Raw data review (QA1)

Raw data review

This review is a comparison of data between beams, between bins and over time to determine possible anomalies. Note that consideration of spatial and temporal trends may be informed by data from other sensors e.g. meteorological, wave or CTD sensors. The following characteristics should be examined:

1. Correlation coefficient
   1. minimum threshold to identify bad data
2. Echo intensity
   1. false target / “fish” detection to identify bad data
3. Orientation (heading, pitch, roll) and depth (if sensor installed)
   1. deployment as planned?
   2. indentify specific changes or periodic motion
4. Along beam velocity
   1. data return rate
   2. phase wrapping for pulse-pulse coherent observations
   3. periodicity indicating waves or oscillatory motion
   4. distribution outliers
   5. burst variance spatial and temporal trends
5. Temperature and salinity (if sensors installed)
   1. indication of changes in local stratification and/or internal wave activity
6. Earth coordinate velocity
   1. may need to be derived from along-beam velocity
   2. bin mapping if ADCP orientation isn’t vertical
   3. error velocity from 4-beam instruments
   4. comparison with ambiguity velocity to check for possible phase wrapping
   5. burst variance spatial and temporal trends
   6. shear over observation range

Structure function calculation

1. Set evaluation spatial scale
   1. options dependent on bin size and beam range
   2. theory based on homogenous isotropic turbulence
2. delta b calculation
   1. determine percentage of instances in burst when delta b can be calculated for separation distance delta r at a location r
   2. distribution of delta b / delta b squared values – impact of outliers and resilience of mean