#navigational_instrument  an instrument used for navigating
  supertype:  #instrument  a device that requires skill for proper use
  subtype:  #artificial_horizon__gyro_horizon__flight_indicator  a navigational instrument based on a gyroscope; provides an artificial horizon for the pilot
  subtype:  #compass__compas  navigational instrument for finding directions
     subtype:  #gyrocompass__gyrocompas  a compass that does not depend on magnetism but uses a gyroscope instead
     subtype:  #magnetic_compass  compass based on an indicator (as a magnetic needle) that points to the magnetic north
        subtype:  #compass_card__compasscard__mariner'scompas  compass in the form of a card that rotates so that 0 degrees or North points to magnetic north
  subtype:  #depth_finder__depthfinder  navigational instrument used to measure the depth of a body of water (as by ultrasound or radar)
     subtype:  #sonic_depth_finder__sonicdepthfinder__fathometer  depth finder for determining depth of water or a submerged object by means of ultrasound waves
  subtype:  #inclinometer  an instrument showing the angle that an aircraft makes with the horizon
  subtype:  #sonar__echo_sounder__asdic  a measuring instrument that sends out an acoustic pulse in water and measures distances in terms of the time for the echo of the pulse to return (sonar is SOund NAvigation Ranging; asdic is Anti-Submarine Detection Investigation Committee)

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