Creating and deleting virtual variables

Creating virtual variables

Use the Dataflow Toolbox or the Dataflow window to create new virtual variables, virtual lines or virtual surfaces and other dataflow objects.

Notes:

• New virtual variables by default inherit their Calibration Source. See Calibration settings for virtual variables for further information.
• New virtual variables copy some general properties from their operand(s). See Inheritance of Properties for more information.
• If you often create the same virtual variables in your EV files, you can create a template EV file with the virtual variables and their properties already defined. See About templates for more information.
• It is also possible to Import virtual variables from one EV file into another.
• If your virtual variable appears blank when viewed in an echogram window, the operand variables may not have matching pings. See Matching Pings for more information.
• You can Copy-and-Paste a virtual variable or a section of a virtual variable chain to another or same EV file.

Creating other dataflow objects

Deleting virtual variables

Complete the following steps to delete a virtual variable.

1. Click Dataflow to display the Dataflow window.
2. Click the virtual variable you wish to delete.
3. On the Dataflow menu, choose Delete

Note: Delete is not be available if the selected variable is a raw variable.

Complete the following steps to delete all virtual variables.

1. Click Dataflow to display the Dataflow window.
2. On the Dataflow menu, click Delete All Virtual Variables.
3. Note: This will also delete any unavailable virtual variables imported with a Template.

Adding new data to an existing virtual variable

Some virtual variables need to recompute the entire dataset when new data is added, i.e., they do not simply append new values.

This leads to a lag in performance while Echoview updates the results, especially when triggering operators further down the dataflow chain to recompute.

The following operators recompute their entire dataset when new data becomes available. This has performance consequences for live viewing.

• Merge pings
• Reduce Pings (Method 2)
• Region Statistic
• Sample statistic subtract
• Scan position

During live viewing

These operators, which use a centered window, recompute the entire dataset when new data is added. However, to improve performance duing Live viewing, they only reprocess existing data in the first half of the window. Downstream operators will still recompute the entire dataset.

• Attenuated Signal Removal
• Background Noise Estimation
• Background Noise Removal
• Code operator
• Cell statistic
• Match ping times
• Resample by distance
• Resample by ping
• Resample by time
• Towed body operator
• Trained model bitmap operator
• Vessel speed at pings operator
• The list of Convolution operators

See also

Dataflow window
About the Dataflow Toolbox
About virtual variables
Variable Properties dialog box
Operators
Data types
Importing virtual variables
Virtual variable applications
New Variable dialog box