How do you...well....read a graph?

[waterinthefuel]

I know it sounds like a stupid question, but I'm tired of only knowing how to find fish arches and thermoclines. I see some lines coming from the bottom at about a 70 degree angle that sometimes stick up some number of feet from the bottom......is that a tree, if so, why is it crooked? I see what looks like a giant stump, but it's big, from the bottom, to 8 feet below the surface in an area that had the stumps cut out of it in the past 20 years, is that a stump? I mean....what the hell am I seeing? I know my lake doesn't have rocky bottoms, but how can you tell bottom hardness? Automatic sensativity adjustments? Thickness of the "line" indicating the bottom? Am I on the right track?

BTW, my FF is a Garmin 240 Blue. I love it....but I'd like to know better how to use it.

 

[eurolarva]

Re: How do you...well....read a graph?

This was given to me by a fellow Iboater. It might give you better understanding on how that graph works and answer some of your questions. Open it with something like word, microsoft works.

CLICK HERE

 

[Boatist]

Re: How do you...well....read a graph?

It takes some time and practice. I think a good starting place is Lowrance SONAR TUTORIAL. It at least covers the basics.

One thing I like to due from time to time usually in the fall after most of the boat traffic is gone is to go to the clearest lake I know. Go into parts of the lake where you can see the bottom. Turn the sensitivity up until you get a lot of false returns in the area you are looking at. Now just idle around and when you find a big rock go right over it and watch the screen, see how it looked on the screen. Do the same with a bush or tree and see how they look. If your unit allows you to capture screen then capture them and print and lable what it was. You can also take a picture of the screen and do the same thing.

The thing that I have seen the most is people do not turn the sensitivity up enough. They think the screen should be clear of clutter. Well it looks better if it is clear but you will never see a fish. A fish is built like a stealth fighter and is hard to see. A fish does not have any flat surfaces to bounce the signal straight back up to the transducer. Turn the sensitivity up until you see lots of false returns in the area you are fishing. As an example your fishing 100 feet deep for bottom fish. You start turning up the sensitivity and the top of the screen is totally black so you think your good but your do not see any fish. The bottom 2/3 of the screen are clear and white until the bottom. If you want to see fish on the bottom you must keep turning the sensitivy up until your have lots of noise and clutter all the way to the bottom. Then you will see fish.

Sometime I go to a youth fishing tournment where kids are the only one allowed to fish. Adults can run the boat and net fish but not fish. Well there are a lot of cheaters where they sometimes do not even let the kids fish, so they need lots of spoter around the lake to keep it fair. I and other would help with that and after the weigh in would help anyone who was having trouble seeing fish or getting there depth finder to work. At least 90 percent of the boats you went out on had the depth finder set where the could not see JAWS. Some had the unit set to depth of 10 feet but were fishing 30 feet but most were set where they had clear screens. After the weigh in all the live bass were returned to the water. The dead fish and trout were of course not. So when your turn up the sensitivity and they start see fish they are suprised. I always turned it back down to where they had it so they could see why they never see any fish. Then let them turn it back up.

"http://www.lowrance.com/Support/Tips-and-Tutorials/Sonar-Tutorial/"

 

[jtexas]

Re: How do you...well....read a graph?

first thing to remember is, only the extreme right hand column of pixels is under you right now...everything else is history.

next, a lit pixel represents an object some where inside a circle centered directly under the 'ducer, with a diameter about 1/3 of its depth (assuming the standard 20? cone angle). that's a general rule of thumb...it could be more than 1/3 with the sensitivity turned up. other words, something showing up at 15 feet is somewhere within 2? feet of the 'ducer, but you can't tell exactly where...could be fore, aft, starboard, port or straight down, you won't know.

third, your graph will show the shallowest bottom that the 'ducer can see. So if the bottom under your boat is sloped from, say, 20 to 25 feet, you'll see the depth as 20, and fish holding at 23 feet won't show up on your graph.

sonar can't actually determine depth - just distance from the transducer. objects can appear slanted because as the boat moves closer then farther away. same reason fish appear as arches.

your stump could be some kind of vegetation, the remains of a gas well, or (in a man-made reservoir) an old homestead, chimney, vehicle. around here, people sink christmas trees, as fish habitats. works pretty good for crappie (you might know 'em as "sac a lait"). a school of baitfish under attack looks kinda like a thumbprint as they all try to crowd into the center of the school. sometimes schools of shad get so thick, the FF mistakes the school for the bottom.

geaux Tigers!

