For reference, this is what a downscan from a Lowrance unit looks like. That’s pretty clear to interpret.
I just don’t understand the image that continues after the first return on the Garmin unit. I think the beam is narrower on Lowrance than Garmin and that what we are seeing on the Garmin is a wider beam that just joins like 7.5 degrees to either side into one acoustic image. That’s probably why you see shadows of the logs and tires in the same Downvu image in my previous post. I don’t think it is a 3D image but more of a combined one.
Dr. Depth has been unavailable for years. The designer sold his software to Lowrance and it became what is now Insight Genesis (it was one of the two). A suitable replacement is https://reefmaster.com.au/ You can only use Lowrance and Humminbird sonar data because Garmin keeps their file format closed and proprietary so there isn’t anything you can do with their data besides taking screenshots. A bit frustrating if you wanted to make sonar mosaics.