Grid/region problem

["Donald S. Dunbar" <dsd@xxxxxxx>]

I have data on a 100x100 grid that is rectangular only when drawn on a polar
stereographic projection.  I know the (lon,lat) coordinates of each vertex.
Presently, I use ferret as follows:

define axis/x=1:100:1 ax
define axis/y=1:100:1 ay
define grid/x=ax/y=ay g
file/grid=g/var=h,lon,lat data_file
shade h,lon,lat

I use (lon,lat)=(-4,62), for example, in "data_file" for (4W,62N).  This
does what I want, sort of.  What I really want to do, though, is something
like:

define region/x=5w:16e/y=62n:69n reg
set region reg
shade h,lon,lat

That is, I want to be able to control the region that I'm plotting, and
maybe apply a map projection.

This doesn't work though, apparently because the underlying axes of h don't
overlap the region.  But why doesn't ferret use the (lon,lat) information
provided in the shade command to override these?  Aren't I telling ferret to
ignore the axes and plot data at the locations given by (lon,lat)?

How can I specify axes for h in some other way so that this works?  More to
the point, what is the best way to handle this type of gridded data?

I've used ferret for a long time and I feel I'm missing something basic
here.