The first argument, xnum , specifies the number of grid points in the X direction. Negative values indicate western longitudes. It may continue into the next record in the descriptor file, but note that records may not have more than 255 characters. This entry defines the grid point values for the Y dimension. The first argument, ynum , specifies the number of grid points in the Y direction.
Negative values indicate southern latitides.
It is assumed that the Y dimension values go from south to north, so increment is always positive. It may continue into the next record in the descriptor file, but note that records may not have more than 255 characters. This argument indicates the first gaussian grid number. If the data span all latitudes, start would be 1, indicating the southernmost gaussian grid latitude. This entry defines the grid point values for the Z dimension.