About lines

A line in Echoview is defined by a series of time/measurement co-ordinates and is displayed on an echogram by drawing line segments between adjacent co-ordinate points.

Lines are variables. They:

On echograms:

Lines can also be managed on the Dataflow window.

You can create any number of lines in an EV file.

When a new EV file is created, there is no default line. A new line must be created and made active before you can edit it or run a line pick. If a data file includes the bottom depth for a ping (for one or more variables), a sounder-detected bottom line is created for each of those variables.

All lines except sounder-detected bottom lines are available to every acoustic variable in an EV file. However, you can choose to set a line to be 'not visible' for a particular variable (on the Lines page of the Variable Properties dialog box).

The active line

An active editable line can be selected by:

Inactive lines are displayed with a width of one pixel. The active line is the line that will be edited when you choose to change the line status, or use the Line and Surface tool to edit. The active line is bulleted on the Line and Surface tool list.

At any point in time, only the active line is editable.

Notes:

Lines are described in detail in the following sections:

Line types

Editable lines

All lines other than virtual lines and raw lines are editable lines. Editable lines are displayed as solid lines. They are stored as a series of time/depth co-ordinates. Editable lines can be created, edited, deleted, and set as the active line on an echogram. You can also choose to extend editable lines during live viewing or modify sections of editable lines.

Editable lines are created in the New Editable Line dialog box or are drawn using the left mouse button.

To display a line as a graph, on the Dataflow window select a line object, right-click and select Graph.

Raw lines

Raw line data may be read from a data file. Raw lines include sounder detected bottom lines, depth lines (recorded by depth sensors) and heave lines (recorded by heave sensors). Raw lines are associated with a transducer. They cannot be edited or deleted, although they can be made 'not visible' (on the Lines page of the Variable Properties dialog box).

Sounder detected bottom lines are stored in time/range coordinates, not time/depth coordinates as other lines are. There will maximally be one such coordinate pair for each ping (all points on sounder-detected bottom lines coincide in time with pings). Sounder detected bottom lines have a Calibration page on the Line Properties dialog box which enables the conversion of range to depth.

Raw depth and raw heave lines are stored in time/depth coordinates.

You cannot edit raw lines. You can however, create new (and identical) editable lines based on the raw line, edit that line and use it in place of the raw line. The new editable line will be available to all other variables. A virtual line based on a raw line may also be useful.

Notes:

Virtual lines

Virtual lines are created in the New Virtual Line dialog box. Line operators, including those that perform line pick, are automatically listed in this dialog box.

Virtual lines cannot be edited (by the Line and Surface tool) but the formula defining them can be edited (on the Line properties dialog box).

You might for example pick a bottom line, then define a virtual line 5m above it. If you edit or re-pick the bottom line, the virtual line will be affected as well, remaining a consistent 5m above the altered bottom line.

You can change the appearance of virtual lines on the Display page of the Line properties dialog box.

Note: While you cannot edit virtual lines directly, you can create a new (and identical) editable line based on the virtual line and edit that. This new line will not be a virtual line and will not respond to changes in the virtual line dynamically.

Operators that create virtual lines are:

Line Properties

Line settings which can be viewed on the Line Properties dialog box. The line type affects the pages available under the Line Properties dialog box..

Note: The settings in the Line properties dialog box only apply when either new data is added (e.g. by live viewing) or if a section of the line is directed to be recalculated (by Shortcut menu > Recalculate Line).

To view or edit Line properties:

Calibration

Sounder-detection bottom lines use calibration settings.

Be aware that changes to calibration settings, that are used in range calculations, may shift ping data in the depth dimension but will not automatically adjust the position of existing regions and lines. You should review any existing regions and lines to ensure they are still valid.

For more information refer to Range calculation effects on regions and lines.

Color, gaps

Visibility

While creating an editable line, you can set the line to be visible for the current variable or with all variables. Subsequently, the visibility of editable and virtual lines can be set on the Lines page of the Variable Properties dialog box on a variable by variable basis. Alternatively, a line's visibility can be set on the Visibility page of Line Properties dialog box to be visible with all acoustic variables, no variables, or selected variables.

Lines depths, relative to zero meters at the water surface, are positive below the water and negative above the water. To display lines above the water adjust the Echogram display limits.

See also: Change the settings of an existing line.

Line pick

For editable lines, the line picking algorithm is configured under Single beam tab on the Lines and Surfaces page of the EV File Properties dialog box.

For virtual lines, the line picking algorithm for a Line pick operator is configured on the operator specific page of the Line Properties dialog box.

See also: Line picking.

Uses for lines

Lines are used to represent:

For example, different lines could be created to represent the depth of the sea, river or lake bed (depth of maximum backscatter), the acoustic bottom (depth of backscatter from bottom, at a defined level) and/or the second bottom (maximum return from second bottom reflection).

Echogram reference line

A line-referenced echogram displays echogram samples, regions, lines and grids relative to a specified Echogram reference line and is a display-only feature. The reference line can be any Echoview line. A line-referenced perspective may be useful during bottom line verification or while observing features in the water column.

A line-referenced echogram:

Notes:

Exclude-above and Exclude-below lines

When analyzing or integrating echogram data, lines can be selected to define the upper and lower depth limits of data points to be included in calculations. These are termed the exclude-above and exclude-below lines.

Exclude-above and Exclude-below lines are set on the Analysis page of the Variable Properties dialog box.

Export variables

You can output optional line-related variables with analysis exports. Analysis Domain variables include:

Line usage

Use Shortcut menu View Properties on the Dataflow window to display Line usage relationships (active, analysis, exclude-above and exclude-below) between variables and lines.

Grid line-reference

Cell integration and other analysis results and can be calculated relative to a Grid reference-line. Layers are numbered relative to the specified reference-line.

A editable or virtual line can be used as a reference-line for the horizontal grid of an echogram.

Note: A hidden line becomes visible when it is selected as a grid reference-line.

Export variables

You can output optional line-related variables with analysis exports. Analysis Domain variables include:

Line status

Line status can be used in a number of ways to record information or influence analyses.

The line status can be set using the Shortcut (right-click) menu on an echogram when a selection is made.

Line export

Echoview supports the export of line data under four distinct file formats.

Line-relative regions

Regions can be defined using lines to mark the upper and lower boundaries. Although referred to as "line-relative regions" in Echoview, these regions are identical to other regions. The term "line-relative" refers only to the method of creation.

Line-relative regions are used to:

A line-relative region is not dynamically linked to a line. If you edit the line(s) relative to which the region was defined you may need to redefine the region.

Find Next/Previous integram value

Use lines to constrain an integram Sv analysis. Refer to About the integram and Using the integram for more information.

Other ways to view lines

A line may viewed as a graph or in a table.

Import, Copy/Paste

Both virtual variables and line variables are included under Import Virtual Variables (.ev).

Line variables may be included in the Copy/Paste of a virtual variable chain. Lines may be discrete objects in the chain or be a selected line within the Variable Properties of another variable. For missing lines, affected settings are set to None. For unavailable lines (grey), such lines can be reconnected in the dataflow window or changed via the Variable Properties of an affected variable.

COM support

COM support for lines includes:

See also

Creating, renaming and deleting lines
Exporting line data

Importing lines

Line picking