Wideband Frequency Response Graph Properties dialog box

Wideband Frequency Response Graph Properties dialog box configures:

the variables used for frequency response calculations
the graph display settings

for the Wideband Frequency Response graph.

Notes:

The graph displays nothing when the selection is less than the Window size.
The extent of the Frequency axis is a function of the bandwidth of the transmitted pulse and a Maximum beam compensation line may not be displayed because it occurs above the bandwidth upper frequency.
Wideband frequency response graph data may be exported.
Factors that can degrade the wideband frequency response.

Variables

Use the Variables section to specify variables for frequency response calculations and specify a Reference variable for ping-time matching. The graph may be configured for one variable type. Available variables are displayed and may be selected in the Filter variable list.

The selection of a single variable from the list automatically assigns that variable as the Reference variable for calculations. However, a selection of multiple variables requires a manual specification of a Reference variable and a click on Set Reference. Be aware that in moving from the single variable case to multiple variable case, the Reference variable from the single variable case may carry over with the Set Reference button displayed as unavailable. The selection of a different variable restores the availability of Set Reference, and allows the specification of a new Reference variable.

Sv, Set Reference

The Sv variable configuration requires the specification of a Set Reference variable. This variable configuration is suited to calculating the frequency response of water column features (that are not single targets) in Sv pulse compressed wideband data.

TS, Set Reference

The TS variable configuration, (TS, Single target mask variable: None) requires the specification of a Set Reference variable. This variable configuration may result in an inaccurate TS response due to targets of interest being missed. The (TS, Single target mask variable: Single target detection - wideband variable) configuration may output a more accurate frequency response.

TS, Single target mask variable: Single target detection - wideband variable

The (TS, Single target mask variable: Single target detection - wideband variable) configuration automatically uses single target variable as the Reference variable. This configuration is suited to calculating the frequency response for target-like features in TS pulse compressed wideband data.

Apply beam compensation

The Apply beam compensation option is available for use with TS variables. See also Beam compensation.

Clear the setting to output uncompensated TS.
Select the setting to output compensated TS.

Notes:

Variables may be re-ordered in the list.
To maximize performance, the frequency response is calculated by processing some (but not all) of the pings over the selection or region. See also Wideband Frequency Response Graph Properties: Window Size.
See also Wideband Frequency Response graph: Graph calculations

Result settings

Use this section to specify custom labels, axes-limits, averaging and calculation window parameters.

Average results

Clear Average results to display individual frequency responses for each variable.

Select Average results to average the frequency responses for each variable. Average calculations are evaluated in the linear domain.

Note: no-data values in the frequency response are not included in the Average calculation.

Show minimum and maximum

Displays the minimum and maximum frequency response. This setting is available when Average results is selected.

Window size

The Window size specifies a vertical interval of samples used for frequency response calculations. Window size is used under all variable configurations.

The Window size list specifies the units for the window: Meters, Pulse Lengths, Samples.

The frequency response is calculated by evaluating samples within the selection or region. Echoview evaluates a number of Window size intervals within a ping and selected pings across the selection or region.

Notes:

The Window size cannot be less than 0.1 meters, 0.1 pulse lengths or 10 samples.
See also Wideband Frequency Response graph: Graph assumptions and calculations.

Resolution of frequency axis (kHz)

This setting allows you to specify the frequency resolution.

The frequency resolution is used to calculate the number of points for a fast Fourier transform (FFT). The number of calculated points must be as large as the selected Window size otherwise the Window size and its associated frequency resolution are used to calculate the number of points for the FFT.

NumPointsFFT = Sampling Frequency (kHz)/Resolution of frequency axis (kHz)

Where:

Sampling Frequency (kHz) is read from the data file.

Maximum acceptable time difference from reference (seconds)

This setting specifies the allowed time separation for variable pings relative to reference variable pings. Variable pings with times that exceed the acceptable reference ping time separation are not used for graph calculations. The time value can be 0.0 to 30.0 seconds.

Custom labels and Fixed limits

Refer to Graph Properties: Custom labels and Fixed limits.

Note: Wideband Frequency Response graph additional settings: Variables and Result settings sections (see above).