Speed measuring system

Claim 1

IN A SYSTEM FOR MEASURING THE SPEED OF MOTION OF A BODY IN A GIVEN HORIZONTAL DIRECTION, THE COMBINATION COMPRISING A SOURCE OF SINGLE-FREQUENCY CONSTANT-AMPLITUDE WAVE ENERGY ASSOCIATED WITH SAID BODY AND PROJECTING WAVE ENERGY DOWNWARDLY OVER A RELATIVELY BROAD BEAM, A PAIR OF RECEIVING ANTENNAS ASSOCIATED WITH SAID BODY AND DOWNWARDLY DIRECTED FOR RECEIVING CORRESPONDING ECHOES OF THE WAVE ENERGY PROJECTED BY SAID SOURCE, SAID RECEIVING ANTENNAS HAVING A KNOWN MUTUAL SEPARATION MEASURED IN SAID HORIZONTAL DIRECTION, A PAIR OF DETECTORS COUPLED TO SAID RESPECTIVE RECEIVING ANTENNAS FOR SENSING MODIFICATION OF SAID PROJECTED WAVE ENERGY IN THE ECHO PROCESS, TIME DELAY MEANS COUPLED TO AT LEAST ONE OF SAID DETECTORS FOR PROVIDING A KNOWN TIME DELAY TO ONE DETECTED ECHO RETURN RELATIVE TO THE OTHER, CORRESPONDENCE SENSING MEANS HAVING SUPPLIED THERETO SAID RELATIVELY DELAYED DETECTED ECHO RETURNS, MEANS FOR ADJUSTING THE AMOUNT OF SAID SEPARATION TO BRING ABOUT CORRESPONDENCE, AND MEANS DEPENDENT UPON THE QUOTIENT OF SAID SEPARATION AND SAID TIME DELAY FOR DETERMINING SAID SPEED.