A DVL is an acoustic Doppler instrument, and is similar to the acoustic Doppler current profiler (ADCP). It has acoustic beams oriented in a diverging, convex configuration.
However, it differs from ADCPs in its ability to estimate the velocity relative to the bottom (Earth being the frame of reference). This is done by estimating the velocity along each beam relative to the bottom.
Operating alone, the DVL provides a means to estimate a distance travelled and calculate the current position with simple “dead reckoning” navigation. However, for underwater AUV and ROV operations, this is not sufficient and a DVL is typically one of multiple inputs into a navigation solution. In addition to the DVL, a navigation solution may include inertial sensors, acoustic positioning, heading, depth, and altimeter. These estimates are then passed through estimator algorithms/filters such as a Kalman filter to arrive at an estimate of position.
The value of the DVL into such a solution is that it has zero mean bias and does not drift. The DVL is the critical because without it, the position would drift substantially with time. The DVL helps limit the cumulative errors of a complete navigation solution.
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Download the Nortek DVL Specification
Why are we ideally positioned to provide DVLs?
Nortek provides a DVL which is designed and fabricated by an organization with a solid history working in the field of acoustic Doppler instrumentation. Acoustic Doppler navigation falls within Nortek’s core competency and the DVL is the latest instrument operating from Nortek’s so-called AD2CP platform. This is a modern hardware platform with powerful processors. This platform is undeniably state-of-the-art due to its features of low power, exceptional range, accuracy and small package size.
Often when comparing competing technologies, one finds that improving the skill in one functionality compromises that of another. So there is no real technical leap. Nortek’s DVL does not have hidden compromises. A comparison across the industry shows that the Nortek DVL exceeds on all the important specifications.
We would not be providing the complete picture if we did not mention that we have been down this road when we provided Puma Ocean Racing a pure water track DVL when it competed in the around-the-world, Volvo Ocean Race (2011-2012). The sensor permitted them to accurately measure through water speed for a performance sailing yacht. The high accuracy sensor permitted the ability to estimate "leeway" and realtime currents - a first in performance sailing. Follow the PUMA link to Learn more.