Patent ID: 7031224

Claim:
A buoy-to-sailboat distance indicator system for determining the distance between a buoy and at least one boat both floating in a common body of water, comprising: a buoy transmitter deployed on said buoy, further comprising: a speed of sound calibrator for producing a measurement of the speed of sound through said body of water; a radio transmitter for producing a radio signal transmitted through the air above said body of water; an acoustic transmitter for producing an acoustic signal transmitted from said buoy through said body of water; and a transmitter CPU for receiving said measurement of the speed of sound, calculating the trigger times and triggering said radio transmitter and said acoustic transmitter to transmit said radio signal above and said acoustic signal through said body of water, respectively, such that both arrive at a predetermined distance across said body of water simultaneously; and at least one boat receiver deployed on one of said boats, further comprising: a radio receiver for receiving said radio signal transmitted through the said air above said body of water; an acoustic receiver for receiving said acoustic signal transmitted through said body of water; a receiver CPU for determining the relative arrival time between said radio signal and acoustic signal, and determining thereby the distance of said boat from said buoy relative to said predetermined distance; and an information display for displaying said distance of said boat from said buoy relative to said predetermined distance.