Information on the shape of the ground can be required in the air for two quite different reasons. First, for visual fixing of position, that is to say, for ‘map-reading’; and second, for ensuring terrain clearance when flying on instruments. Obviously the second is of far greater importance than the first, yet unfortunately it is the first that, for historical reasons, has received the greater attention from cartographers; this paper will try to redress the balance, and indicate where action is needed at the present time to satisfy the second requirement.