Echoview 11 sneak peek: the Calibration Assistant, a tool for calculating sphere calibration results
6 February 2020
Calibration is a critical step for hydroacoustic data processing, and Echoview 11 adds a tool to make this process easier and more transparent. Our new Calibration Assistant assists in the calculation of echosounder gain, the filter attenuation correction factor (e.g. Sa correction), and beam pattern characteristics, for any single, split, or dual beam narrowband echosounder file format supported by Echoview.
The Calibration Assistant requires:
- Narrowband echosounder data containing field measurements of a calibration sphere, ideally collected under the guidelines specified by Demer et. al (2015)
- A single target variable that contains detections of the calibration sphere
- Input of the appropriate echosounder and environmental parameters from both field and manufacturer factory measurements
- Input of the theoretical target strength (TS) of the sphere during field measurements (e.g. as calculated using NOAA AST’s standard sphere target strength calculator)
The Calibration Assistant will then calculate and report (where appropriate):
- Sa correction and transducer gain (for Simrad systems) or Sv and TS offsets (for data from other manufacturers) (dB)
- Minor and major axis angle offsets (º)
- Minor and major 3dB beam angles (º)
- Equivalent two-way beam angle, corrected for sound speed (dB re 1sr)
- RMS error (dB)
The calculated calibration settings can then easily be added to an Echoview Calibration Supplement (ECS) file to enable quantitative data analysis.
The Calibration Assistant in Echoview 11.
With the inbuilt Calibration Assistant, Echoview 11 gives you complete transparency and control over the data being used to calculate calibration parameters.
All algorithms will be fully documented in the Echoview Help file.
To complement the Calibration Assistant, three new graphs have been added to Echoview 11 that enable the visualization of uncompensated TS and compensated TS vs off axis angle, minor axis angle, and major axis angle. These graphs provide an insight into the success of beam compensation and transducer performance for data that have been collected with a calibration sphere moving across the entire beam. If calibration settings are correct and the hardware is performing as expected, then the graphs of compensated TS vs angle should be flat, while uncompensated TS values should show a dome shape associated with the beam pattern of the transducer. Haris et. al (2017) demonstrates the utility of examining calibration results using these plots.
The three new graphs are shown on the right for the calibration sphere detections plotted on the left.
The use of these features is licensed with the Echoview Essentials module.
Have you seen our previous sneak peeks for Echoview 11?
- Changing Variable Properties on multiple echograms at once
- Real-time data visualization and analysis for more file formats
- New distance mode options for single beam school detection
- Custom grid lines and labels, and improved color legends
Echoview 11 will be available for beta testing soon. Subscribe to our newsletter to be notified of the beta release, as well as other news from the Echoview team.