Line Properties dialog box

The Line Properties dialog box is used to change the properties of lines, including:

changing the line name
setting line extension values for live viewing
setting line values used to recalculate a selection on an editable line
changing the formula used to define a virtual line
changing the input operands used to create the virtual line
adding notes

To display the Line Properties dialog box:

Display the Dataflow window
Display a view that includes a line
Select a Line
On the Shortcut menu (right-click), click Line Properties

- OR -

Display an Echogram
Point to a line
On the Shortcut menu (right-click), click Line Properties

- OR -

On the Echogram tools toolbar, click the Line draw tool arrow and select Active Line Properties. Properties for the active line will be displayed.

The following pages can appear on the Line Properties dialog box:

Editable line properties pages	Virtual line properties pages
Source Notes	Operands Best bottom candidate line pick Maximum Sv Line pick Fixed Depth Linear offset Off-axis angle offset Span Gaps Smoothing filter Statistical combination Crop Notes

Operands page

The Operands page is displayed on the Line Properties dialog box for virtual lines only.

Settings

Description

Operator

The operator that is being applied to create the virtual line. This cannot be changed.

Operand(s)

The line or lines that are being operated on to create the virtual line. Use the Operand list arrow to select an operand.

When available click Add New Operand to add an operand or click Remove Last Operand to remove an operand.

The large text box contains a description of the operator.

A description of the behavior of each operator can be found in the Operators section.

Notes page

The Notes page of the Line Properties dialog box is used to change the Name of a line, display the Line type of the line and add Notes.

Source page

The Source page is displayed on the Line Properties dialog box for editable lines only. The settings on the page specify line settings for live viewing and for the recalculation or repick of line sections.

The following settings are available:

Settings

Description

Line source

Displays the line source to use when:

a line is automatically extended as new data arrives during live viewing
a line is recalculated using Recalculate Line or Repick Line on the Shortcut menu.

The line source list can include:

None	Select this option to specify that you want: the line not to extend during live viewing no line to be used when creating a line or recalculating/repicking a selection
Offset from line	Select this option to create a line based on an existing line. The Offset line is specified a selection from the Offset line list. The offset settings specified are under the Offset section. It will continue to create line as new data is received during live viewing. It will apply the offset line settings for the specified selection.
Depth	This option will create a fixed depth line. The fixed depth is specified by a value entered below the Line source setting. It will continue the fixed depth line as new data is received during live viewing. It will use the value of Depth for the specified selection.
Line pick from variable	This option will pick the line using the settings on the Line Pick page of the EV File Properties dialog box. It will continue to pick the line as new data is received during live viewing. It will pick the line based on the data in the selected Variable. It will pick the line for the specified selection.

Offset

Specifies the type of line offset to apply to the Offset line.

Select one of:

Linear function

to multiply each depth and/or add (or subtract) a fixed depth from the Offset.

Off-axis angle

to apply an off-axis angle line offset to the Offset.

The Off-axis angle makes a translated copy of the existing line by calculating the equivalent depth change for a specified change in off beam axis angle. This calculation importantly assumes a vertically oriented echosounder and a flat bottom. The transducer draft only is taken from the specified transducer. See About off-axis angle line offsets for a precise definition.

General

Span gaps

Select Span gaps to span gaps in the line.

If the extension is based on a sounder-detected bottom and depth data does not arrive as expected, the extension will stop until depth data is received at which point a line segment with a line status of Unverified will connect the last received depth to the new one.

If the extension is based on another line then any gap in that line will be bridged (in the extension to this line) by a line segment with a line status of Unverified.

Otherwise, this option has no effect.

Best bottom candidate line pick page

The Best bottom candidate line pick page is displayed on the Line Properties dialog box if the Best bottom candidate line pick operator has been applied to create the selected virtual line.

This page displays the following Best bottom candidate settings:

Setting	Description
Start depth (m)	Determines at what depth (m) the Line picking algorithm will start, i.e. data above this depth will not be considered. This is particularly useful if you have high return areas at the top of your echogram that you wish to avoid being picked as bottom.
Stop depth (m)	Determines at what depth (m) the Line Picking algorithm will stop i.e. data below this depth will not be considered.
Minimum Sv for a good pick (dB)	See Best bottom candidate settings description for details.
Use Backstep	When checked the Discrimination level and Backstep range settings are available.
Discrimination level (dB)	See Best bottom candidate settings description for details.
Backstep range (m)	See Best bottom candidate settings description for details.
Peak threshold (dB)	See Best bottom candidate settings description for details.
Maximum dropouts (samples)	See Best bottom candidate settings description for details.
Window radius (samples)	See Best bottom candidate settings description for details.
Minimum peak asymmetry	See Best bottom candidate settings description for details.

See Line Pick algorithms for more details.

Maximum Sv Line Pick page

The Maximum Sv Line Pick page is displayed on the Line Properties dialog box if the Maximum Sv line pick operator has been applied to create the selected virtual line.

