Question

I am using the NetCDF 4 java library from unidata to read GRIB2 files and am now trying to find a way to get timezone offsets for a given latitude/longitude. I have a .flt file for the northern hemisphere that contains all of this information and I know how to read it, I just don’t know how to do the map projection properly. I am able to do the projection using
LambertConformal(originLat, originLon, stdParallel1, stdParallel2) but I do not know how to use the projected x,y values inside the grid.

The grid values are Nx=1073 and Ny=689 and the projected values I’m getting for lat=33.92, lon=-84.33 are x=995 y=1035. I know the projected values are right, but I don’t know how to read the grid with them.

Maybe someone can help me understand the following values, too.

 :grid_mapping_name = "lambert_conformal_conic";
 :standard_parallel = 25.0; // double
 :longitude_of_central_meridian = 265.0; // double
 :latitude_of_projection_origin = 25.0; // double
 :earth_shape = "Earth spherical with radius specified by producer";
 :spherical_earth_radius_meters = 6371200.0; // double
 :GRIB_param_Dx = 5079.4062; // double
 :GRIB_param_Dy = 5079.4062; // double
 :GRIB_param_GDSkey = 1158554943; // int
 :GRIB_param_La1 = 20.192; // double
 :GRIB_param_LaD = 25.0; // double
 :GRIB_param_Latin1 = 25.0; // double
 :GRIB_param_Latin2 = 25.0; // double
 :GRIB_param_Lo1 = 238.446; // double
 :GRIB_param_LoV = 265.0; // double
 :GRIB_param_NpProj = "true";
 :GRIB_param_Nx = 1073; // int
 :GRIB_param_Ny = 689; // int
 :GRIB_param_ProjFlag = 0; // int
 :GRIB_param_Quasi = "false";
 :GRIB_param_ResCompFlag = 0; // int
 :GRIB_param_SpLat = -90.0; // double
 :GRIB_param_SpLon = 0.0; // double
 :GRIB_param_Winds = "True";
 :GRIB_param_grid_name = "Lambert Conformal";
 :GRIB_param_grid_radius_spherical_earth = 6371200.0; // double
 :GRIB_param_grid_shape = "Earth spherical with radius specified by producer";
 :GRIB_param_grid_shape_code = 1; // int
 :GRIB_param_grid_type = 30; // int
 :GRIB_param_grid_units = "m";

Answer 1

Have you tried posting on the Unidata website? They would probably be better at answering this type of question. In the past I have gotten great responses from them.
-Fred