Understanding depth sounder readings

[Brian Dinsley]

I have a Garmin 550S depth sounder. Like other sounders on the market, it gives a pictorial representation of whats on the sea bed, and in the water between the sea bed and the transponder.

As well as being able to visualise the shape of the sea bed, drop-offs etc, it shows a red band which appears to vary in thickness, presumably depending upon what the sea bed is made up of, such as sand, rock or clay??

I've looked through the owners manual, but unless I'm missing something, there isn't much to explain what it is you're looking at. What do the various colours mean?

Can anyone give some hints/ tips on how to interpret the on-screen image?

Thanks,,,,, Brian

[Poly]

brian - my understanding is the colour fishfinders generally use red to show the hardest/densest materials, then yellow then green to show progressively softer material. I am not sure the thickness of the red band will actually directly correlate to the thickness of the bottom layer - interpretation of bottom composition/structure is more art than science.

[Nos4r2]

I was pointed to this a while ago-should help a bit.

http://www.defender.com/html/fishfinder_info.html

[jyasaki]

Might try this one as well (I should probably read it as well...):

http://www.lowrance.com/en/Support/T...onar-Tutorial/


jky

[Brian Dinsley]

Thanks for the input guys,,,,, That helps a lot. I think mine's dual frequency. Look forward to trying that out now that I have some idea of what I'll be looking at.

Hope the weather stays good for the weekend so I can get to put it to the test.

Cheers,,,,, Brian