The U.S. Geological Survey tested and refined tethered-platform designs for measuring streamflow. Platform specifications were developed, radio-modem telemetry of acoustic Doppler current profiler (ADCP) data and potential platform-hull sources were investigated, and hulls were tested and evaluated.
Different platforms, which included a variety of hull configurations, were tested for drag and stability at the U.S. Geological Survey tow tank and at a field site below a reservoir. The testing indicated that, although any of the designs could be used under certain conditions, trimaran designs provided the best all-around performance under a range of conditions. The trimaran designs housed the ADCP in the center hull; this resulted in lower drag than the catamaran designs and retained the stability advantage of catamarans over monohull designs. Waterproof radio modems that operate at 900 megahertz were used to communicate wirelessly with instruments at high baud rates.
A tethered-platform design with a trimaran hull and 900-megahertz radio modems is now commercially available. Continued field use has resulted in U.S. Geological Survey procedures for making tethered-platform discharge measurements, including methods for tethered-boat deployment, moving-bed tests, and measurement of edge distances.
