Towed body correction

Loading and viewing > Calibration > Background noise-removal > Detection and filtering > Classification > Characterization

If a transducer is mounted on a towed body, variations in the depth of the transducer during the survey will be embedded in the data. An otherwise flat bottom may appear inclined or undulating depending upon the vertical motion of the transducer while sounding. If the depth of the towed body is monitored and recorded it can be used in Echoview to correct the echogram data.

The Echoview Towed body operator (with usage caveats) may be useful for downward facing transducers mounted on a towed body.

Depth information may also be applied using the Heave source setting on the Platform Properties dialog box. This is preferable to using the Towed body operator. See also: About heave compensation.

Scenario

Towed body

Dataflow

Dataflow object	Aim	Echoview feature
Fileset1: Sv raw pings T1	Sv data from transducer on the towed body	Raw variable
Bottom line	Use recorded depth-variation data to model a line that may be used for towed body correction. Import the data as an Echoview line definition file. When logged depth-variation data is absent, use the line pick process to estimate an acoustic bottom line. Export the line to a .csv file to find the deepest depth for the line.	Editable line
Surface line	Create a Surface line based on the Bottom line. Multiply by -1 and add the value for the deepest depth variation.	Editable line
Towed body 1	Use the Surface line to correct Sv data from the towed body.	Towed body operator

Notes:

If you use the Motion correction operator and the Towed body operator, use the Motion correction first. For more information refer to Using the motion correction operator: Notes.