Basic HTML Version
ACT Protocols for Wave Measurement Systems
July 2012
8
Reported Resolution/Accuracy/Range
Wave elevation
Period
Direction
Max Depth of
operation
Resolution/Accuracy (Range obs.) Res./Accuracy
Nortek
.01m / 0.1%
0.5-100s
0.1
o
/ 2
o
35m, 60m, 100m
FSI
.145x10
-3
range/.01% .4 s
.01
o
/ 2
o
23m
RDI
.025x10
-3
range/0.25%
1.8/3.5/7s
Min pd. for
depth
0.5
o
/ 2
o
80m
Valeport
.01m / 0.1% high acc. NA
0.1
o
/ 2
o
90m
4.2 Surface Moorings:
TRIAXYS
-
The TRIAXYS Directional Wave Buoy and TRIAXYS
Directional Wave Sensor (DWS) measure and calculate waves based on 6
degree of freedom inertial sensing of the hull motion.
The DWS is comprised
of 3D accelerometers and 3D rate sensors. In addition, the DWS is equipped
with a compass to determine wave directional spectra. These sensors
ultimately calculate the total displacement along the three orthogonal-axes of
the floating platform (x, y, z or North, East, Down).
This total displacement is
used to calculate both zero crossing wave statistics as well as spectral statistics
and directional spectra.
Output from the wave sensor includes approximately
20 statistical values, non-directional and directional spectra.
The DWS also
provides the first four Fourier directional coefficients from 0.030 Hz to 0.64
Hz in 0.005 Hz frequency spacing along with the corresponding energy
spectrum for further or alternative processing of the wave spectra.
The DWS is optimal for use in wave measurement from moored or free floating platforms,
operating in wave heights of 0.1 meters to 20 meters in height, and wave periods from 1.5
seconds to 30 seconds. The system can be used in any body of water from 2 meters deep to over
5000 meters in depth with appropriate hull platforms and proper mooring designs.
Datawell
-
The Directional Waverider MkIII is an orbital following,
stainless-steel buoy, moored with a 30 m long rubber cord. The vertical
wave displacement is measured by an accelerometer mounted on a
stabilized platform. Wave direction results from horizontal
displacements, determined by two more accelerometers, pitch and roll
sensors and a flux gate compass. The resulting system is robust, reliable,
low-power (0.3 W), highly accurate, and is applicable in any depth
(coastal and oceanic water). Output includes time series of the 3D
displacements (@ 1.28 Hz), and heave and directional spectra (First-5)
up to 0.58 Hz. Communication through HF link (up to 50 km), Argos,
Iridium, Orbcomm or GSM. In addition to the MkIII, Datawell
manufacturers a GPS based directional buoy, and a non-directional Waverider.