Sidelooking laser altimeter for a flight simulator

The object of the invention is to provide an improved laser altimeter for a flight simulator which will allow measurement of the height of the simulator probe above the terrain directly below the probe tip. A laser beam 22 is directed from the probe 13 at an angle theta to the horizontal to produce a beam spot 20 on the terrain. The angle theta that the laser beam 22 makes with the horizontal is varied so as to bring the beam spot into coincidence with a plumb line 18 coaxial with the longitudinal axis of the probe 13. A television altimeter camera 30 observes the beam spot and has a raster line aligned with the plumb line 18. Spot detector circuit 26 coupled to the output of the TV camera monitors the position of the beam spot relative to the plumb line 18. An error signal is produced by computer 28 driving, via a servo motor 23, the laser beam optics so as to cause the beam spot to come into coincidence with the plumb line 18. At coincidence, computer 28 looks up in a table the altitude of the probe for the given angle theta and reads out the altitude to an altimeter readout 31.