Ultrasonic measuring system

An ultrasonic measuring apparatus for a vehicle comprising a first ultrasonic transducing means including first, second and third ultrasonic transducers disposed at 120.degree. intervals in a horizontal plane about a first vertical axis disposed adjacent a front end of the vehicle, each of said first, second and third ultrasonic transducers transmitting ultrasonic waves to a road surface at a down-angle relative to the road surface and receiving reflected waves from the road surface;

• a second ultrasonic transducing means including fourth, fifth and sixth ultrasonic transducers disposed at 120.degree. intervals in a horizontal plane about a vertical axis disposed adjacent a rear of the vehicle, each of said fourth, fifth and sixth transducers transmitting ultrasonic waves to a road surface at a down-angle relative to the road surface and receiving reflected waves from the road surface;
• said first transducer and said fourth transducer sending and receiving ultrasonic waves in directions 180.degree. apart, said second transducer and said fifth transducer sending and receiving ultrasonic waves in directions 180.degree. apart and said third transducer and said sixth transducer sending and receiving waves in directions 180.degree. apart;
• and
• computing means for computing three first speed vectors in three first directions obtained by said first ultrasonic transducing means and computing three second speed vectors in three second directions corresponding to the three first directions obtained by said second ultrasonic transducing means and computing a two-dimensional speed by synthesizing said first and second speed vectors.