Analyze Data#

In the third tab of OCEANLYZ GUI, analysis parameters are defined and data analysis is started.

For technical detail visit https://oceanlyz.readthedocs.io

_images/Figure_GUI_Analyze_Data_Tab.png

Figure: Analyze Data tab#

Panel 1#

Panel 1 contains parameters that should be set for any analysis.

Input data type (InputType=’waterlevel’)
Define input data type
InputType=’waterlevel’: Input data is water level or water depth in (m)

If InputType=’waterlevel’ then OutputType=’wave’

InputType=’pressure’: Input data are water pressure measured by a pressure sensor at sensor depth in (N/m^2)

If InputType=’pressure’ then OutputType=’waterlevel’ or OutputType=’wave+waterlevel’

Output data type (OutputType=’wave’)
Define output data type
OutputType=’wave’: Calculate wave properties from water level or water depth data
OutputType=’waterlevel’: Calculate water level data from water pressure data measured by a pressure sensor
OutputType=’wave+waterlevel’: Calculate waves properties and water level data from water pressure data measured by a pressure sensor
Analysis method (AnalysisMethod=’spectral’)
Analysis method
AnalysisMethod=’spectral’: Use spectral analysis method / Fast Fourier Transform
AnalysisMethod=’zerocross’: Use zero-crossing method
Number of burst (n_burst=1)
Number of burst(s) in the input file
n_burst = (total number of data points)/(burst_duration*fs)
Example:
Assume data are collected for 6 hours at a sampling frequency of fs=10 Hz
If data are analyzed at intervals of 30 minutes then there are 12 bursts (6 hours/30 minutes=12 bursts)
For 12 bursts of data, which each burst has a duration of 30 minutes, and collected at sampling frequency of fs=10 Hz
burst_duration=(30 min * 60) = 1800 seconds
total number of data points=(number of burst)*(duration of each burst)*(sampling frequency)
total number of data points=(n_burst)*(burst_duration)*(fs)
total number of data points=12 * 1800 * 10
Duration of each burst (burst_duration=1024)

Duration time that data collected in each burst in (second)

Sampling frequency (fs=2)

Sampling frequency that data are collected at in (Hz)

Panel 2#

Panel 2 contains parameters that are required for spectral analysis. In other words, these parameters are required only if analysis method is set to spectral.

Minimum frequency cut-off (fmin=0.05)
Minimum frequency to cut off the spectrum below that, i.e. where f<fmin, in (Hz)
Results with frequency f<fmin will be removed from analysis
It should be between 0 and (fs/2)
It is a simple high pass filter
Only required if AnalysisMethod=’spectral’
Maximum frequency cut-off (fmax=1e6)
Maximum frequency to cut off the spectrum beyond that, i.e. where f>fmax, in (Hz)
Results with frequency f>fmax will be removed from analysis
It should be between 0 and (fs/2)
It is a simple low pass filter
Only required if AnalysisMethod=’spectral’

Panel 3#

Panel 3 contains parameters that are required for pressure data analysis. In other words, these parameters are required only if input data type is set to pressure.

fmaxpcorr calculation method (fmaxpcorrCalcMethod=’auto’)
Define if to calculate fmaxpcorr and ftail or to use user defined
fmaxpcorrCalcMethod=’user’: use user defined value for fmaxpcorr
fmaxpcorrCalcMethod=’auto’: automatically define value for fmaxpcorr
Only required if InputType=’pressure’ and AnalysisMethod=’spectral’
Pressure response factor for (f > fmaxpcorr), (Kpafterfmaxpcorr=’constant’)
Define a pressure response factor, Kp, value for frequency larger than fmaxpcorr
Kpafterfmaxpcorr=’one’: Kp=1 for frequency larger than fmaxpcorr
Kpafterfmaxpcorr=’constant’: Kp for f larger than fmaxpcorr stays equal to Kp at fmaxpcorr (constant)
Kpafterfmaxpcorr=’nochange’: Kp is not changed for frequency larger than fmaxpcorr (Not implemented yet)
Only required if InputType=’pressure’ and AnalysisMethod=’spectral’
Minimum frequency for fmaxpcorr (fminpcorr=0.15)
Minimum frequency that automated calculated fmaxpcorr can have if fmaxpcorrCalcMethod=’auto’ in (Hz)
If fmaxpcorrCalcMethod=’auto’, then fmaxpcorr will be checked to be larger or equal to fminpcorr
It should be between 0 and (fs/2)
Only required if InputType=’pressure’ and AnalysisMethod=’spectral’
Maximum frequency for fmaxpcorr (fmaxpcorr=0.55)
Maximum frequency for applying pressure attenuation factor in (Hz)
Pressure attenuation factor is not applied on frequency larger than fmaxpcorr
It should be between 0 and (fs/2)
Only required if InputType=’pressure’ and AnalysisMethod=’spectral’
Pressure sensor height from bed (heightfrombed=0.0)
Pressure sensor height from a bed in (m)

Leave heightfrombed=0.0 if data are not measured by a pressure sensor or if a sensor sits on the seabed | Only required if InputType=’pressure’

Panel 4#

Panel 4 contains parameters that are optional.

Water density (Rho=1000)
Water density (kg/m^3)

Only required if InputType=’pressure’

NFFT (nfft=512)
Define number of data points in discrete Fourier transform
Should be 2^n
Results will be reported for frequency range of 0 <= f <= (fs/2) with (nfft/2+1) data points
Example: If fs=4 Hz and nfft=512, then output frequency has a range of 0 <= f <= 2 with 257 data points
Only required if AnalysisMethod=’spectral’
Separate wind sea and swell waves (SeparateSeaSwell=’no’)
Define if to separate wind sea and swell waves or not
SeparateSeaSwell=’yes’: Does not separate wind sea and swell waves
SeparateSeaSwell=’no’: Separates wind sea and swell waves
Maximum swell frequency (fmaxswell=0.25)
Maximum frequency that swell can have (It is about 0.2 in Gulf of Mexico) in (Hz)
It should be between 0 and (fs/2)
Only required if SeparateSeaSwell=’yes’ and AnalysisMethod=’spectral’
Minimum swell frequency (fpminswell=0.1)
Minimum frequency that swell can have (it is used for Tpswell calculation) in (Hz)
It should be between 0 and (fs/2)
Only required if SeparateSeaSwell=’yes’ and AnalysisMethod=’spectral’

Start Analysis#

To start analysis click Start Analysis button. Note: depend on the size of data and analysis method, analysis may take a while.