ADCP Environment

The best sampling strategy will depend on the environmental flow regimes, specifically the following parameters: ​

1. Time and length-scales​

   Compute these to horizontal and vertical​ in order to make the best choices for:

   1. Sampling time​
      1. Repetition rate​
      2. Sample as fast as possible (spread out the spectral density of noise)​
      3. Optimize trade off against power/storage​
   2. Bin size​
      1. No smaller than advective lengthscale if using across beam methods​
      2. Factor this into ambiguity velocity​
      3. Links between bin size/nominal velocity accuracy, sub-pings (averaging across pings) duration of data aggregation (burst sampling)​
   3. No of samples ​
      1. will be determined by whether sampling is burst vs continuous​
      2. Note burst periods can save power and reduce required storage capacity, but must be carefully chosen to capture the required dynamics​
2. Time averaging (important to specify whether the averaging is over the ensemble period for the full deployment period.)​
3. Max expected flow velocities used to set the ADCP ambiguity velocity ​
4. Account for likely SNR​
   1. scatterers if known. ​
   2. Water velocities; energy.​
   3. Likely turbulence ROT 10%​
5. Stratification for stratified environments​
   1. Stratified flows can have significant background shear (boundary layer or otherwise)​
   2. Estimate expected shear if possible: in the presence of shear, any variation in instrument orientation (pitch, roll or heading) will result in velocity differences due to background shear not being correctly removed, leading to bias in epsilon estimates.​
6. Waves​
   1. Expected influence of wave field Stokes drift on surface measurements​
   2. Consider becoming familiar with wave removal algorithms.​

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