3 Improving ADCP data quality with a correlation threshold value

Correlation is a measure of quality for velocities measured in the ADCP beams. High correlation indicates a low level of noise for the signals and a high quality for the velocity estimates. You can enable/disable the use of corrolation data and set a threshold value for acceptable/unacceptable correlation values.

Context

Correlation is a measure of similarity between the two sets of received echoes. The test is based on beam velocity echoes, ie. velocity along the beam direction

If the difference is small, correlation is high and the signal sequences are similar. When Correlation is enabled, velocity estimates with correlation below the threshold value are edited out. This means these velocity estimates will not be shown in the velocity views and not included in ping average. Set the correlation threshold value to remove noisy measurements for correlations values lower than the threshold value.

The correlation threshold value is managed using the ADCP Editing dialog box. The Correlation filter applies to the Beam Velocity, Vessel Velocity and Geo Velocity views. Correlation is measured in percent.

Note

This is a visual enhancement. The choice you make has no effect on the overall performance of the EK80 system.

Procedure

Open the Active menu.

Select ADCP Editing.

Select the appropriate correlation threshold value.

Enabling the threshold value will increase the quality of the data and provide more correct velocity information.

Select Apply to save your choice.

Select OK to close the dialog box.