Topic
Settings
The active line
An active line on an echogram is displayed with a width of two pixels. 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 draw tool to edit. The active line appears on the Line draw tool's drop-down list with a bullet mark.
At any point in time, only the active line is editable.
Line Properties
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 draw or pick a line. 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).
Lines themselves have properties which can be viewed on the Line Properties dialog box.
Line types
Editable lines
All lines other than virtual lines and sounder-detected bottom lines. Editable lines are displayed as solid lines. 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.
They are stored as a series of time/depth co-ordinates.
Sounder-detected bottom lines
The Sounder-detected bottom line is a special line that is the property of a particular raw variable. It cannot be edited or deleted, although it 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).
You cannot edit a sounder-detected bottom. You can however, create new (and identical) editable lines based on the sounder-detected bottom, edit that line and use it in place of the sounder-detected bottom. The new line will be available to all other variables.
Notes:
- Sounder-detected bottom lines are not affected by changes to transducer geometry in the same way that other lines are.
- Sounder-detected bottom lines that do not contain any data are defined as unavailable on the Dataflow window.
Virtual lines
Virtual lines in Echoview are lines defined relative to other lines and are displayed as dashed lines. Virtual lines change in response to changes made to the lines relative to which they are defined. They cannot be edited (by the Line draw 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.
Virtual lines are displayed as dashed lines by default. To change the appearance of virtual lines to either a dotted or solid line, use Echocolor to change the color scheme properties.
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 of course and will not respond to changes in the virtual line dynamically.
Active line
- The active line can be set by choosing a line from the drop down list on the Line draw tool or it can be set on the Lines page of the Variable Properties dialog box. If no active line is set on an echogram the Set Active line dialog box will open when you choose to change the line status or try to use the Line draw tool.
Line pick
- For editable lines, the line picking algorithm is configured on the Line Pick 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.
Line properties
To view or edit Line properties:
- for the active line, on the Echogram tools toolbar, click the Line draw tool arrow
and then click Line Properties. - select a Line on the Dataflow window then click Line Properties on the Shortcut (right-click) menu.
- for a line on an echogram under the mouse pointer, on the Shortcut (right-click) menu click Line Properties.
Line color, gaps
- Line colors are changed by altering the color scheme on the Display page of the Variable Properties dialog box. You can define custom color schemes (and line colors using Echocolor).
- You can find gaps in lines using the line-break finding tool, or make a copy of a line with all gaps bridged using the Span gaps setting on the New Editable Line dialog box.
Line visibility
- While creating an editable line, you can set the Line visibility for the current variable or of 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.
Editable lines
- Editable lines are created in the New Editable Line dialog box or are drawn using the left mouse button.
Virtual lines
Virtual lines are created in the New Virtual Line dialog box. Line operators and line pick operators are automatically listed in this dialog box.
Operators that create virtual lines are:
Uses for lines
Lines are used to represent:
- the bottom
- the lower limit of surface noise
- other linear or bathymetric features on an echogram
For example, different lines could be created to represent the depth of the sea 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).
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.
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.
Line status
Line status can be used in a number of ways to record information or influence analyses.
Line export
Two file formats are available to export line data. The .evl file format allows you to import line data in Echoview.
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:
-
create "bottom referenced layers" or analysis regions, that are a constant height above the bottom.
-
define a region to integrate the second bottom, for bottom classification studies.
-
estimate acoustic deadzone volume, by defining a region between the acoustic bottom and the depth of maximum backscatter.
Exclude-lines for analysis, Optional analysis variables and Line usage
- Exclude-above and Exclude-below lines are set on the Analysis page of the Variable Properties dialog box.
- You can output optional line-related variables with analysis exports. Analysis Domain variables include:
- Use Shortcut > View Properties on the Dataflow window to display Line usage relationships (active, analysis, exclude-above and exclude-below) between variables and lines.
Grid 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.
You can output optional line-related variables with analysis exports. Analysis Domain variables include:
- Grid_reference_line
- Layer_botttom_to_reference_line_depth, Layer_botttom_to_reference_line_range
- Layer_top_to_reference_line_depth, Layer_top_to_reference_line_range
Line status
The line status can be set using the Shortcut (right-click) menu on an echogram when a selection is made.
Line export
- Echogram menu > Export > Line
Line-relative region
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.