1 Target strength calibration summary

In order to calibrate the EK80, a reference target (calibration sphere) with known target strength (TS) is lowered into the sound beam. The measured target strength is compared with the known target strength of the sphere, and the EK80 is adjusted accordingly. A summary of the target strength calibration process is provided.

Prerequisites

In order to calibrate the EK80, the following equipment is required.

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Calibration spheres: The calibration spheres must be chosen to match the operational frequencies used by the EK80 system.

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Winch arrangement: The winch arrangement must provide the necessary lines to lower the sphere into the sound beam.

The vessel must be anchored in a suitable position with sufficient depth, calm and sheltered water, and minimum sea currents.

Note

Each calibration sphere must be handled with care to avoid any damage to its surface. When not in use, store the sphere in a household soap solution. All suspension lines must be as thin and clean as possible. Limit knots to a minimum, and keep them small. Even knots have strong echoes!

Kongsberg Maritime can supply a variety of copper and tungsten calibration spheres dedicated for different operational frequencies.

Procedure

Prepare the vessel for EK80 calibration.

1 Preparing the EK80 for calibration

2 Preparing the vessel for EK80 calibration

On the Operation menu, set Operation to Normal.

In the Normal Operation dialog box, set up the operating parameters for the channel you wish to calibrate.

3 Starting the target strength calibration

Lower the sphere into the beam at the specified depth. Verify that the echoes are clearly detected.

On the Operation menu, open the Record RAW button, and select On.

On the Setup menu, select Calibration.

On the first page of the wizard, select New calibration from raw data (Real time or Replay).

3 Starting the target strength calibration

Select Next to continue.

On the second page of the wizard:

Select the channel to be calibrated.

The sphere parameters can be modified in the Calibration Wizard dialog box page 3.

Select Next to continue.

3 Starting the target strength calibration

On the third page of the wizard:

Select the sphere to use in target strength calibration. You can also add a new sphere if it is not listed.

On the fourth page of the wizard:

Make the necessary preparations to record calibration data.

Select Start to start echo data import.

When the appropriate number of echoes have been imported, and the coverage plot is all green, select Stop.

Stop the recording.

Select Save or Save As to save the calibration data.

Select Next to continue.

4 Importing the echo data

On the fifth page of the wizard:

Remove the echoes you do not wish to use in the calibration.

Select Reprocess to run the calibration processing.

Select Save or Save As to save the calibration data.

Update the calibration used by the echo sounder using Merge or Replace.

5 Processing the echo data

Stop raw data recording.

Close the Calibration Wizard dialog box, and resume normal operation.

Further requirements

Repeat the procedure for each channel you wish to calibrate.