Looped multibeam replay with a single beam echogram

The aim of this topic is to show how you can derive a single beam echogram that can be viewed with the looped multibeam replay feature. The discussion covers one of many ways, in Echoview, to condition multibeam data for target detection. The precise method of data conditioning will depend upon the nature of your underlying data. Looped multibeam replay will also work for single beam data that has been collected concurrently with multibeam data.

Conditioning multibeam data for target detection

We use Echoview's virtual variables to condition the data then detect targets on the conditioned data. Use a Double threshold operator to remove all but the most prominent signals which are likely to be targets. Static background objects remain visible. Use a Beam closing filter 3x3 operator to remove speckles and small objects from the data, Larger static background objects remain visible. Use a Beam dilation filter 3x3 operator twice to expand the remaining objects. The intent is to merge the data that represents one target but appears as separated blocks of data in the echogram (because parts of the target were shadowed or otherwise weakly registered). This aims to prevent the detection of two or more targets where there is in reality just one. Use the Multibeam target detection operator to produce a multibeam targets echogram in which each target is represented by a colored dot. A range limit is applied in this step as well, to exclude the static background objects visible at ranges past ~10m. Use the Target conversion operator to convert the multibeam targets echogram to a single targets echogram.

Looped multibeam replay from a single beam echogram

To start looped multibeam replay

1. Display the prepared single beam echogram.
2. Display the multibeam (source) echogram.
3. On the single beam echogram draw a rectangular selection over the area of interest.
4. On the Shortcut menu (right-click), select Looped Multibeam Replay.

Notes:

• The last active multibeam echogram is used when Looped Multibeam Replay is selected.
• If you want to view a multibeam looped replay of a new selection you must select Looped Multibeam Replay again on the Shortcut menu.
• Use CTRL+D to quickly display a Looped multibeam replay of a selection.
• The displayed multibeam echogram is zoomed in to show the space representing the single beam selection. Dashed horizontal lines indicate the depth of the selection. Alternatively, dashed curved lines indicate the range of the selection. The Echogram mode on the Echogram page of the EV File Properties dialog box, affects the display of the looped multibeam replay selection boundaries on multibeam echograms. When you change the Echogram mode setting, reselect Looped Multibeam replay to refresh the multibeam display.

Looped multibeam replay functions

The looped multibeam replay time, specified by the selection on the single beam echogram, is marked by an interval on the replay time slider. Any of the replay controls can be used while the multibeam echogram is under looped replay control.

The looped replay interval also has a Shortcut menu (right-click) with the following settings:

See also

About looped multibeam replay