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View Full Version : Getting The Most From Your Graph (Sonar, Sounder, Fishfinder Thangy, etc.)



Jerry Blake
11-01-2006, 06:11 AM
Questions on how to properly adjust graphs and decipher what they show on the screen have come up many times on this board. The following is what I have learned from using several different graphs over the years and may be something that could be made into an article for future reference. Please consider it a rough draft. I’m open to suggestions so if I’ve left anything out or not explained anything adequately please feel free to offer any suggestions that will make it more complete and concise. I’ll try to get some pictures to add in the near future. If it turns out to be helpful and worthwhile I’ll ask Ed to make it a permanent article. A lot of this is pretty basic, long and drawn out (boring) but I've tried to make it helpful for someone that has never used a graph before.

Fish Arches - What Am I Seeing?

In order to get a “fish arch” (like the manufactures lead us to believe we should be seeing on our graphs) a fish must pass completely through the “cone” or view of the transducer from one side to the other within a narrow speed range depending several variables without changing depth when either the boat passes over the fish or the fish swims under the boat.

Think of your graph screen as a composite picture of individual sonar returns. The transducer sends intermittent sound waves or “pings” down into the water and records how long it takes for each ping to return to the transducer as well as how loud that signal is when it bounces back up from the bottom or other object and returns to the transducer.

The returning sound waves are "painted" on the graph screen by filling in pixels with shades of gray or colors depending on whether you have a "Grayscale" or a color graph. The sound waves are broadcast into the water in a "cone" or circle that is narrow at the transducer and widens until it meets the bottom. Only objects that are in the cone or view can be detected by the graph.

Think of each horizontal pixel on your screen as one ping or one still photograph of what was in the view at that instant. As long as the object being painted on the screen stays in the view of the transducer the pings will continue to paint or fill in on the screen. Think of each vertical pixel as one volume setting. The louder the ping comes back the more vertical pixels it will paint and the darker or "louder" colors (on a color graph) it will paint them depicting higher volume. Higher volume means the sound wave bounced off a larger and/or harder and/or denser object.

Also, note that the display on your screen is simply a short history of what your boat passed over or what passed under your boat. The most recent information comes into view on the right side of your screen and then moves across and off your screen to the left. Depending on your boat speed and scroll speed (speed at which information passes across your screen), what your seeing on your graph isn’t necessarily under your boat and can actually be quite a ways behind you.

Arches are created because as a fish passes through the view or “cone” of the transducer it is farther from the transducer when it is at the edge of the cone and closer to the transducer when in the center of the cone. The width of the arch depends on several factors including, how fast the fish passes through the cone and also how fast your Scroll Speed is set.

The cone angle also affects fish arches because at a given speed (boat or fish) and scroll speed it takes longer for a fish to pass through a wide cone than a narrow cone at any given depth. Varying depths of fish also affects the arches because the cone gets wider as it gets deeper so the deeper a fish is the longer it takes it to pass through the cone and visa versa because of the difference in the distance across the cone at different depths.

The faster the fish passes through the cone and/or the faster your Scroll Speed is set the shorter the arch is going to be up to the point where it is just a blob instead of an arch. The slower the fish passes through the cone and/or the slower your Scroll Speed is set the longer the arch is going to be up to the point that it goes all the way across your screen.

If the fish stays in the view of the cone - either because the boat is not moving or the fish is moving at the same speed and direction as the boat – and doesn’t change depth then you’re going to see a solid line all the way across your screen instead of an arch.

If you’re sitting still or moving very slowly over a brushpile the only way you’re going to see fish arches is if a fish swims through the view of the transducer at just the right speed – probably somewhere between .5 and 3 mph depending on a variety of factors as mentioned above.

If you get over an active school of fish that is moving up and down in the water column your going to see lines that go up and down on your screen like a bunch of snakes. Crappie however are not usually that active and if you’re sitting or moving very slowly over a brushpile you can expect them to show up as solid lines on your screen rather than arches.

If a fish enters the view of the transducer and leaves in less time that it takes for that information to move across the screen but not fast enough or centered enough to make an arch then you’ll have a line on your screen that starts and stops.

To see actual sonar returns - lines or arches - and no fish symbols turn your Fish ID off. Set your overall sensitivity so the bottom shows up fairly dark (hard return) and cover – brushpiles, bamboo condos or weed beds, etc. – show up a lot lighter (soft return). Most graphs now have several different “views” – Whiteline or Grayline, Inverse, Structure ID, Bottom Black, etc., which are a variety of ways information is displayed on the screen. I have mine set to Whiteline (Humminbird) or Grayline (Lowrance), which seem to be the best for differentiating between the bottom and cover.

