A Teledyne RDI 300 kHz Work Horse Acoustic Doppler Current Profiler (RDI ADCP) was mounted looking downward on the R/V Savannah. Sampling rate was dynamic (based on water depth) and varied between 2-3 seconds. Depth resolution was set to 2 meters. Vessel navigation data was also recorded by the acquisition software and included heading and location information.
Data were read from ADCP binary format using ADCPTools. Because bottom tracking did not work consistently over the cruises because of transects that extended over the upper slope, beyond the range of the ADCP, GPS data were also used to reference the velocities to earth. The processing steps were:
1. estimate surrogate bottom track velocities using GPS-derived vessel speed and heading,
2. find heading (-6.5 degrees) and pitch offsets (+3. degrees) that minimize difference between actual and surrogate bottom tracked velocities,
3. form estimate of bottom depth,
4. transform all data to earth coordinates and reference water velocities to earth using gps and bottom tracking,
5. bad flag data near-bottom and deeper based on water depth,
6. bad flag single ping solutions with error velocities > 0.3 m/s,
7. form 10 point (roughly 24 second) averages,
8. bad flag short-term averages where the absolute value of the vertical velocity exceeds 0.3 m/s, or where the absolute value of either of the horizontal velocity components exceeds 1.5 m/s,
9. form 12 point averages (roughly 5 minute averages) then interpolate to the regular time grid of 5 minutes.
Bad data are flagged with Not-a-Number (NaN).
Nelson, J., Edwards, C., Seim, H. E. (2016) Time series of current profiles from a vessel-mounted ADCP from R/V Savannah in the South Atlantic Bight (SAB) continental shelf off Long Bay, January-March 2012 (Long Bay Wintertime Bloom project). Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2016-02-15 [if applicable, indicate subset used]. http://lod.bco-dmo.org/id/dataset/638491 [access date]
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