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In Situ and Remote Methods for Resource Characterization Chapter | 7 165

ADV estimates the three components of velocity (i.e. in the x, y, and z directions)
based on these data. ADVs are designed with various signal frequencies, suitable
for various ranges of current speeds.
ADVs are popular in laboratory flume studies [7] and are particularly useful
for characterizing turbulence due to their HF sampling (e.g. 50 Hz [8]). In
the oceanic environment, ADVs are gaining popularity due to their ability to
quantify turbulence. For example, the Nortek Vector 3D is capable of measuring
velocities up to 7 m/s and, due to the HF sampling associated with ADVs, can
measure wave orbital velocities. However, ADVs tend to be deployed in very
shallow nearshore environments.

7.1.4 Acoustic Doppler Current Profiler
If a profile of the water column is desired, it would be necessary to deploy a
string of current meters (Section 7.1.2) distributed over the water column (e.g.
[9]). However, for most practical measurements of marine currents over the
water column, particularly when the vertical component of velocity is required,
the use of current meters has been more-or-less superseded by the advent, in the
1980s, of ADCPs (Fig. 7.5).

Principal of Operation
The ADV that was introduced in Section 7.1.3 uses a converging beam pattern
(Fig. 7.4), and so can only sample a small volume of water at the point where the
beams converge. By contrast, an ADCP uses a diverging beam pattern (Fig. 7.5),
usually based on at least three beams, to resolve velocities in three dimensions.

FIG. 7.5 Four-beam (left) and five-beam (right) acoustic Doppler current profilers (ADCPs). The
five-beam ADCP is discussed in Section 7.2.3.