Detecting fish tracks

Fish track detection can be carried out on a selection or on the entire single target echogram. The single target echogram can either be a raw variable or a virtual echogram.

Echoview offers the choice of two fish track detection algorithms:

The 2D algorithm uses the range and time information of the single targets.
The 4D algorithm is intended for use with split beam data and uses the angular position information of the targets in the beam in addition to the range and time.

Before you begin

Overview

The quality of the single target data affects fish track detection. See About single targets and About single target detection for more information.

The Fish tracking module outlines the features available for fish track creation and analysis.

See Fish tracking algorithms for information about the detection process and the Fish Track Detection Configuration Properties dialog box for information about the detection settings.

Narrow down to fish tracks

Consider:

Optimizing the quality of the single target data, including noise minimization, calibration, TVG, and target detection optimization.
Using exclude-above and exclude-below lines on the Analysis page of the Variable Properties dialog box, or using the Crop samples operator to remove samples according to range, depth, or sample number.
Using data thresholds on the Data page of the Variable Properties dialog box.

Note: A single target variable must contain at least two pings for fish track detection.

Caveats

Several platform properties affect fish track analysis variables.
- A mobile platform with no GPS data leads to uncertainty in angles for fish tracks.
- Fixed platforms should use Heading source: Fixed heading (north) to establish an appropriate reference frame for fish track calculations. See also: Transducer geometry illustrated.
- For a fixed platform, Water current speed source on the Position page of the Platform Properties dialog box affects fish track analysis variables that calculate horizontal speed, direction, and tortuosity. See About speed data.
- Restricted values can be reported by the fish track analysis variable Direction_vertical when the platform is moving and no position GPS fixes variable is available.
The display thickness of single targets affects fish track detection. Fish track regions are drawn around the entire display thickness of each single target. See Configuring single target display thickness.
Warning: Single targets are positioned on echograms using Target_on_axis_depth, not Target_true_depth. The depth-related calculation Fish_track_change_in_depth uses Target_true_depth when it is available; otherwise, Target_on_axis_depth is used. See About single target depths before interpreting depth-related information. The fish tracking algorithm uses neither Target_on_axis_depth nor Target_true_depth; it operates entirely in range space.

Different detections

Use different fish track detection configurations to optimize fish track detection for different data or analysis requirements.

Before running a detection, create any required region classes and fish track detection configurations. Region classes can be used to distinguish fish tracks produced by different detections.

How to detect fish tracks

To detect fish tracks in a selection of an echogram:

Bring the single target echogram into focus.
Make a selection using one of the selection tools.
On the Shortcut menu (right-click), click Detect Fish Tracks... to display the Detect Fish Tracks (Selection) dialog box.
From the Assign class list, select the region class to assign to the detected fish tracks. To create or edit region classes, click Edit Region Classes...
To delete existing fish tracks with the assigned class before running the detection, select Delete existing fish tracks with the assigned class first. For a selection, this applies to fish tracks whose final target falls within the selection.
From the Detection configuration list, select the fish track detection configuration to use.
To create or manage fish track detection configurations, click Edit Region Detection Configurations... See the Region Detection page of the EV File Properties dialog box.
To set the selected configuration as the preferred fish track detection configuration for this variable, select Set as preferred detection configuration for this variable.
Click Detect.

To detect fish tracks in the entire echogram:

Bring the single target echogram into focus.
On the Echogram menu, click Detect Fish Tracks to display the Detect Fish Tracks (Echogram) dialog box.
Complete steps 4–9 above. References to the selection in those steps apply to the entire echogram.

For information about individual configuration settings, see Algorithm, Weights, and Fish track acceptance.

Once fish track regions have been detected, it is possible to graph fish tracks, analyze single fish tracks, export fish track analyses, edit fish tracks, manually create fish tracks, and create 3D fish tracks.

Note: If you intend to apply fish tracking to a single target export file (*.target.csv) from Echoview, select Output empty single target pings on the Export page of the EV File Properties dialog box before exporting the file. Otherwise, when Echoview reads the *.target.csv file and recalculates the ping numbers, pings containing no single targets are skipped. This affects the Maximum gap between single targets and Minimum number of pings in track fish tracking settings.

Scripting support

See About region detection configurations: What changed for scripting with COM and the console? for information about COM and Command interface support.