anchor.diff:        xpla = xcar
         ypla = ycar
         zsig = z_coordinate
  -      z_coordinate = abs(z_coordinate) / (3.086e+16)
  +      z_coordinate = abs(z_coordinate) / METERS_IN_PARSEC
         rpla2 = xpla * xpla + ypla * ypla
         rpla = sqrt(rpla2)
         r2 = rpla * rpla + z_coordinate * z_coordinate
  
positive.code:      &                   a2 = 17.43,
       &                   md3 = 3.3d+09, 
       &                   a3 = 34.86,
       &                   g = 4.30026e-6
  
        real :: xcar, 
       &        ycar, 
  
negative.code:           ycar = ypla(wd_index)
  C         TODO: find out the meaning of wo and 8.0
            wo = ww(wd_index) + 8.0
            zo = real(coordinate_Zcylindr(wd_index) * METERS_IN_PARSEC)
  C         TODO: find out the meaning of ecini
            ecini = 0.5 * wo * wo
            call epot(zo, epoti)
  