DownScan Interpretation
This explanation is to help explain what you see with down imaging, it is pertinent to all brand’s down imaging.
Down imaging has a wider cone and will show targets off the side better than the 2D sonar (traditional sonar 200 kHz).
Notice the man-made structure plus the rocks.
Sonar tells us the distance to the target. The man-made structure pointed out with the white arrow is 8 feet from the transducer. How about the red arrow? It is pointing at rocks and long strips of something man-made. You can’t tell which side it is on since the left and right edge of the cone is combined, something 12 feet from the transducer on the left with be superimposed on something 12 feet from the transducer on the right side.
If you have side scan you can see which side of the boat a target is.
Notice the rocks are opposite the man-made structure but on the DownScan they are overlapped.
The next example shows fish by a tree on DownScan and the side scan shows the same fish to the left side. The problem is we don’t have enough screens to show all we want. I like to see the map, 2D sonar, down imaging and side scan and that is a lot of dash space to be used. The fish and the tree look like white spots and are hard to interpret. I like one model with splitscreen sonar and DownScan and one splitscreen map and side scan with the side scan using 2/3 of the screen since wide screens are best for side scan like I used 2/3 for sides can in the image.
Johnnie Candle review of the Humminbird ONIX after using it last summer.
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Brief review of Lowrance CHIRP
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Another article using fish arches to help you understand sonar.
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I often get questions on what fish look like on side scan at different speeds from both Humminbird and Lowrance users.
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Learn how to interpret your Humminbird
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Learn why and how to use Insight Genesis by Doctor Sonar
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Improper Humminbird transducer placement can cause poor sonar performance.
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Review and how to use the Sonarphone T-POD.
It worked better than I predicted. If you fish from shore, docks or in a boat at anchor this is another tool for the toolbox.
