Near Shore - Water Velocity Profiles
[II-B2]
I want to make measurements in the ocean. [change]
My area of interest is the near shore... [change]
...and involves profiles of water velocity. [change]
SonTek/YSI makes both the Acoustic Doppler Profiler (ADP) and the Pulse-Coherent ADP (PC-ADP) for profiles of
water velocity. The ADP is for larger-scale phenomena (resolution
<1.0 cm/s), while the PC-ADP is for very high resolution work
(<0.1 cm/s) that is typically near the bottom boundary.
For ADPs, there are two basic
questions that quickly get us to the most appropriate system:
- What profiling range is required?
The ADP is available in five frequencies, with nominal ranges of 6, 25, 40, 90, and
160 m. These are the expected "medium" ranges under typical conditions. In
some cases the range will be less, in others more.
- How is the ADP to be deployed (e.g., on the bottom, on a mooring, from a boat)?
If the ADP is to be deployed on the bottom, or in a fixed location, then a compass/tilt
sensor might prove a useful addition for installation, and also for later analysis to see
if the package has moved. If the ADP is to be deployed on a mooring, then a compass/tilt
is essential for proper vector averaging. If it is to be deployed from a moving platform
(e.g., a boat), then we need to account for the motion of the platform whether through the
use of a DGPS system or our bottom-tracking feature (or both).
The PC-ADP
(at left) is capable of very high resolution
measurements, with cell sizes as small as 1.6 cm and data rates as high as 2 Hz. The
PC-ADP is designed for deployment from a fixed platform, most commonly looking downward
with a range of 1 to 2 m.
There is a complete suite of Windows-based software for the ADPs, including
post-processing and three different application-specific data acquisition programs.
Any ADP (or PC-ADP) can be configured for real-time
monitoring or for autonomous deployments with on board logging and power. Also, either
system can be configured with a variety of external sensors, including pressure,
conductivity, temperature, turbidity, etc.
ADPs equipped with pressure sensors can be configured with software that calculates
wave statistics such as significant wave height and peak period.
