Let’s talk about SONAR ECHO STRENGTH.

This is how your 2D CHIRP sonar creates a picture for you and this is how Active Imaging Structure Scan DownScan creates a picture for you. What they do, is that they display Echo Strength (ES). ES means the strength of the sound that comes back to the transducer after it hits the target. The target could be a fish or the bottom. So, on the left side you see these little dots, little blue/red arches and you see that one big one! It is showing the different size of the fish based on echo ES. The color of the fish/arch is red with orange and it’s thick!

On the right side, the Active Imaging DownScan SIMRAD FishReveal smart target viewing shows that it’s a yellow thick stripe, parallel to the bottom. The yellow stripe is ES: brighter and thicker yellow is stronger and darker yellow thinner arches are weaker! On the other side, orange is the brightest (it’s the strongest ES), red the second and then blue! The color that represents the bottom is brown. The hard limey bοttom on the Active Imaging DownScan is like a bright grey (strongest ES) while the sand is like a white.

All of this is telling you how much sound is coming back and finally creates that whole picture for you!

If you want to understand how the sonar works, go to

Vassilis is a passionate and knowledgable freediving and spearfishing trainer.

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