Got the guts of this one from AvonLady, but there was a step missing:
1) In ‘Video Options' set terrain detail to ‘Very Low'
2) Call up any island in the editor
3) Place a player on the map so you can preview it
4) Press LEFT SHIFT and ‘-‘ on the num keypad at the same time
5) Type: topography
6) Press ‘M' to call up the map view
7) Listen to the hard drive thrash
Look in your root drive C:\ and there will be an emf file of the island
To give you an idea, Malden comes out at about 20Mb, Tonal at 50Mb.
Happy planning.