Thread: What am I looking at?

Originally Posted by crappiepappy

I don't think it's air bubbles. I mean, why would they be coming off the bottom at an angle
Wouldn't there have to be some decent current to make the bubbles angle at ~ 45deg ?? And why in the world would bubbles split into a forked dual line ??

What intrigues me more than the angled lines, is that huge honkin' thumbnail return
That's one SERIOUSLY LARGE fish (or turtle) to put out such a large thumbnail return !!! And why didn't the unit put a large fish ID icon on that thumbnail ??

Have you tried dropping your sensitivity down a couple of notches ??
Turning off the Fish ID ??

... cp

Even tho none of the digital data shows boat speed in that shot... The boat had to be moving or the fish echo would not have created a full "arch"...

Then take into account of how an air bubble would travel up thru the cone ...as the boat moves forward ...and the pings get plotted onto the display...

The first detection of the bubble would be with the leading edge of the cone and very close to the bottom...

As the boat moves forward (and the history scrolls left)...the next ping captured the echo at a slightly shallower depth...plotting that ping data just to the right of the previous ping data ...but a minuscule higher on the display...

Repeat this over and over as the boat moves pass the air bubble...and the air bubble track would show as an angle on the display ...

Even tho the air bubble was traveling straight up toward the surface...the forward movement of the boat coupled with repetitive plotting of the air bubble data in the ping...makes the echo "Seem" to be moving at an angle thru the water column...

Rickie

Decrease your sensitivity and your colorline, try -3 on your sensitivity and about 72-75 on your colorline, and yes turn the fish symbols off

return you're seeing is soft so I would guess it to be minimal vegetation of some type, the arch is a large fish

Decrease your sensitivity and your colorline, try -3 on your sensitivity and about 72-75 on your colorline, and yes turn the fish symbols off

return you're seeing is soft so I would guess it to be minimal vegetation of some type, the arch is a large fish

Don't forget the DF shows you how far the object is from the transducer. If it happens to be right under the boat then it is also the depth, but if it was outside the cone width and came into it as you moved it would show it at the bottom and continue in a straight line until it passed out of the cone again.
For instance if you were sitting dead still in 20 FOW and a fish was swimming toward you at 10 ft. He would enter the screen at about 20 ft and continue at an angle until he swam under the boat which would show him at 10 ft.
You would see a straight line coming from 20 ft to 10 ft. (roughly)
SeaRay

Originally Posted by rnvinc

Even tho none of the digital data shows boat speed in that shot... The boat had to be moving or the fish echo would not have created a full "arch"...

Then take into account of how an air bubble would travel up thru the cone ...as the boat moves forward ...and the pings get plotted onto the display...

The first detection of the bubble would be with the leading edge of the cone and very close to the bottom...

As the boat moves forward (and the history scrolls left)...the next ping captured the echo at a slightly shallower depth...plotting that ping data just to the right of the previous ping data ...but a minuscule higher on the display...

Repeat this over and over as the boat moves pass the air bubble...and the air bubble track would show as an angle on the display ...

Even tho the air bubble was traveling straight up toward the surface...the forward movement of the boat coupled with repetitive plotting of the air bubble data in the ping...makes the echo "Seem" to be moving at an angle thru the water column...

Rickie

Yeah, Rickie --- but, if that were the case, then why wouldn't tree stumps or other vertically rising structures show on the screen the same way
I mean ... the bubbles are returning the ping, while rising vertically through the water column, just like a tree trunk would. Why would the bubbles be angled when passed over, and the tree trunk not be ?? They both would be initially picked up by the bottom leading edge of the cone, be stationary in their position, and each ping signal would be history stacked accordingly ... so why the discrepancy

Also ... why would rising bubbles create a forked split return, 2ft off the bottom point of origin ?? Even if it was bubbles, and the unit was "making" the return image look angled due to the motion of the boat ... what would account for the Y shape of the bubble column since even if you accounted for the angled image being sonar/unit related, bubbles don't act that way when rising through the water column

... cp

+1 vote for Rickie's explanation. A tree isn't moving...the bubbles are.

Rickie any ideas why the bubbles show a return? I have seen this bubble string almost every fall at this time. I think the bubbles are at an angle from boat speed,/movement.

Originally Posted by BobB

A tree isn't moving...the bubbles are.

While that may be true ... I'd think a vertical stream of bubbles would return a ping signal as a solid "object", just like the tree. And if the bubbles showed up at an angle, why wouldn't a tree show up "angled" (according to Rickies hypothesis) ??

Heck, for all we know, it could be a 12ft long Y shaped water logged tree branch ... that hasn't quite soaked up enough water to drop all the way to the bottom. (well, it could be )

That still doesn't explain the gargantuan "arch" in the image, or why the fish ID symbols are right along the angled sonar return. (and we already know that fish ID symbols are not always indicative of actual fish, since submerged trash/leaves/moss/etc can give false signals to a 2d sonar unit).

.... cp