Measuring Fish Length in Catch Annotations

3.4 Measuring Length in Catch Annotation

While viewing video in FishVue Interpret Pro, you can use the length measurement tool to determine the length of individual catch items and save a record of each fish measured within the catch annotation.

FishVue Interpret Pro calculates the size of each fish by using a set of reference points marked on the measuring surface. You can measure catch displayed on video in a variety of ways; for example, fish held against a measuring board or traveling down a discard chute.

To use this tool, you must first calibrate the software by entering the measurements between each reference point on the measuring surface. This information is provided within a “Standard Measurement Report” by the technician who set up the measuring area. The length measurement tool cannot be used without this report.

3.4.1 Accessing the Length Measurement Tool

You can access the length measurement tool whenever you are creating video annotations with keypad shortcuts and field sequences that contain the length measurement field.

NOTE: Length measurement is typically part of a catch annotation record. A length measurement field must be included in the annotation in order to use the Length Measurement Tool. If you require revisions to your custom configuration package, please speak to your Archipelago Project Manager.

To access the length measurement tool:

1. Open the Annotation Shortcuts box. From the Annotations menu, select Edit Keyboard Shortcuts. Choose the full view (not the compact view).
2. In the Field Sequences section, add Length Measurement.
3. Click the button beside Length Measurement to toggle on Auto Measure.
4. Review imagery until a clear picture of the measurement grid is available. Access the catch annotation shortcut by pressing any annotation shortcut key. Tab over to the Length Measurement field and the calibration tools will appear in the video windows.

3.4.2 Calibrating the Length Measurement Tool

If the length measurement tool has not yet been calibrated for the vessel’s measurement area, you must calibrate it before you can use it. Calibration should be repeated at the beginning of each imagery review session, or if the camera setup is changed or moved in any way during the trip.

The Measurement Calibration screen features a representation of the measurement surface with an overlay of nine reference points (P1 to P9) and the spans between them. When you click a measurement field in the chute measurements section, the corresponding span is highlighted on the representation above.

The Measurement Calibration screen includes a Measurement Surface dropdown, a Calibrate button, a Test Measurement button, a Lens section, and a Chute Measurements section. The lens and chute dimension information will be provided in the “Standard Measurement Report” from the technician who installed or configured the EM system on the vessel. Calibration cannot be completed without this information.

To calibrate the length measurement tool:

1. In the camera window you want to calibrate, click the leftmost icon to display the Measurement Calibration screen. Note that you can calibrate each camera separately if required.
2. Use the Measurement Surface dropdown to select the measurement area appropriate to your review (table, conveyor belt, or discard chute).
3. In the Lens section, select the type of lens used on the vessel from the dropdown list. Complete the Chute Measurements fields using the information provided in the “Standard Measurement Report.”
4. Click the Calibrate button. The measuring grid is displayed in the camera window. Click on each of the nine reference points in order from P1 to P9 using the reference points marked on the measurement surface. When you click the last point (P9), the data is automatically saved.

NOTE: Use the forward and back arrows to skip or revisit measurement points during calibration. Use the cancel calibration button to cancel. A minimum of six points are required to calibrate the tool, and four of the first six points must be included. Using all nine points is recommended to ensure accuracy.

5. You can pan around the image when zoomed in by holding the Alt key and using the keyboard arrows.
6. Click the Test Measurements button. Click on P1 and then P2 and verify that the length is approximately the same as the length documented in L2. Repeat to test the remaining points on the grid.
7. Once finished, click the close button in the top right corner to close the window.
8. You are now ready to begin documenting catch. Use the ESC key to abort the annotation created to access the Calibration menu.

3.4.3 Using the Length Measurement Tool

While viewing a fishing event, you can use the length measurement tool to quickly measure and create a record of each fish as a catch annotation.

To measure a fish using the length measurement tool:

1. Play the video until the first fish to be measured appears fully in the frame. Click Pause to freeze the image.
2. Create a catch annotation using the annotation shortcut key. Complete the field sequence until you reach the length measurement field.
3. In the video image, left-click at the fish measurement start point, then left-click again at the measurement end point (for example, the tip of the head and the fork of the tail). A length reading is displayed in the Length Measurement field.
4. Press ENTER to accept the measurement.
5. If you do not need to enter a length measurement, press + or Tab to skip it, or press numpad ENTER to dismiss the measurement interface and commit the annotation.

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