Posted on 15.10.2011 - 05:29 UTC in SURVEY NEWS by Rons_ROV_Links
Oceanscience develop multi-profiler instrumentation boat to compare Teledyne RD Instruments and SonTek/YSI Acoustic Doppler Current Profilers (ADCPs)
Researchers at L'Institut de recherche d'Hydro-Québec (Hydro-Québec Research Institute, or IREQ) wanted to compare the performance of several acoustic Doppler current profilers commonly used for river discharge measurements. As new instruments become available, comparison measurements between new profilers and well known "benchmark" profilers are important to quickly validate the new instrumentation for field use. This process is often made difficult in the river environment where the profilers are deployed on small tethered boats; the boats are usually of varying design for the different profilers, which may bias comparison measurements made using them. In addition, as a result of size limitations it is not possible to deploy any two profilers simultaneously on the same tethered boat.
Oceanscience engineers worked with IREQ engineer Catherine Guay to come up with an easy and useful way to compare the latest acoustic profilers, and it quickly became clear that the remote controlled Q-Boat 1800P was the best option as a comparison platform. The Q-Boat is large enough to accommodate two profilers at once, without compromising their individual installation geometry, and courtesy of its twin high power outdrives the boat can handle 4m/s (13fps) water velocities even with two profilers on board. Although acoustic interference may preclude use of the profilers simultaneously, the next best option of immediately switching from one profiler to the other on consecutive transects on an identical platform offers the best available solution for comparison measurements.
Instead of the usual single large instrument well, twin instrument wells were installed with a smaller forward well for the smaller diameter instruments. The spacing and placement of the wells was optimized to minimize any magnetic interference or bias errors that may disproportionately affect either profiler, particularly important when compass performance is critical.
The Q-Boat 1800P was designed to allow remote discharge measurements using ADCPs in flood conditions, and has been used all around the world, offering flexibility and safety for hydrologists wishing to measure discharge in conditions that may be otherwise unsafe or even impossible.
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