Mask

This operator applies a bitmap mask to another variable.

Data corresponding to true values in the bitmap are unchanged. Data corresponding to false values in the bitmap will be converted to the value specified on the Mask page of the Variable Properties dialog box.

Notes:

The sample at the range of a single target is used for the mask calculations. The range of the single target is distinct from the single target display thickness. Consequently, a masked single target echogram can show unmasked parts of the single target display thickness.
For complex wideband operands, no data values are set to (-999.0, -999.0). See also: The Effect of No data samples on the Wideband Frequency Response graph page.

Echoview accepts operands of the following data types as input:

Operand 1	Operand 2
Angular position Complex angular position Complex power dB Complex Sv Complex TS Linear Multibeam angular position Multibeam magnitude Multibeam phase Multibeam Sv Multibeam TS Multibeam unspecified dB Power dB Pulse compressed complex angular position Pulse compressed complex power dB Pulse compressed complex Sv Pulse compressed complex TS Single targets Sv TS Unspecified dB	Boolean Multibeam boolean

Settings

The Mask Variable Properties dialog box pages include (common) Variable Properties pages and these operator pages.

Operands page

Mask page

Setting

Description

Set masked values to

Select the value that should be assigned to samples where the bitmap is false.

-999.0 dB for dB, or 0.0 for linear (including angular position and single targets) data.
No data
Custom
Displays the setting Custom mask value to specify a number that represents false.
Notes:
- The same value is applied to both axes of the transducer beam for Angular position data types.
- No data is assigned for Complex and pulse compressed complex data types.
- See Notes above.

Mask

Settings

Operands page

Mask page

See also