1. ADCP Waves Raw Data Processing
Greg Dusek
Harvey Seim, Sara Haines, Chris Calloway
Dept of Marine Sciences
UNC Chapel Hill

2. ADCP Directional Wave Processing
ADCP Raw Data
ADCP Directional Wave Processing
Splitter
(Python)
Currents Data
Waves Data
Proc Waves
(Python)
pressure.txt
orbitals.txt
ranges.txt
sysinfo.txt
Specmultiplot
(matlab)
Radial to uvw
(matlab)
Data structure
Ready for DIWASP
DIWASP
(matlab)
Directional Wave
Spectral Matrix

3. DIWASP Directional Wave Spectral Toolbox
Created by David Johnson (Centre of Water Research, University of Western Australia)
Edited by Greg Dusek as of 08/2007
Changed matlab spectral density function csd to cpsd
Added the ability to input the along beam radial velocities
Added the ability to plot multiple spectra on one page
Inputs
Surface Elevation
Pressure
Current Velocity Components
Surface Slope Components
Water Surface Vertical Velocity
Water Surface Vertical Acceleration
Along Beam Radial Velocities (recently added)

4. DIWASP cont. Estimation Methods Available Can Also Choose:
DFTM- Direct Fourier Transform Method
EMLM-Extended Maximum Likelihood Method
BDM-Bayesian Direct Method
IMLM-Iterated Maximum Likelihood Method
EMEP-Extended Maximum Entropy Method
Can Also Choose:
Directional Resolution
Frequency Resolution
Number of Iterations Performed
Type of graphical output

5. Current Analysis Looking at 4 distinct test cases at Bogue Inlet Pier
1200khz ADCP in 8m of water
Which estimation methods provide the best results
How the DIWASP generated wave spectra compare to those created by RDI’s Wavesmon
Comparison at the 8 meter Duck Pressure Array
Data from the Duck Pressure Array and an 1200khz RDI ADCP in the same location
Comparison of spectra from the ADCP processed by RDI’s Wavesmon and processed by DIWASP to spectra processed independently from the 8 meter array
Comparison between ADCP and AWAC (in progress)
RDI ADCP and Nortek AWAC in the same location at the Bogue Inlet Pier
Comparison of the spectra generated through the proprietary software of both instruments to those generated through DIWASP

6. Bogue Pier Test Cases Looking at 4 test cases from ADCP at Bogue Pier
Large Amplitude, Long Period Waves
Large Amplitude, Small Period
Small Amplitude, Long Period
Small Amplitude, Small Period
For each test case:
Two examples of each case
Look at IMLM and EMEP estimation methods
Use UVW and Pressure data, Range data (Surface Elevation), and along beam Radial Velocity (transferred to Surface Displacement)
Compare Results to Wavesmon generated spectrum
Used a directional resolution of 2 degrees, a frequency resolution of .01Hz and iterations set to 100 for EMEP, and set to 3 for IMLM
Used the default settings for Wavesmon: directional resolution of 4 degrees, a frequency resolution of Hz and the IMLM method with 1 iteration

7. Bogue Inlet Pier – 1359 March 2, 2007 Large Amplitude, Long Period

8. Bogue Inlet Pier – 1359 March 2, 2007 Large Amplitude, Long Period

9. Bogue Inlet Pier – 1359 March 2, 2007 Large Amplitude, Long Period

10. Bogue Inlet Pier – 1359 March 2, 2007 Large Amplitude, Long Period

11. Bogue Inlet Pier – 1359 March 2, 2007 Large Amplitude, Long Period
EMEP uvw
SigH (meters): 2.19
peak period (seconds):
Dir of peak period: 6
Dominant Direction: 10
IMLM uvw
Dir of peak period: 2
Dominant Direction: 352
EMEP Radial Velocities
SigH (meters): 1.84
Peak period (seconds):
Dir of peak period: 270
Dominant Direction: 12
EMEP Range
SigH (meters): 2.03
peak period (seconds):
Dir of peak period: 6
Dominant Direction: 8
IMLM range
Dir of peak period: 14
Dominant Direction: 14
Wavesmon output
SigH (meters): 2.16
peak period (seconds):
Dir of peak period: 355
Dominant Direction: 359