 

[dingbat]

Re: How do you...well....read a graph?

The way I was taught is if you see fish on the meter and you drop your line down and catch a trout, thems trout. See something that looks like a tree on the bottom and you drag up a branch, then its a tree.

In the end there is not quick answer. It takes a lot of time on the water with a unit to get to know what it shows on the screen and why.

Here is a real story for you:

To this day newbies to our area want to know about a "bait" that is very prevalent in our area in early spring. It has a very distinctive sonar return and at times they cover the screen from top to bottom. Yet you never see any fish around them and you never snag any no matter how thick they are under the boat..... or at least that's what they think

Funny thing, this bait leaves the area year in and year out once the water gets above 72 degrees and the salinity goes above X.X. The State even has a website that maps the movement of this "bait" around the area throughout the year.

Care to guess what this bait is?

 

[gunner1]

Re: How do you...well....read a graph?

The way I was taught is if you see fish on the meter and you drop your line down and catch a trout, thems trout. See something that looks like a tree on the bottom and you drag up a branch, then its a tree.

In the end there is not quick answer. It takes a lot of time on the water with a unit to get to know what it shows on the screen and why.

Here is a real story for you:

To this day newbies to our area want to know about a "bait" that is very prevalent in our area in early spring. It has a very distinctive sonar return and at times they cover the screen from top to bottom. Yet you never see any fish around them and you never snag any no matter how thick they are under the boat..... or at least that's what they think

Funny thing, this bait leaves the area yearin and year out once the water gets above 72 degrees and the salinity goes above X.X. The State even has a website that maps the movement of this "bait" around the area throughout the year.

Care to guess what this bait is?

Herring??

 

[jtexas]

Re: How do you...well....read a graph?

plankton?

 

[dingbat]

Re: How do you...well....read a graph?

Nope, jelly fish.

They show up as "light blue" bait on a color sounder and look like a bad case of the chicken pox on a B&W sounder. Just turn down the gain settings until they disappear.

Fortunatly you don't need a lot of gain to see a 3-4 foot long fish down 15-20' in the water column.

 

[waterinthefuel]

Re: How do you...well....read a graph?

The way I was taught is if you see fish on the meter and you drop your line down and catch a trout, thems trout. See something that looks like a tree on the bottom and you drag up a branch, then its a tree.

Now I see how you came up with your forum name!

On a more serious note....

Man I learned a whole lot with that file that I had trouble opening (none of the images worked, but the text did) and the link that was provided from Lowrance. In order to understand what you are seeing on the graph you really must understand the limitations of sonar. The fact that an object which appears slanted may simply be coming into and going out of the "cone" really helps me so much.

Thanks again. I don't know who rated this thread 4 stars, but I must agree.

 

[Boatist]

Re: How do you...well....read a graph?

As far as fish arches go it all the arches are pointed up and only get the back half of the arch then your tranducer is pointed to far back.
If they are all pointed down and only get the first half of a arch then your tranducer is pointed too far foward.

Also a narrow cone angle you will not get as big an arch as you will with a wide cone angle.

 

[dingbat]

Re: How do you...well....read a graph?

Now I see how you came up with your forum name!

Let me reiterate in non-Dingbat terminology for those with superior comprehension skills.

There is no substitute for association by first hand observation.

 

[eurolarva]

Re: How do you...well....read a graph?

If you are refering to the link I posted from my FTP site if you try and open it with word pad it should open just fine. If you use note pad it wont. I have had good luck with Microsoft word, and word pad. When the file is done down loading just right click once then select open with then choose word pad. The graphics should load just fine.

 

[jtexas]

Re: How do you...well....read a graph?

As far as fish arches go it all the arches are pointed up and only get the back half of the arch then your tranducer is pointed to far back.
If they are all pointed down and only get the first half of a arch then your tranducer is pointed too far foward.

Also a narrow cone angle you will not get as big an arch as you will with a wide cone angle.

But if some of your arches look good on the first half, but the back half is a straight line angled down, most likely those are fish that were spooked by your boat, and skedaddled about the time they got within range.