MI Portrait or landscape ?

[Scott England]

I have a map window containing a country with part of it shaded thematically.  I have written code that will zoom in to the closest view on just that section, but I need to determine programatically which orientation would be the best for the map i.e. is the shaded area taller than it is wide or vice versa ??  When I know which it is then I can change the shape of the map window to portrait/landscape and then zoom in.  Which is the best way to do this ??   TIA,   Scott..