Final 200 feet under autoland
An autoland can be performed when a CAT II or III ILS (Instrument Landing System) approach is available (bad things can happen otherwise: Why don&#39;t pilots always use autoland?). The decision height for these approaches is lower than the usual 200 ft:


Cat I: DA 200 ft or higher
Cat II: DA 100-200 ft
Cat III A: DA &lt; 100 ft
Cat III B: DA &lt; 50 ft


The pilots must have the runway (or runway lighting) in sight when reaching the decision height. Otherwise, a go around must be executed. But this does not mean that the ILS signal is no longer available. The autoland system continues to use the ILS signal together with the RA (radio altimeter) to fly the aircraft. That means the autopilot uses the localizer deviation to control the aircraft laterally (during the approach, the flare and even after landing) and the glide slope deviation vertically until the RA indicates it is time to start the flare (at this time glide slope is ignored).

The exact details will of course depend on the aircraft model. Here is how the autoland works on a Boeing 737 NG (source: FCOM v2 4.20.19 Automatic Flight - System Description):


  500 Feet Radio Altitude
  
  The pilot is required to check for the presence of LAND 3 or LAND 2 in order to
  continue the autoland.
  If the second autopilot in CMD remains armed and does not engage, LAND 2 or
  LAND 3 does not annunciate. Instead, the amber NO AUTOLAND annunciation
  alerts the pilot that dual control has not been established and the autoland is to be
  discontinued.
  
  450 Feet Radio Altitude
  
  The alignment mode is enabled which provides rudder compensation for the
  purpose of decreasing large crab angles produced by crosswinds, and to control
  the adverse moments caused by an engine failure. The automatic correction for
  aircraft crab angle due to crosswinds and engine failure enhances flight crew
  runway perspective and provides optimal aircraft position for initiation of rollout
  control. In a strong crosswind, the airplane does not fully align with the runway
  but lands in a slight crab. Sideslip is limited to 5 degrees. This mode is not
  annunciated.
  
  400 Feet Radio Altitude
  
  The stabilizer is automatically trimmed an additional amount nose up. If the A/Ps
  subsequently disengage, forward control column force may be required to hold the
  desired pitch attitude.
  
  If FLARE is not armed by approximately 350 feet RA, both A/Ps automatically
  disengage.
  
  Flare
  
  The A/P flare maneuver starts at approximately 50 feet RA and is completed at
  touchdown:
  
  
  FLARE engaged is annunciated and F/D command bars retract.
  FLARE engaged is annunciated and with LAND 3 annunciated, F/D
  command bars center.
  the A/T begins retarding thrust at approximately 27 feet RA so as to reach
  idle at touchdown. A/T FMA annunciates RETARD.
  the A/T automatically disengages approximately 2 seconds after
  touchdown.
  the A/P must be manually disengaged after touchdown. Landing rollout is
  executed manually after disengaging the A/P.
  
  
  Rollout
  
  ROLLOUT arms when LAND 2 or LAND 3 annunciates.
  At approximately two feet radio altitude, rollout activates:
  
  
  ROLLOUT replaces the VOR/LOC roll flight mode annunciation
  the autopilot controls the rudder and nose wheel steering to keep the
  airplane on the localizer centerline.
  rollout guidance continues until a full stop or until the autopilots are
  disengaged.