Continued below.

Jerry Blake
11-01-2006, 06:13 AM
How Do I Adjust My Graph For Optimum Performance?

First, make sure your transducer is pointing fairly straight down and be sure there is no oil or wax residue on the face, which could cause small air bubbles to stick to the face and interfere with the signal. Also, make sure you have a good connection where your transducer cable connects to your graph - there should be no moisture or corrosion in this connection.

I think one mistake folks make is assuming that more sensitivity means you see more on your graph, which isn’t necessarily true. Increased sensitivity simply makes everything darker (or more of the colors that depict more solid objects on a color graph) and decreased sensitivity makes everything relatively lighter (or less of the colors that depict solid objects on a color graph).

With sensitivity properly set, harder (rockier) bottom will show up darker because stronger signals are coming back to the transducer and mud or silt bottom will show up lighter because some of the signal is absorbed and less of the signal is returned to the transducer. Increased sensitivity also shows more surface clutter and electrical noise and visa versa.

You can distinguish between cover and the bottom because wood, bamboo, weeds, etc. have a different density than rock, silt or mud. Knowing what type of cover you are over, either because you put it there or have seen it when the water level was down, helps a lot in learning to identify what you’re seeing on your graph.

You can also distinguish between fish and cover because fish have a different density than wood, bamboo and weeds, etc. Probably the easiest identifying feature of a sonar return made by a fish in your “view” is that it has a constant thickness or “volume”, which shows as a consistent line across your graph. Bigger (thicker) and shallower fish will show up as thicker lines because the ping comes back louder than it does on a smaller (thinner) or deeper fish but each fish will show a consistent thickness or volume as it’s sonar return is displayed across the screen.

As the fish moves towards the edge of the cone its sonar return may be somewhat lighter or thinner because it is farther from the transducer than when it is in the center of the view but it won’t change much. Tree limbs on the other hand vary in thickness and therefore show up with an inconsistent thickness or volume. Bamboo is not very dense so it has a fairly light but consistent sonar return and shows up very similar to a school of baitfish so it’s very easy to see sonar returns (lines) made by fish that are down in bamboo cover.

When you are confident that you can distinguish between fish and cover you may want to turn your Fish ID back on and set the Fish ID sensitivity so it only shows fish symbols on some of the better fish returns. I use the Fish ID on my Matrix 12 so I can glance down and quickly see the depth of fish on the screen by the target depth shown with each fish symbol. I can still see the actual sonar returns to verify that the computer generated fish symbol is actual a fish.

My Lowrance LCX17M on the other hand is mounted on my console too far away for me to see fish symbols and their corresponding depths while I’m crappie fishing anyway so I don’t use the Fish ID on it. When I have turned on the Fish ID it filtered out all the actual fish returns and only showed the symbols, which I didn’t care for at all. It probably can be adjusted to show both symbols and actual returns like my Matrix does but I haven’t tried since I don’t use Fish ID on it anyway.

Depending on what graph you have you may or may not be able to set it to show both fish symbols/depth and actual returns. If you have to choose between one or the other you definitely want to turn off the Fish ID so you can see the actual returns.

One useful method of adjusting your overall sensitivity and your Fish ID sensitivity is to use a 1/16 to 1/8-ounce lead head jig suspended in the view of your graph. The width of the view of a 20-degree cone angle transducer is only about one-third the depth of the object your seeing so if you’re looking for your jig at a depth of 10-feet it will have to be within about a 3-foot diameter circle under your transducer. It’s easier to keep your jig in the cone if you put it down 15 or 20-feet but even then it will need to be within a 5 or 6-foot diameter circle directly under your transducer.

To adjust your overall sensitivity turn your Fish ID off and suspend a jig in the view of your transducer and slowly move it up and down a foot or two at a time. It should show up on your graph as a line that moves up and down on the screen just like you are moving the jig with a split second delay as the graph processes the information and displays it on the screen. If you have a flasher bar on the side of your screen it should show the jig moving up and down in real time.

If you don’t see your jig, slowly increase your sensitivity JUST until it starts to show up as a faint line. If your jig shows up real dark then reduce your sensitivity until it only shows as a faint line. Now your overall sensitivity should be about right but you can make minor adjustments from there if needed.

