Fish track regions can be created in Echoview by detecting fish tracks or manually creating fish track regions. Fish track regions can only be created on single target echograms.
For a region to considered a valid fish track it must:
Note: When you export fish tracks, invalid fish tracks have Num_targets equal to -1. If you use the onscreen analysis Analyze fish track, Echoview will identify the first ping with more than one target in an invalid fish track. This information is useful when you want to edit the invalid fish track, to fix it.
A single target is considered to be included in a fish track region (i.e. fall within the region) if the top most mid point of the displayed single target (rectangle) is within the region boundary.
When Echoview creates fish track regions, the boundary is defined by connecting points defined as follows with reference to the displayed single target (rectangle):
Following is a simple fish track region as created by Echoview.
A fish track by cells analysis export provides information about the number of fish tracks in each cell. For fish track analysis exports, a fish track is represented by the fish track end point. This is the right-most region point of the fish track region. A fish track is considered to be within a cell when the fish track end point is in the cell.
Given the relationship between the (fish track's) single targets and the representative fish track region, it is possible for single targets to be in one cell, while the fish track end point is in another cell. For a long fish track the targets can be in multiple cells. This kind of edge effect will be amplified if cells are very small.