Detect 3D Schools dialog box

The Detect 3D Schools dialog box is used to enter the settings that will be used to create 3D regions.

To display the Detect 3D Schools dialog box:

  1. Display a multibeam echogram.
  2. On the Echogram menu, click Detect Schools.


The Detect 3D schools dialog box contains these pages:

Data page

The Data page of the Detect 3D schools dialog box contains the following settings:



All pings

Select to specify all pings for the detection.

Ping range

Select to specify a ping range under From and To.


Choose the Detection algorithm.

The Detection algorithms available are a function of the ping mode of the variable:


Detection algorithm

Ping mode

Cruise scanning

By ping

Instrument scanning


2 (Multibeam)





3 (H-mode)





4 (V-mode)





5 (S-mode)





Region width

Used to select the region width in meters when the By ping detection algorithm is selected.

3D Regions page

The 3D regions page of the Detect 3D schools dialog box contains the following settings:



Assign class

Select a region class to assign to the 3D regions created by school detection. Use the Edit button to define a new region class on the Classes page of the EV File Properties dialog box before a 3D school detection.

Delete 3D regions with this class first

If checked, all 3D regions in the selection/echogram that have the assigned region class will be deleted prior to detecting 3D schools.

Save vacuoles

Select this to save any detected vacuoles with each created 3D region.

Size Criteria page

The Size criteria page of the Detect 3D schools dialog box is used to control the minimum dimensions of the 3D regions and vacuoles respectively.  



Minimum longest dimension

Define the minimum dimensions (in meters) for an individual school or vacuole.

Size criteria bounding box

Any schools that are smaller than these dimensions will be discarded during the 3D school detection process.

The Minimum dimensions reflect the order of the distance between pings; this depends on the cruising speed and ping interval.  Initial values could be 30, 20 and 10 respectively. 

A 3D object's bounding box is a 3D object metric and can be displayed in a scene or the values of its dimensions and orientation can be viewed in the Further information box of the General page of the 3D Object Properties dialog box.


  • The dimensions of the bounding box are aligned with the 3D object.
  • By ping 3D school detection may not be attempted when the Region width is less that the Minimum shortest dimension values.

Minimum middle dimension

Minimum shortest dimension

Warning: 3D school detection can be very slow (taking hours on even a fast machine) and requires large amounts of RAM. This is particularly true if the minimum 3D size limits are smaller than or near to the size of individual data samples, which means that schools containing a very small number of samples will be considered during the processing. If you find that detection is slow, does not complete in a reasonable amount of time or reports running out of memory, then consider:

See also

About 3D school detection
About Scenes

Using scenes

About 3D objects

Creating 3D Objects

About Surfaces

3D Schools Detection Properties dialog box

3D object problems

Preparing instrument scanning data for school detection