pro test_const_alt
  a_w=get_wgs84_const(/re)
  b_w=get_wgs84_const(/rp)
  h_c=83d

  help,a_w,b_w
  
  a_c=a_w+h_c
  b_c=b_w+h_c

  help,a_c,b_c

  x_c=dindgen(a_c)
  z_c=b_c*sqrt(1-x_c^2/a_c^2)

  x_w=dindgen(a_w)
  z_w=b_w*sqrt(1-x_w^2/a_w^2)

  print,z_c[0]-b_w
  print,b_w-a_w
  print,b_c-a_c


  y_c=x_c*0

;  plot,x_c,y_c
;  oplot,x_w,y_w

  xyz_c=compose_grid(x_c,y_c,z_c)
  help,xyz_c

  lla_c=xyz_to_lla(xyz_c)
  help,lla_c

  xyz2_c=lla_to_xyz(lla_c)

  mn=min(abs(xyz2_c-xyz_c),max=mx)
  help,mn,mx

  resolve_grid,lla_c,x=lat_c,y=lon_c,z=alt_c

  plot,x_c,alt_c,/ynoz

  print,alt_c[0]

end