About wideband data processing
- Supported wideband systems
- Wideband and pulse compressed variables
- Calibrating a wideband echosounder
- Wideband analyses
Supported wideband systems
Echoview supports these wideband echosounders:
- EK80 family of echosounders
- Nortek
However, only the EK80 file formats offer full wideband calibration and wideband analysis capability with Echoview. The pulse compressed sample values from Nortek data files exist in a post-processed format (by the manufacturer) that is not available for further wideband processing.
Wideband and pulse compressed variables
Echoview supports two forms of wideband data types for wideband variables: complex or pulse compressed complex. Only these variables have underlying complex number ping samples for wideband analyses in Echoview.
To find the variable's data type, refer to the details dialog box. The raw variable name also indicates if the ping sample data is pulse compressed for that wideband variable.
Note: The ping samples from Nortek echosounders are real-valued. Hence, these variables are not available for wideband analyses in Echoview.
Underlying complex number ping samples
Echoview (raw and virtual) variables with wideband data types have complex numbers underlying the samples of each ping. Echoview uses these complex values for wideband analyses. You can export the underlying complex values, or process them directly in Echoview with the Code operator.
All wideband raw variables that share a common transducer and frequency have the same underlying complex data. For instance, the underlying complex values for Sv, Power and TS are the same. In contrast, the ping samples for Sv, TS or power variables are real values derived from the sonar equations specific to the echosounder.
Similarly, pulse compressed raw variables that share a common transducer and frequency band have the same underlying complex data, but pulse compressed.
For virtual variables, the underlying complex values are modified according to the algorithm of that variable.
Calibrating a wideband echosounder
In general, you may follow the procedure on the calibrating an echosounder page for calibrating your wideband echosounder with the Calibration Assistant (not available for wideband Sv).
Instead of a single frequency, the algorithms apply to the frequency bands that you specify with the Narrowband/Wideband setting on the Required Settings page of the Calibration Assistant dialog box.
Additionally, use the Exclusion Zones on the Calibration Sphere Settings dialog box to omit nulls (corresponding to areas of destructive interference) in the frequency response computation. Use calibration spheres of different sizes, or comprising of different materials to calibrate the response at nulls.
Wideband calibration settings
In addition to generic calibration settings (such as SoundSpeed), the Calibration Assistant outputs wideband-specific calibration settings, which typically have a frequency dependence.
For a full list of wideband-specific calibration settings, refer to the calibration settings for the specific wideband echosounders.
Wideband analyses
Wideband operators
These operators utilize properties in the frequency domain in wideband data:
- Code operator
- Single Target Detection - wideband
- Wideband frequency subset
- Wideband frequency select
Aside from the above list, note the many of Echoview's other operators can accept wideband variables. However, the algorithms do not perform in wideband space.
Wideband frequency response graph
Refer to the wideband frequency response graph page.