12. Bogue Inlet Pier – 1400 April 4, 2007 Large Amplitude, Small Period

13. Bogue Inlet Pier – 1400 April 4, 2007 Large Amplitude, Small Period

14. Bogue Inlet Pier – 1400 April 4, 2007 Large Amplitude, Small Period

15. Bogue Inlet Pier – 1400 April 4, 2007 Large Amplitude, Small Period

16. Bogue Inlet Pier – 1400 April 4, 2007 Large Amplitude, Small Period
EMEP uvw
SigH (meters): 1.00
peak period (seconds): 5
Dir of peak period: 270
Dominant Direction: 14
IMLM uvw
SigH (meters): 0.99
Dir of peak period: 36
Dominant Direction: 38
EMEP Radial Velocities
SigH (meters): 0.86
Peak period (seconds): 5
Dir of peak period: 24
Dominant Direction: 22
EMEP Range
SigH (meters): 0.92
peak period (seconds): 5
Dir of peak period: 28
Dominant Direction: 30
IMLM range
Dir of peak period: 30
Wavesmon output
SigH (meters): 1.05
peak period (seconds): 4.92
Dir of peak period: 15
Dominant Direction: 27

17. Analysis EMEP method seems to generally outperform IMLM
Using uvw velocities works fairly well with long period waves (swell conditions) but has trouble with short period waves (wind conditions)
Using the ranges seems to perform very well with shorter period waves increasing to some period relative to the depth. A this point the aperture becomes too small to resolve the wave direction.
The radial velocities appear to work fairly well, however there is an unexplained consistent loss of sig wave height. This does not appear in the following example of the 8m array ADCP.
Wavesmon appears to perform fairly well in all conditions

18. 8 Meter Duck Pressure Array
Data from RDI ADCP and Pressure Array
RDI ADCP
Data processed by RDI’s Wavesmon software
Data processed through python and matlab waves toolbox, using DIWASP to generate spectra
8m Pressure Array
Data processed by independent ACE FRF method
Comparison of data over time
Analysis of a two day period sampling every 3 hours, Feb at 1900 to Feb at 1900

19. Duck, NC at ACE FRF Significant Wave Height (Feb 01 2007, 1900-Feb 03 2007, 1900)

20. Duck, NC at ACE FRF Peak Period (Feb 01 2007, 1900-Feb 03 2007, 1900)

21. Duck, NC at ACE FRF Direction of Peak Period (Feb 01 2007, 1900-Feb 03 2007, 1900)

22. Duck, NC at ACE FRF Dominant Direction (Feb 01 2007, 1900-Feb 03 2007, 1900)

23. Duck, NC at ACE FRF 3D Wave Spectra Feb 01 2007, 1900

24. Duck, NC at ACE FRF 2D Wave Spectra Feb 01 2007, 1900

25. Duck, NC at ACE FRF 3D Wave Spectra Feb 01 2007, 1900

26. Duck, NC at ACE FRF 2D Wave Spectra Feb 01 2007, 1900

27. Duck, NC at ACE FRF 3D Wave Spectra Feb 03 2007, 1000

28. Duck, NC at ACE FRF 2D Wave Spectra Feb 03 2007, 1000

29. Duck, NC at ACE FRF 3D Wave Spectra Feb 03 2007, 1000

30. Duck, NC at ACE FRF 2D Wave Spectra Feb 03 2007, 1000

31. Analysis
The EMEP method using the radial velocities appears to provide a very good estimation of the directional wave spectrum over a 2 day period.
The IMLM method with the radial velocities consistently performs poorly.
In comparison to the 8m array this method is generally in agreement in terms of sig wave height, peak period and direction
Using the uvw velocities the swell waves can be fairly well estimated, however there is no directionality to the wind waves
Using the ranges the wind waves are somewhat resolved, but the swell waves are less resolved directionally
The second case shown is a good example to both wind and swell conditions existing simultaneously and from different directions. The EMEP radial velocities is fairly accurate when compared to the 8m array in this example, as is Wavesmon. However, the range and uvw estimation methods have significant trouble resolving both types of waves.

32. Summary
The ADCPs at both Bogue Pier and at the FRF are at roughly the same depth and are both 1200khz types
The results from the Bogue Pier case studies provide for a good basis for understanding which type of estimation method and which sets of data can provide the best estimations of the wave field
The results from the comparison at the 8m array have shown that the EMEP method with the radial velocity data seems to perform well in a variety of conditions including those with swell and wind waves present
Wavesmon has shown to perform well in estimating the wave field in a variety of conditions, however, the limitations and “black-box” aspect of the software makes having a functional alternative desirable
The next step will be to compare the independently processed 8m array spectra to the spectra generated from running the raw data through our processing tool box.
At Bogue Pier we now have data from a Nortek AWAC instrument that can be compared to the output generated by the ADCP at the same location. This work is in progress.