Understanding Bottom with Sonar Posted on April 18, 2020

Always remember, your transducer is only showing the time it takes a signal to return and the strength of sonar return signals show the differing bottom hardness.  This palette uses yellow to show the strongest sonar returns, so harder bottoms show as yellow, then red and a soft bottom, blue.

The green arrows point to what appears to be a hard layer beneath a soft bottom. Sonar does not penetrate below the surface of the bottom. The reason the yellow is below the red is because it is showing a harder area on the edge of the cone, which takes longer for the sound to return because it is farther from the transducer than at the center of the cone.

Sonar shows how far the target is from the transducer therefore the edge of the cone is farther from the transducer.

Hard and soft bottom

You will notice the sonar “bottom” usually has the strongest return first then the next strongest after that. The diagram shows the layering of the colors. The center of the cone has the strongest signal and it weakens at the edge of the cone. Since it is weaker at the edge of the cone the returning signal at the edge of the cone is weaker and farther away so what you see is what the below diagram shows.

understanding sonar bottom

This example shows a fish over soft bottom but near hard bottom.

The green arrows point to harder bottom on the edge of the cone.

Hard and soft bottom sonar and down imaging

by Bruce Samson under

Anglers often find fish with sonar and then they don't bite, this video explains one reason they don't. Posted on January 31, 2020

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How to level your side imaging transducer Posted on December 02, 2019

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Find the fish, fish the fish and understand sonar with Aqua-Vu underwater camera Posted on November 14, 2019

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Understanding fish and trees on sonar Posted on October 13, 2019

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sonar and fish identification Posted on October 05, 2019

Using sonar, down imaging, Lowrance, Humminbird, and Aqua-Vu to study fish


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Lowrance HDS pages tip Posted on August 31, 2019

by Bruce Samson under lowrance lowrance hds

Finding Panfish in weeds Posted on July 19, 2019

Finding panfish in weeds is difficult, I will share one of my methods on this short video.

YouTube video

by Bruce Samson under Aqua-Vu lowrance sonar

Lowrance HDS LIVE product review Posted on February 11, 2019

The HDS LIVE is the latest addition to the HDS family.

This is a list of the most obvious changes

The menus and features have changed some. For example the Pages left side list has shortened and the access to Files is now called Storage.

The Side Scan/DownScan/and 3D are now all separate icons.


The 2 transducer ports are now 9 pin which now have transducer  ID so you plug it in and the software identifies the transducer so you don't have to select it. The black 9 pin hasn't changed but the blue port is still blue but has changed from 7 to 9 pin.

There is a HDMI video in to hook up to the HD Aqua-Vu cameras.


The buttons have changed, the top right button is now the waypoint button instead of the Pages button. Now I have to program my mind to quit pushing the waypoint button!

HDS LIVE buttons

Some buttons are programmable on the larger models.Watch this short video for details.


The new Active Imaging transducers produce very good side scan imaging like the 3D transducer does and makes the LIVE more affordable to get great side scan.

And coming in 2019 is the new LiveSight which will show the fish swimming on the screen!

And I bet Lowrance will add more features since that is a pattern when they release a new product!

by Bruce Samson under product reviews

Having fun using side scan sonar. Posted on January 25, 2019

I’ll introduce myself in case we’ve never met.  My name is Warren Parsons and I do many of the maps Bruce sells on his website, Doctor Sonar.  When I look to create a new map I usually research the area of interest.  A few years back, as I say “hiding out on the Texas Gulf coast for the winter” I found some interesting things in Matagorda bay around Indianola, TX. 

One day I had stopped at the Calhoun County Museum in Port Lavaca, Tx when I saw this drawing.  I put a red circle around what caught my eye.

I had been curious about something I’d see from the beach during low tide.

But this wasn’t in the right place so I checked my NOAA chart and found this where I put a red circle around.

All the NOAA chart offered me was that it called the spot an obstruction but it did link up nicely with the Indianola, Tx image . I was a little nervous as I heard that the local oyster boat had impailed itself on the smoke stake once.  So I waited for a low tide during high weather pressure, lowest water level,  to see if it showed anything and not seeing anything the next high tide low pressure, highest water level,  I ran out with my small mapping boat to this area, the small brown patch.


Turns out to have been the boiler from the steamship that caught fire and sank in 1856.

If you'd like to read more, go here:  The Perserverance




by Warren Parsons under
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