Re: problems with multiple grids in McIDAS files

On Thu, 18 Jun 2009, Don Murray wrote:

> John/Robb-
>
> I'm trying to track down an issue with the projections in the
> McIDAS Grid IOSP.  The Lambert Conformal grids seem to be
> okay, but the PolarStereoGraphic and Mercator projections in
> the same file are not correct in the IDV or ToolsUI GridViewer.
> So, it's either a bad definition or a problem with the CoordSysBuilder.
>
> I'm comparing the 49x35 PS grids in testdata/grid/mcidas/GRID5510 with

Don,

I can't open any of the mcidas files in that directory. Since I'm working 
on the new index, I thought maybe that was the problem but I can open the 
files in the grid/gempak directory ok. Also, the NAM_ALaska-95km opens ok 
too. I'll have to do more research to see if the problem is my code, but 
I've been working to make all the index codings backwards compatiable. One 
thought is that you have multiple projections in the same file, that could 
cause problems too. Do any of the files in the mcidas directory have just 
one projection?  Are the projections correct?

Robb...


> the NAM Alaska 95 km grid (e.g.:
>
> dods://motherlode.ucar.edu:8080/thredds/dodsC/model/NCEP/NAM/Alaska_95km/NAM_Alaska_95km_20090618_1200.grib1
>
> The projection varaibles seem to have the same parameters that are used in 
> GridHorizCoordSys, although the McIDAS projection has more info (La2,
> Lo2, Latin1, Latin2, etc), but that is not used in GridHorizCoordSys.makePS:
>
> GRID5510:
>
>     char PS_X:49_Y:35;
>       :grid_mapping_name = "polar_stereographic";
>       :longitude_of_projection_origin = -150.0; // double
>       :straight_vertical_longitude_from_pole = -150.0; // double
>       :scale_factor_at_projection_origin = 0.933; // double
>       :latitude_of_projection_origin = 90.0; // double
>       :earth_shape = "Spherical";
>       :GDS_param_Dx = 95250.0; // double
>       :GDS_param_Dy = 95250.0; // double
>       :GDS_param_GDSkey = "PS X:49 Y:35";
>       :GDS_param_La1 = 42.07661981300264; // double
>       :GDS_param_La2 = 63.970746163829524; // double
>       :GDS_param_Latin1 = 60.0; // double
>       :GDS_param_Latin2 = 60.0; // double
>       :GDS_param_Lo1 = -175.6410058243053; // double
>       :GDS_param_Lo2 = -93.69006752597979; // double
>       :GDS_param_LoV = -150.0; // double
>       :GDS_param_Nx = 49; // int
>       :GDS_param_Ny = 35; // int
>       :GDS_param_Proj = 2; // int
>       :GDS_param_ProjFlag = "PS";
>       :_CoordinateTransformType = "Projection";
>       :_CoordinateAxisTypes = "GeoX GeoY";
>
> Alaska 95 km:
>
>   String Polar_Stereographic_projection_Grid;
>     :grid_mapping_name = "polar_stereographic";
>     :longitude_of_projection_origin = -150.0; // double
>     :straight_vertical_longitude_from_pole = -150.0; // double
>     :scale_factor_at_projection_origin = 0.933; // double
>     :latitude_of_projection_origin = 90.0; // double
>     :earth_shape = "spherical";
>     :GRIB_param_Dx = 95250.0; // double
>     :GRIB_param_Dy = 95250.0; // double
>     :GRIB_param_GDSkey = 464455425; // int
>     :GRIB_param_La1 = 42.085; // double
>     :GRIB_param_Lo1 = -175.641; // double
>     :GRIB_param_LoV = -150.0; // double
>     :GRIB_param_NpProj = "true";
>     :GRIB_param_Nx = 49; // int
>     :GRIB_param_Ny = 35; // int
>     :GRIB_param_ProjFlag = 0; // int
>     :GRIB_param_ResCompFlag = 8; // int
>     :GRIB_param_Winds = "Relative";
>     :GRIB_param_grid_name = "Polar Stereographic projection Grid";
>     :GRIB_param_grid_radius_spherical_earth = 6367.47; // double
>     :GRIB_param_grid_shape = "spherical";
>     :GRIB_param_grid_shape_code = 0; // int
>     :GRIB_param_grid_type = 5; // int
>     :GRIB_param_grid_units = "m";
>     :_CoordinateTransformType = "Projection";
>     :_CoordinateAxisTypes = "GeoX GeoY";
>
> The big difference is that the McIDAS grid has groups.
>
> Don
> *************************************************************
> Don Murray                               UCAR Unidata Program
> address@hidden                        P.O. Box 3000
> (303) 497-8628                              Boulder, CO 80307
> http://www.unidata.ucar.edu/staff/donm
> *************************************************************

===============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
address@hidden             WWW: http://www.unidata.ucar.edu/
===============================================================================