Sub-bottom 2 Layer Sound Velocity Model

Chesapeake Times, Vol 15 | October 2023

We are currently in the process of making some big changes in the sub-bottom sonar features in SonarWiz.  These changes implement a 2 layer sound velocity model.  Currently, the SonarWiz sub-bottom digitizer window displays data using just the sound velocity of water.  The reflectors have a multi-layer sound velocity model.  The layers are used when exporting reflectors, however they are not visualized in the digitizer window.  In order to combine the features of both we are converting SonarWiz to use a 2 layer model everywhere sub-bottom data is used.  This will move SonarWiz more towards a What You See Is What You Get (WYSIWYG) user interface.

The sound velocity model consists of 2 layers.  The first layer represents everything in the watercolumn.  This is the data that starts at the sonar and ends at the seafloor.  The second layer is everything below the seafloor.  This will more accurately represent the data visually and bring the visualized sonar data in line with the digitized reflectors.  The changes will be evident in 2 major areas.

The main update is to the sub-bottom digitizer.  Data will be displayed using 2 layers.  All reflectors, contacts, cores, etc. will be displayed taking into account the layer that they are on.  The sub-bottom digitizer in the screenshot below shows an example of the 2 layer sound velocity model.  The difference is subtle as the most visible distance is the increase of the calculated range of ~105 meters in the 2 layer model and ~100 meters in the single layer version.  The watercolumn data is the same.  The difference is all in the sediment region.  The differences increase the closer the data gets to the end of the range.

The second area that will be affected is the sound velocity for each digitized point in a reflector.   We previously had the ability to edit the sound velocity for each digitized reflector point (as shown below).  This interface is being removed.

This interface is being replaced with a simplified version that allows the user to modify the water and sediment sound velocity for each sub-bottom data file.   We are adding an Image Options tab to the sub-bottom ribbon bar that allows the user quick access to changing the sound velocity for the currently displayed data file.

SonarWiz provides a couple more ways to set the sediment sound velocity.  First, all sub-bottom files will inherit the SonarWiz default water and sediment sound velocity upon creation.   If a source sub-bottom file has sound velocity in water before it is imported, then SonarWiz will import this value.  The default sound velocities are set in the SonarWiz application advanced settings as shown in the screenshot below.

After data has been imported, the sound velocity for both the water column and sediment can be changed using the data file’s properties.

SonarWiz.  While it removes some of the more advanced capabilities, the result will be an easy to use WYSIWYG set of features that will provide solid sub-bottom data processing for SonarWiz users.