 [1,n] = size(lon); double = class(lon)

             This is the angle between the prime meridian and the meridian
             containing 'rectan'.  For bodies having prograde (aka
             direct) rotation, the direction of increasing
             longitude is positive west:  from the +X axis of the
             rectangular coordinate system toward the -Y axis.
             For bodies having retrograde rotation, the direction
             of increasing longitude is positive east:  from the +X
       