Inheritance of properties

A virtual variable inherits properties from its operand(s) according to the following rules:

Note: A Copy-and-Paste of a virtual variable or virtual variable chain can affect inheritance (see below).

Inheritance of calibration settings

Virtual variables inherit their Transducer and Calibration Source (SourceCal), but not LocalCal, from the first operand. Changes in SourceCal flow through to the virtual variable. Refer to Calibration for virtual variables for more information. When you want the virtual variable to use a transducer other than that of the first operand, use Override transducer inheritance on the Calibration page of the Variable Properties dialog box.


EV files created with versions earlier than Echoview 5.0 may not be entirely backwards-compatible. Pre-Echoview 5.0 virtual variable calibration inheritance support is unavailable in Echoview 5. For some data formats, the calibration settings may be different.

 In addition, the Transducer for complex (calibration) inheritance chains in pre-Echoview 5 EV files may change to conform with the Echoview 5 rule for the inheritance of properties from the first operand. The Transducer is determined from the first operand (and raw variable) at the start of the virtual chain.

Echoview defines the following calibration inheritance terminology:

Inheritance tree

A tree structure of variable operand relationships, rooted at a virtual variable of interest, which then branches through the variables operand relationships, up to the highest level of raw variables.

Inheritance chain

An inheritance chain is a flow of calibration settings from one variable to another through operand relationships.
For example, take the variable relationship:

A -> B -> C


A is a raw variable
B is a virtual variable, with A as operand 1
C is a virtual variable, with B as operand 1

Virtual variables inherit their calibration settings from their first operand. Variable C obtains its Calibration source from variable B, while variable B obtains its Calibration Source from variable A. A Local supplement can be selected for any variable, but it is not inherited.

Copy-Paste of virtual variables

When pasted, a virtual variable or variable chain is unavailable. To make the virtual(s) available, attach an operand or operands. Inheritance of the Calibration source (displayed as SourceCal on the Calibration page) is from the first operand. LocalCal is not inherited.

Borders around a virtual variable

See also

Calibration settings for virtual variables
Creating and deleting virtual variables
About virtual variables
About the Dataflow window
Virtual variable applications