This page displays the Maximum Sv settings:

Setting	Description
Start depth	Determines at what depth (m) the Line picking algorithm will start, i.e. data above this depth will not be considered. This is particularly useful if you have high return areas at the top of your echogram that you wish to avoid being picked as bottom.
Stop depth	Determines at what depth (m) the Line Picking algorithm will stop i.e. data below this depth will not be considered.
Minimum Sv for good pick (dB)	This setting specifies the minimum Sv (dB) value for good line status for the Line pick algorithm.
Use Backstep	When checked the Discrimination level and Backstep range settings are available.
Discrimination level	Specifies the Discrimination level (dB) for the Maximum Sv algorithm.
Backstep range	Specifies the Backstep range (m) for the Maximum Sv algorithm.

See Line Pick algorithms for more details.

Fixed Depth page

The Fixed Depth page is displayed on the Line Properties dialog box if the Fixed depth operator has been applied to create the selected virtual line.

Setting	Description
Depth	Enter the depth, in meters, of the virtual line.

Linear Offset page

The Linear Offset page is displayed on the Line Properties dialog box if the Linear offset operator has been applied to create the selected virtual line.

Settings	Description
Multiply depth by	Enter a value to multiply the depth of the operand line by.
Then add (m)	Enter a value, in meters, to add to the resulting line.

Off-axis angle offset page

The Off-axis angle offset page is displayed on the Line Properties dialog box if the Off-axis angle offset operator has been applied to create the selected virtual line.

Settings	Description
Transducer	Select the transducer that will used in the off-axis angle offset calculation.
Angle (degrees)	Enter the angle, in degrees, that will be used to apply an off-axis offset to the input operand.

See About off-axis angle line offsets for a more detail on how the Angle and Transducer settings are used.

Span Gaps page

The Span Gaps page is displayed on the Line Properties dialog box if the Span gaps operator has been applied to create the selected virtual line.

Settings	Description
Line status	Sets the selected line status for the bridging line segments in the virtual line.

Smoothing filter page

The Smoothing filter page is displayed on the Line Properties dialog box if the Smoothing filter operator has been applied to create the selected virtual line. Smoothing is evaluated for a serially applied smoothing window.

Settings

Description

Smoothing mode

Determines the smoothing applied to the window (whose size is specified by the Number of points) for the operand line.

Select a Smoothing mode:

Maximum	Determines the maximum depth value of the sampled points in the operand line. Output line points (in the concurrent window) take on this value.
Mean	Determines the average depth value of the sampled points in the operand line. Output line points (in the concurrent window) take on this value.
Median	Determines the median depth value of the sampled points in the operand line. Output line points (in the concurrent window) take on this value.
Minimum	Determines the minimum depth value of the sampled points in the operand line. Output line points (in the concurrent window) take on this value.

Number of points (window size)

Specifies the size of the smoothing window for operand line. Enter an odd number between 1 and 49.

The applied Smoothing mode gives the depth value for the matching line points in the virtual line.

Note: A window size of 1 will create a virtual line the same as the operand line; no smoothing will occur.

Notes:

The output point will be assigned the same line status as the central input point.
If the central input point has no depth value then the output point will have no depth value.
If the window contains points with no depth value, other than the central input point, they will be not be included in the calculation.
At the start and end of the line, the window will be truncated at the boundary to the number of available points in the input line. This will result in less points being sampled on that side of the input point.
The Smoothing filter operator can only apply smoothing with respect to the time/depth co-ordinate points of the operand lines. Operand lines with few or irregularly spaced co-ordinate points may produce an unsatisfactory line (that differs from the expected line).

Statistical combination

The Statistical combination page is displayed on the Line Properties dialog box if the Statistical combination operator has been applied to create the selected virtual line.

Settings

Description

Statistic

Determines the statistical operation to apply to the operand lines (selected on the Operands page).

Select one of:

	Mean depth	The mean depth of the operand lines is output to the virtual line.
	Minimum depth	The minimum depth of the operand lines is output to the virtual line.
	Median depth	The median depth of the operand lines is output to the virtual line.
	Maximum depth	The maximum depth of the operand lines is output to the virtual line.

Divergence

Check Limit divergence to apply a divergence limit to the input depths.

Enter a value in meters for Divergence limit.

Divergence is defined as the difference of any one operand line's depth from the mean of all the operand depths, at a time T. If any operand lines have depths that exceed the Divergence limit, those lines will be ignored in the calculation of the output line at time T.

Note: The Statistical combination operator can only apply the statistic with respect to the time/depth co-ordinate points of the operand lines. Operand lines with few or irregularly spaced co-ordinate points may produce an unsatisfactory line (that differs from the expected line).

See Statistical_combination_operator algorithm for more details.

Crop

The Crop page is displayed on the Line Properties dialog box if the Crop operator has been applied to create the selected virtual line.

Settings	Description
Crop above depth (m)	Specifies the minimum depth (m) to crop the operand line.
Crop below depth (m)	Specifies the maximum depth (m) to crop the operand line.

Notes:

The virtual line will have the same number of time/depth co-ordinates as the input operand.
Line time/depth co-ordinates outside of the Crop above depth and Crop below depth are assigned a line status of None.
This operator may be useful for lines in high frequency data. See Statistical combination algorithm page: Before you begin for more information.

Line Properties dialog box

Operands page

Notes page

Source page

Best bottom candidate line pick page

Maximum Sv Line Pick page

Fixed Depth page

Linear Offset page

Off-axis angle offset page

Span Gaps page

Smoothing filter page

Statistical combination

Crop

See also