Quality Assurance/Control of ADCP Measurements

Provide justification for throwing out a measurement (in field notes if in field and during post processing). The person reviewing your measurement may not have been in the field with you! Provide justification for changing a threshold during post processing.

Have the following screens open during the measurement and the data QA/QC as needed:

• Discharge summary F12
• Ship track showing a good straight path for BT, GGA, and VTG track, look for irregularities, GPS/compass calibration issues, moving bed issues. Subsection any zigzags if necessary.
• Stick ship track, look for velocity errors (use the up/down arrow to change the depth). These may be screened out using thresholds.
• Earth velocity magnitude, look for gaps/white stripes in data, bad or no bottom depth, bad bins, etc. Gaps indicate a loss of bottom tracking. Look at edges and see if there are good bins at edge. This is needed for estimating the edge discharge. Subsection if necessary but make sure the distances are still okay.
• Water Speed vs. Boat Speed time series, look for spikes and dropouts, make sure boat speed is less than water speed. At the edges, the boat speed should be at rest.
• Heading/Pitch/Roll time series, look for spikes, etc. Pitch and roll should be close to 0 and less than 5 degrees on average.
• Tabular – Compass calibration
  • review BMG-GMG mag (bottom track – GPS track dist made good) should be close to zero, otherwise moving bed or GPS errors or compass is not calibrated
  • BC/GC should be close to 1
  • GC-BC should be close to 0 or 360 degrees.
• Tabular - GPS
  • Number of satellite changes should be low
  • Delta Altitude should be low, less than 3.5 m is acceptable
  • HDOP should be less than 4, around 2 is good.
  • Delta HDOP should be low
  • If many items appear red, GPS-derived velocity quality may be degraded.
• Earth Error Velocity (go to view – graphs – contour – velocity then right click on the screen and pick “data selection”. Pick Earth Error Velocity). Look for a very random distribution of error. Patterns or white stripes may indicate problems or possible velocity errors.
• Earth Projected Velocity (go to view – graphs – contour – velocity then right click on the screen and pick “data selection”. Pick Eearth projected Velocity). Press F2 to set the projected velocity to look for reverse flows, etc.
• Discharge Profile (to review estimated areas) (press F2 to average 5-10 ensembles and scroll through the profiles to see if default power fit extrapolation technique is okay).
• Press F3 for processing properties. Review the commands, edge estimates, offsets (such as transducer depth), thresholds. Check the thresholds. Thresholds may be adjusted to screen out bad data. In general we leave it as the default but adjustments are needed for streampro IPAQ measurements because the defaults are wrong. Adjusting thresholds is not recommended to fix your bad data…… getting a better measurement site is best when possible.
• Press F9 for system parameters -- the ADCP that was used, the water mode, bin size, etc.
• Press ctrl-F9 to average ensembles (during review)
• Press ctrl-G and ctrl-B to go back and forth between bottom track and GGA reference