Explaination for this?

[schr0563]

I've seen this too. I don't buy the fish theory because the lines only appear in the ascending direction (some say this would be getting closer to the fish) but the line never descends on the back side. Seems common in 20-25 feet of water, and the lines will typically originate at the bottom and rise 15 feet or so. We often joke to "brace yourself" that whatever it is, is about to hit the bottom of the boat...

I am thinking it is some kind of electrical noise/interference issue.

[TruthWalleyes]

Disagree.

Here there are only a few fish that I truely went over top of. Those are the true arcs that you see.

The rest were on the outside of the cone, and the arc's rose in height until i went past the fish and they went out of sonar.

[bobbymalone]

your lines are a couple of feet. and they get longer the deeper you go, as expected.

I'm not seeing how that explains lines that go from 15 to 10.

the math don't make no sense

[TruthWalleyes]

There are several on my screen that are traveling 6' of depth on my screen. The Lowrance above, they're about 5-6' long as well.........

I think there is a strong correlation.

Also, with his gain obviously turned up, plus traveling at a wopping .41 mph with a screen speed set to who knows what...Yeah, i'd say its not Magic or Electrical Interference, or crab fart bubbles.

[311Hemi]

I would agree with Truthwalleye. Honestly, I didn't at first, but after more reading on the subject I believe his statements to be correct.

The reason is because you can pick up a target in the water before the target is actually in the actual transducer cone. The transducer cone, say a 20* cone only represent up to the 1/2 power point, while the usable power extends beyond that. So, for a 20* cone the actual usable power could be more around 60*. This means you can start to pick up a target well beyond what you think you would be able to, and why the ends of the target are so thin. Basically the target is starting to reach the main 20* cone zone, but not yet there. This is the same concept as why a street sign will shine at night even thought the main cone of your headlights are pointing 20-30' away.

In the OP pic, he could be picking up the fish from outside the main cone and scaring them away as he gets closer....thus why some of the lines disappear. The lines only show how far away the target is from the transducer....not the actual depth of the target. You could show a fish in 15' FOW on the screen, but it might be in 10' FOW to the left of your boat but still 15' away from the transducer.

[bobbymalone]

hmmmm, i guess i thought it was more defined to the advertised cone angle.

In the case of signals coming from outside the advertised cone angle, I'll buy it.

[311Hemi]

As did I until today. Google: Doc Samson Deciphering Sonar Charts

It will give you a lot more information on it!

[Tom7227]

K I S S

When I see these lines should I slow down or speed up to catch with the fish? Maybe I should turn right or left as they seem to be going away.

Can't sleep, but can't make sense out of the predominant explanation now either.

[TruthWalleyes]

Regular sonar "Lies" to people all the time. You really have to understand how a transducer works to be able to intrepret sonar images well. There is a ton of detail on a sonar screen - but you have to intrepret it. What's displayed is not actual.

[CaptainMusky]

Besides, I think the estimated foot error function is to allow for things like your transducer being mounted a foot below the waterline, not for correcting 10 or more feet differences between your actual depth and the depth the map shows. I have yet to see a map that shows this point correctly.

Incorrect. Keel offset I believe is the setting to adjust the transducer depth. Estimated Foot (or percentage) error IS a function of GPS accuracy. This is not going to allow you to adjust anything as in make the charting more accurate. Its telling you approximately how accurate your position is based on the GPS fix.

I am sure the issue you are seeing on your chart (no sonar) is attributed to poor mapping moreso than anything else, just wanted to point out other things that result in funky readings of the chart. My comments are solely on the chart question you had, not the sonar ones. Those questions have been accurately answered by Truth based on my experience and readings as well.

[WalleyeChaser]

The fish are always stacked under my boat!!!!

I agree with Truth on this one also. A dark arch is when the fish passed completly under the cone and the other slashes are week readings of the fish that moved to the sides before the full arch could be read.

Who the heck still uses those fish symbols from the days of Old school fish liers? Reminds me of my kids goldfish crackers!!

[TruthWalleyes]

Who the heck still uses those fish symbols from the days of Old school fish liers? Reminds me of my kids goldfish crackers!!

I think i must have done a system reset that day or something...Normally off - because them fish crackers make me hungry!

[TruthWalleyes]

Here's my buddy holding up some goldfish from the day i took that screen capture. Our first double of the day - hungry walleyes in the thermocline.

[schr0563]

So I understand where everyone is coming from. I like the sonar image Truth posted, and I agree his image shows fish. But is this really the exact same thing that Cicada is seeing (I am only considering that one thick arc that gets cut off by the side of the screen)?

Visually the two sonar images look completely different to me. Is the water depth and scale of the screen the only difference?

When I get the occasional bar that originates on the bottom in 20ft and rises to within 5 ft of the surface, the ones whose thickness (not length) is half the width of the 4 inch screen (10X the thickness of other fish arcs), are these always fish? Are there any instances of interference causing unusual sonar patterns?

[TruthWalleyes]

The origional poster's image does not look like typical interference.

Here's a shot off of a lowrance with typical intereference. Intereference is preventing the sonar from intrepreting the data at different times, so since all of our sonars are a reading displayed over time, the interference lines tend to be vertical or in some cases, horizontal.

I see no interference on the OP's image.

[TruthWalleyes]

Are there any instances of interference causing unusual sonar patterns?

Typically NO. But you can bet that almost every branch or stick shows up as fish arcs. Can't tell you how many "Non fish arcs" i used to try to catch with my old lowrance sonar. Wasn't until i switched to SI that i realized how much sonar can lie to a guy. Once you understand how they lie to you, you can better interpret the images and look for clues that give away a stick vs fish.

[schr0563]

This image answered my question. What you have shown here is exactly the type of anomally I get on my sonar from time to time (the perfectly straight 45 degree band spreading off the bottom). Clearly not a fish, definitely some kind of interference. I see your point that the original post is different. In my initial glance at his image I interpreted it the same as this interference you show here. My bad. Thanks for pointing out the difference.

[Beege]

Angled streaks = boat traveling over fish (Fish moving from outside of cone to center of cone) This is normal. Not GPS Related.

Agree

[Comit 2]

Cicada

I'm kinda freaked . I was looking at the path you were fishing. My first thoughts were you were following a weedline. Then I saw you were going from 10-30 fow. No real depth contour, just a nice tight group of trails following no real structure. What's the deal with that?????????????

I would love to see the capture at a 90foot setting. With the way some of the arks look (long on the left side and short on the right) I wonder two things, 1 is your transducer mounted right or aimed slightly ahead. 2 How much double echo are you getting.

Cold water Springs will give off that kind of reading.

This time of year with turn over there is a lot of stuff floating in the water that was on the bottom. Colder water is heaver then warm water so things that just barely sat on the bottom in the summer will suspend now. You know, the stuff that shows up in the heaver water of the thermochemical.

[jigginjim]

I would thinking many are gas bubbles, I have the same unit and see those type of lines much more in the fall. You would see the tiny bubbles on the surface as they are so small. Air bubble look bigger on the sonar screen for some reason.