Quote Originally Posted by rnvinc View Post
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