Page 26: of Marine Technology Magazine (November 2017)

Acoustic Doppler Sonar Technologies ADCP & DVLs

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DVLs downward in different directions. to move along its track. Yet wind also forward motion.

Echoes are returned due to scattering causes motion across the vessel’s head- Minimizing sideslip due to winds and off the seabed. Because the DVL sonar ing. This downwind motion is called currents is a critical advantage in com- is aboard a moving vehicle, returning leeway. It can be seen by a sensor that petitive sailing. Measuring leeway can echoes carry a change in pitch; this is is looking at the water. The effect of lee- provide key information for winning. the Doppler Effect. way can be seen when the vessel’s wake A rapid and accurate system to measure

Generally, a different frequency shift is angled away from straight astern. leeway gives a navigator direct and im- is heard along each beam. Combining To counter leeway, sailboats with mediate feedback after course changes these readings tells how fast the vehicle multi-hull designs use adjustable dag- or daggerboard adjustments. This infor- is moving and in what direction. gerboards. These are retractable keels mation helps in tuning the boat’s use of that slide vertically through a slot in the wind power to move most ef

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