With new development in technologies, proliferation of manufacturers, and expanded applications of acoustic Doppler current profiling instruments, the need for proper sensor test procedures becomes increasingly important. This report documents a towing basin speed measurement verification procedure that NOS has adopted for the past decade and a summary of verification results of forty-one cases consisting of twenty-nine individual sensors. These sensors include fourteen RD Instruments acoustic Doppler current profiler (ADCP) units (seven 600 and seven 1200 KHz units) and fifteen SonTek acoustic Doppler profiler (ADP) units (three 500 and twelve 1500 KHz units). Some of these sensors were tested repeatedly on different dates prior to deployment. Tow carriage speeds varied from 5 cm/s to 200 cm/s and were used as references for comparison. The speed differences between sensor readings and carriage references are expressed in terms of mean, standard deviation, and percentage of reference speed. Overall, RDI ADCPs have smaller mean speed differences and standard deviations compared with SonTek ADPs of similar frequencies. There is a larger sensor-to-sensor variation among SonTek units, especially among the 500 KHz ADPs. Except for the SonTek 500 KHz units, the standard deviation and percentage error of the tested sensors were close to manufacturer's specifications. Small zero offsets, on the order of 1 cm/s for ADCPs, 2 cm/s for 1500 KHz ADPs, and 5 cm/s for 500 KHz ADPs, were measured. The test results of both sensor types repeat well over time. To aid in the discussing of test procedure and results, a brief review of related ADCP and ADP design and operational parameters are also included in this report.

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The National Oceanic and Atmospheric Administration's (NOAA) Center for Operational Oceanographic Products and Services (CO-OPS) currently maintains twenty operational Physical Oceanographic Real-Time System (PORTS®) observatories throughout United States coastal regions. To expand its measurement capabilities, CO-OPS recently developed and tested a real-time wave measurement system featuring a Nortek 1-MHz Acoustic Waves and Current Profiler (AWAC). The test system consisted of a bottom platform assembly and a surface communications buoy. The bottom assembly contained the AWAC, a LinkQuest omnidirectional acoustic bottom modem, batteries, and a Benthos acoustic release with tethered pop-up float. The surface buoy supported a LinkQuest acoustic surface modem, an Iridium communication system, solar cells, battery, GPS receiver, and temperature and voltage sensors. A 35-day field test of this real-time wave system was conducted from June 16 through July 20, 2011, in shallow water (19 m) Atlantic Ocean region approximately 10 nautical miles off of the coast of Virginia. The site was in close proximity ( approximately 190 m) to a Datawell Waverider buoy that is maintained by the Scripps Institute of Oceanography CoastalData Information Program (CDIP). During the field test, bulk wave parameters, including significant wave height and average wave period, were transmitted real-time every 30 minutes. Raw data recorded internally on the AWAC included 'burst' samples of 2048, 2-Hz values, collected every half hour. After the AWAC was recovered at the end of the field test, raw data were downloaded and used to calculate half hourly power spectra, both non-directional and directional. The resulting field test data were used to compare measurements from the AWAC and Datawell Waverider. A description of the real-time AWAC waves system and field test performance is presented, along with a comparison of AWAC versus Datawell buoy measurements for both half hourly wave bulk parameters and frequency spectra.