e 
              between the XY plane and the outward normal vector at 
              P. For a point P not on the reference spheroid, the 
              planetographic latitude is that of the closest point 
              to P on the spheroid. 
 
              Latitude is measured in radians.  On input, the 
              range of latitude is unrestricted.  
 
   alt        Altitude of point above the reference spheroid. 
              Units of `alt' must match those of `re'. 
 
   re         Equatorial radi