Building an Artificial Reef – Tools Used in SonarWiz for Data Processing

Chesapeake Times, Vol 11 | Oct 2022

Working with our clients, I have come across many uses for the software. Recently, it was used for a project offshore Florida to build an artificial fish haven. The reef was being built with discarded concrete badge pilings, dumped in an area approximately 7 miles offshore Florida east coast.

But getting to final results took about a half dozen tools in SonarWiz, some recently updated in the
latest release of the software.

  1. Split – Auto (to take out turns) and with a mouse, for breaking a line at a specific point. In this project, a single JSF line was run, which isn’t ideal for sidescan work, as turn data will skew the data. With a few parameters for turn (length and angle), the file can easily be split into discrete segments.

2. Tool for Adjusting the data range – Unlike bathy data, overlapping sidescan data doesn’t always improve the data. In fact, when towing a sidescan, the location of the sonar isn’t exact, and the second or third pass over the same area can result in the final image being a bit blurry. The use of the Adjust display range – whether a fixed amount, or used from the variable far field, will clip the sonar data. In the fish have example, the 75meter swath was adjust down to around 50 meters, with no loss of coverage, and minimized the data overlap.

An added view for sidescan data is Coverage Map, has been updated to show the percentage coverage of the data. With the proper trimming of the data, the final coverage map will reduce the excessive overlap.

  1. Tools-CSF-Extract Water Column Data
    Build it and they will come. The fish were swimming around their newly build home. In the combined digitizer and bottom track window, we noticed points in the water column – most likely fish being caught in the signal trace. The bottom track is made to ignore these points, with a bit higher threshold, as the proper mosaic should only track the seafloor.

To view this data in 3D, we can extract the water column from the sidescan sonar. (Tools – CSF – Extract Water Column). The update in the latest release now separates the port and starboard channel into two separate XYZA files. This is the acoustic data directly below the sonar transducer. These files can be brought into a 3D display (tools – CTI 3D Viewer, Load XYZA data). With adjusting the range and color palette to match the data extent, the result will show the acoustic data from the transducer down to the seafloor.

Notice in this image, the fish appear clearly in the data display. A great tool to get another view of what is in the water column.

This fish haven continues to be built with each successive group of bridge piles added. This will be a great dive site for the Florida coast