About virtual variables

A virtual variable is created by applying an operator (a mathematical algorithm) to one or more input acoustic variables (operands). Operands may be raw variables or other virtual variables.

Operators may be chained to create additional virtual variables; that is, by using the output of one virtual variable as input to another (see example below).

When using a long chain of virtual variables, the calculations may take a significant amount of time. A progress bar is provided to indicate how quickly the calculation is proceeding. To stop the calculation, press and hold ESC while this progress bar is displayed.

You view and manage virtual variables using the Dataflow window variables and geometry tool.

To create a virtual variable:

  1. Display the Dataflow window
  2. On the Dataflow menu, point to New then click Variable
  3. On the New variable dialog box, choose the desired operator

Notes:

Example:

Shown below, is the creation of a "dB differences" virtual variable using various operators and operands.

dB difference

A description of virtual echograms is provided in the following publication:

Higginbottom, I.R., Pauly, T.J. and Heatley D.C. (2000). Virtual echograms for visualization and post-processing of multiple-frequency echosounder data. Proceedings of the Fifth European Conference on Underwater Acoustics, ECUA 2000 (Ed. M.E. Zakharia), 1497-1502.

See also

About variables
Creating and deleting virtual variables

Data types

Operators

New variable dialog box

Dataflow window

Importing virtual variables

Inheritance of properties
Calibration settings for virtual variables
Virtual variable applications
Operator licensing in Echoview
Operators that accept multibeam data