function dasp(lat)
% DASP sets data aspect ratio to 1
% or if optional lat is supplied, crude projection
if(nargin==1),
   xfac=cos(lat*pi/180);
   set (gca, 'DataAspectRatio', [1 xfac 1] );
else
   set (gca, 'DataAspectRatio', [1 1 1] );
end
