Basic HTML Version
ACT Protocols for Wave Measurement Systems
July 2012
7
Nortek
- The Nortek AWAC (Acoustic Wave And Current)
profiler is an acoustic instrument based on the Doppler shift of
underwater sound waves. This instrument incorporates three
distinct technologies to measure and calculate current and
wave information: a pressure sensor, the acoustic transducers
for current estimation, and an independent vertically oriented
echo-sounder for Acoustic Surface Tracking (AST). The
AWAC transmits at three different frequencies (1 MHz, 600
kHz, and 400 kHz) to accommodate different deployment
depths, and estimates wave characteristics through a
combination of the three sensor measurements. The AWAC
allows users to select either the Maximum Likelihood method
or an SUV-based approach for wave calculations (SUV refers to Surface tracking and U,V
velocities). The output-message from both methods includes the First-5 Fourier coefficients.
The AWAC is also available with an internal wave processing module that can output finished
data products. This module was developed for applications where bandwidth and processing
platforms are limited.
Teledyne RDI
- The Waves ADCP (Acoustic Doppler Current Profiler) array resolves waves
incident from multiple directions while accounting for distortion due to the near-surface current
field. While deployed on the seabed, the ADCP Waves Array
measures up to a total of 12 radial velocity measurements to
quantify the near surface orbital fluctuations at up to 3 different
depth levels as input for the directional array processing and also
the primary non-directional spectra measurement. The system
can operate at 300, 600, and 1200 kHz. This uses up to 20
independent velocity measurements from depth cells located as
close to the surface as possible from the ADCP’s 4 beams. By
measuring near-surface wave orbital velocity variability across a
spatial array, the ADCP Waves Array blends both phase and
amplitude information to produce a time history of well-resolved
frequency-direction spectra. The Waves ADP also provides
surface tracking using redundant measurements of the non-directional spectra that are based
upon the acoustic range to the surface from each of the beams. It is also
capable of using PUV to resolve waves.
Valeport
- The MIDAS DWR (Directional Wave Recorder) & WTR (Wave
and Tide Recorder) use vertically oriented pressure sensors in combination
with Valeport electromagnetic current sensors (ECS) to calculate directional
spectra using the PUV method. The ECS measures electromagnetic current
oscillations with direction referenced to an internal flux gate compass.