Most graphs now have an “Automatic Sensitivity” setting, which adjusts for different water conditions and depths. Even with the Automatic Sensitivity turned on you can manually set the desired sensitivity range. The Automatic Sensitivity then makes adjustments for different depths and conditions so your display is consistent. If you’re going to use your Automatic Sensitivity then be sure it is turned on before you make sensitivity adjustments.

If you are going to use your Fish ID turn it back on after you have adjusted your overall sensitivity. Now move your jig up and down as before. If you’re graph shows fish symbols along with the line depicting your jig reduce the Fish ID sensitivity until it no longer shows fish symbols. If your jig no longer shows up as a line then you may have to increase your overall sensitivity if you are going to use your Fish ID. If your jig still doesn’t show up as a line or if it only shows up with your sensitivity set so high that you can’t distinguish between cover and the bottom then you probably want to turn your Fish ID off and reduce your overall sensitivity until your jig is just a faint line again.

With even a lower end graph properly adjusted you should be able to move over a brushpile or other cover and quickly determine how deep the bottom is, how tall the cover is, whether or not it is holding fish and how deep and how close to the cover those fish are holding.

With that information you should have a good idea about how deep to start fishing and whether or not the fish are actively feeding. If you’re not marking very many fish and don’t get a bite within a few minutes knowing that you are presenting your bait at the correct depth then you can either move to another location or sit and wait for more fish to show up or the few that are there to start feeding. On the other hand if you are marking a lot of fish all up and down the water column you may have to try several different depths to determine which fish if any are actively feeding.

Taking the time to learn how to properly use your graph will save you a lot of time and help you put a lot more fish “in the box”.

stumpbumpers
11-01-2006, 06:19 AM
Man...:eek:

Jerry I really appreciate this... :)
I mean really... Thanks. :)

Your a real stand up guy...

I don't care what these other crappiers say about you:D

I will definately put this to good use and I'm sure many more will to...;)

Slab_Stalker
11-01-2006, 07:08 AM
Indeed, Thank you.
That is a help. almost nails what i asked in the other thread. YDM!

To add to this, ill share what a called a "Pearl of wisdom" in my other post.

If you decide to switch up and fish for catfish or any other scaleless fish (why would you though :) ) you can tell a catfish apart from other fish in the water with your depth finder.

To do this you will need to manually adjust your depth range for double what you are currently fishing in.

So for example let's say you are in 30 ft of water...
You will set your depth range manually from 0 - 60 ft.
Now when you look at your screen you see the actual bottom at 30 ft, and a double echo of the the bottom at 60 ft. This one will be lighter and not as defined as the one at 30.

Now lets say you have a scaled fish at 20 ft. You will see the "real" echo at 20 ft, and the double echo at 40.
Now with a catfish say at 25 ft... You will see the "real" echo at 25 ft, but there will be no double echo at 50 ft.

FWIW
-SS

anchorpuller
11-01-2006, 07:31 AM
Thank you for a very informative and useful post, Jerry. I have seen my jig on the graph at times. At other times, I wasn't able to pick it up. This gives me some insight as to how to adjust the "thangie" so I will be more able to tell exactly what I am seeing.

Mine doesn't show arches. It's a Lowrance, but probably a lower end unit. I do have fish id on it and fish alarm. I never use the fish alarm, but have put the fish id on at times. It ,sometimes, will give me an idea of how deep the fish are holding.

Right now, I mostly use it to determine depths and drop offs. I'm starting to be able to identify cover, weather it be brushpiles or rockpiles or whatever...that I've yet to learn.

With more use and messing with it, and pickin' your and other folk's brain about em, I may just be able to use one effeciently one day!

CrappiePappy
11-01-2006, 08:01 AM
Now lets say you have a scaled fish at 20 ft. You will see the "real" echo at 20 ft, and the double echo at 40.
Now with a catfish say at 25 ft... You will see the "real" echo at 25 ft, but there will be no double echo at 50 ft.

FWIW
-SS

Why is that ?? Do you know ? I was always under the impression that the depth finder was reading the air in the fish's air bladder ... and that was the "return" signal that was processed into a arch or fish symbol. Catfish have an air bladder, as does any "scaled" fish ... so, why would there be no second echo ? Fish are like us, in that they are mostly made up of water ... and the signal goes thru the body of the fish, almost as easily as it goes thru the water the fish is in. The air in the air sac is what (I believe/been told) "interrupts" the signal ... so why would it be different for a "skin" fish, over a "scaled" fish ??
I'm really interested in any substanciated info on this "pearl of wisdom". It would be great to know "how" this works !! Got any articles or web links that you can direct me to ?? ......... cp :cool:

