    scale_factor_at_projection_origin = 0.933
    impl.class= ucar.unidata.geoloc.projection.Stereographic



On 9/24/2010 8:50 AM, Matt Foster wrote:

John,

Here ya go...it's output from LAPS.

Matt


John Caron wrote:

On 9/24/2010 8:15 AM, Matt Foster wrote:

I'm not sure where the problem lies with what I'm seeing, so I thought I'd start here...

I'm having a problem reading a Polar Stereographic GRIB2 file with NetCDF-Java. I actually first encountered the problem when trying to view this data in IDV, and replicated it with some simple test code using NetCDF-Java 4.1. The problem is that the lower-left corner of the data is projected correctly, but not the upper-right. The upper-right corner is to the southwest of where it should be. Using the wgrib2 utility yields the correct points, so I believe the grib file itself is OK.

Are there any known issues with Polar Stereographic GRIB2 that could explain this?

If not, what additional information can I provide to try and figure out the problem?

Matt


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Hi Matt:

Can you send a sample file with the problem?

John

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a trail.
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• References:
  • [netcdf-java] Problem with Polar Stereographic GRIB2
    • From: Matt Foster