Shipboard ADCP current measurements (75 kHz) during RV METEOR cruise M190

Current velocities of the upper water column along the cruise track of R/V Meteor cruise M190 were collected by a vessel-mounted 75 kHz RDI Ocean Surveyor ADCP. The ADCP transducer was located at 5.0 m below the water line. The instrument was operated in narrowband mode (WM10) with a bin size of 8.00 m, a blanking distance of 4.00 m, and a total of 100 bins, covering the depth range between 17.0 m and 809.0 m. Beam velocities as recorded by the data acquistion software VmDAS were transformed to ship coordinates and after merging with the navigation data from the ship's Motion Reference Unit and Global Positioning systems into earth coordinates. Single-ping data / ping ensembles were screened for bottom signals and, where appropriate, a bottom mask was manually processed.
The ship's velocity was calculated from position fixes obtained by the Global Positioning System (GPS). Accuracy of the ADCP velocities mainly depends on the quality of the position fixes and the ship's heading data. Further errors stem from a misalignment of the transducer with the ship's centerline. Data post-processing included water track calibration of the misalignment angle (0.1185° +/- 0.4417°) and scale factor (1.0030 +/- 0.0084) of the Ocean Surveyor signal. The velocity data were averaged in time using an average interval of 60 s. Velocity quality flagging is based on following threshold criteria: abs(UC) or abs(VC) > 1.5 m/s, rms(UC_z) or rms(VC_z) > 0.3.