Deadzone Estimation
This operator calculates estimations for the Sv values in the deadzone using techniques described in Kloser (1996). You specify the deadzone on the echogram using two lines, an acoustic bottom line and a true bottom line. Each data sample in the deadzone (the area between the lines) is replaced by the average of all values in a layer on the transducer side of the acoustic bottom line.
You select the lines and define the thickness of the layer from which the average value will be calculated on the Deadzone estimation page of the Variable Properties dialog box.
Echoview accepts a single operand of data type SV as input.
Notes:
- A deadzone estimation will not be applied to any pings in the virtual variable if either of the two lines is set to "None".
- A deadzone estimation will not be applied to specific pings in the virtual variable where:
- either line does not have a depth value at the time of the ping (e.g. at a break in either line), or
- the true bottom line for a specific ping is closer to the transducer than the acoustic bottom line for the same ping
- The thickness of the layer from which the average Sv value is calculated must be at least one sample thickness.
- If you define an exclude-below line on the resulting virtual variable you should use the true bottom line, not the acoustic bottom line, otherwise the deadzone will not be included in your subsequent analyses.
- The Deadzone estimation operator uses unprocessed data from the operand i.e. data on the operand that has been marked for exclusion or marked as bad data will be used in calculating the Sv values in the deadzone. If you want certain data to be excluded you must create a new virtual variable using the Processed data operator and then use this as the operand.
Settings
The Deadzone Estimation Variable Properties dialog box pages include (common) Variable Properties pages and these operator pages:
Operands page
Deadzone Estimation page
Settings |
Description |
Acoustic bottom |
Select the line that denotes the start of the bottom echo trace. |
True bottom |
Select the line that denotes the end of the bottom echo trace. |
Averaging layer thickness (m) |
Enter the thickness of the layer (on the transducer side of the acoustic bottom line) for which the average volume backscatter should be calculated. The calculated value will be used to fill the layer between the acoustic bottom and true bottom. |
Note: A deadzone estimation will not be applied to any pings in the virtual echogram if either the Acoustic bottom or True bottom is set to "None".
See also
About virtual variables
Operator licensing in Echoview
About the deadzone