1. OC3570 Operational Oceanography
“Comparison of ADCP Velocities”
LT Mike Rost
17 March 2004

2. ADCP (ology) Frequency and resolution Narrow Band vs Broadband
Who is this Doppler guy?
Gates and Bins (it’s a round up)
Independence
Freq Improves resolution, decreases penetration
BW important for measuring doppler shift, but increases uncertainty of measurement if too large.
Shift in Freq gives vector information about scatters in water column
Gates are time slices listening for returns, diving up the water column into bins.
Gates determined by transmit pulse width, and effect cell size.
Gates and bins overlap temporally, thus averaged velocities in a bin are not independant

3. Bay Locations

4. Distance from Central Point

5. Interpreting the Data
TRBM was vector averaged into equal size bins with same center depth as VADCP
TRBM was time averaged to 5 minute increments to match VADCP data.
TRBM is up pointing vs VADCP down pointing nature
25 hours of data looked at
TRBM locations 123 meters of water
TRBM bins 120 to 22 meters centered at 2 meter increments
ADCP bins 19 to 99 meters every 8 meters
TRBM 1 minute averages
ADCP 5 minute averages of about 300 pings

6. Raw TRBM velocity averages
Magnitude U V

7. ADCP Velocities
Magnitude U V

8. Reanalysis and Comparison

9. ADCP AutoCorrelation

10. TRBM Autocorrelation

11. U velocity Crosscorrelation

12. V velocity Crosscorrelation

13. Questions?