Jerry Blake
11-01-2006, 08:28 AM
Why is that ?? Do you know ? I was always under the impression that the depth finder was reading the air in the fish's air bladder ... and that was the "return" signal that was processed into a arch or fish symbol. Catfish have an air bladder, as does any "scaled" fish ... so, why would there be no second echo ? Fish are like us, in that they are mostly made up of water ... and the signal goes thru the body of the fish, almost as easily as it goes thru the water the fish is in. The air in the air sac is what (I believe/been told) "interrupts" the signal ... so why would it be different for a "skin" fish, over a "scaled" fish ??
I'm really interested in any substanciated info on this "pearl of wisdom". It would be great to know "how" this works !! Got any articles or web links that you can direct me to ?? ......... cp :cool:

I believe what the graph picks up and displays as actual sonar returns is the sound waves bouncing off the fish’s body. Air does interrupt the sonar signal and a graph may use that information to process and display a fish symbol using the Fish ID system. But arches, as I understand it, are created by the difference in the distance from the transducer and the fish depending on where the fish is in the cone. As the fish enters the cone (or the cone begins to pass over the fish) it’s farther from the transducer, which causes it to show on the graph deeper and lighter than it does when it is in the center of the cone where it is closer to the graph, which causes it to show up shallower and thicker (louder) on the screen. As the fish passes from the center of the cone out the other side it then paints the other side of the arch for the same reason. A suspended stick or any solid object will also make an arch on your screen if you pass over it at the correct speed.

The height of the arch is relative to the width of the cone and the depth of the fish. The wider the cone and/or the deeper the fish the bigger difference there will be between the transducer and the target whether it is in the edge of the view or center. Of course the height of the arch displayed on the screen is also relative to the overall depth displayed on the screen.

I have no clue about the scaled vs. fish without scales thing. Seems like they would show up about the same relative to their size. A larger fish should show up better on a double return than a smaller fish I would think. I usually figure the fish I'm seeing right close to the bottom are walleye or catfish but I'd have to catch one to be sure.

willfish4food
11-01-2006, 08:34 AM
Thanks Jerry. It would be nice if you would post some pics of your graph and tell what you are seeing. Again thanks for the well neeed info.

ps How do you get the light to stop blinking on the vcr. Ha Just kidding!

Jerry Blake
11-01-2006, 08:35 AM
Thank you for a very informative and useful post, Jerry. I have seen my jig on the graph at times. At other times, I wasn't able to pick it up. This gives me some insight as to how to adjust the "thangie" so I will be more able to tell exactly what I am seeing.

Mine doesn't show arches. It's a Lowrance, but probably a lower end unit. I do have fish id on it and fish alarm. I never use the fish alarm, but have put the fish id on at times. It ,sometimes, will give me an idea of how deep the fish are holding.

Right now, I mostly use it to determine depths and drop offs. I'm starting to be able to identify cover, weather it be brushpiles or rockpiles or whatever...that I've yet to learn.

With more use and messing with it, and pickin' your and other folk's brain about em, I may just be able to use one effeciently one day!

Hey Laura:

Your graph will show fish arches if you have the Fish ID turned off, your overall sensitivity properly adjusted and IF a fish moves through the view of your transducer at the correct speed. BUT, I wouldn't worry a bit about arches. Learn to differentiate between the bottom, cover and fish whether the fish show up as an arch or not and you'll be good to go.

Jerry Blake
11-01-2006, 08:39 AM
Thanks Jerry. It would be nice if you would post some pics of your graph and tell what you are seeing. Again thanks for the well neeed info.

ps How do you get the light to stop blinking on the vcr. Ha Just kidding!

Hey willfish4food: (I really like that handle)

You're welcome. I'll get some pictures.

You could just unplug the VCR - and the TV - and then spend the time saved learning how to use your graph and GPS! :) But if everyone did that they wouldn't need a guide and I'd be out of work - sitting at home - watching TV. :(

willfish4food
11-01-2006, 08:51 AM
I have been fishing for years but always with a friend of mine in his boat.. I just resently Got my own boat at an auction. I will be spending the winter getting ready for late Feb. to start trolling. If you are ever in the Sardis Ms area give me a buzz and we will go fishin. NO CHARGE! I have been thinking that if I ge out there and can consistly catch fish I might try to guide some for those doctors and lawyers in Memphis. I hope I am that good someday.

speck chaser
11-01-2006, 09:14 AM
thanks jerry for the info it was very informative and i will try to adjust my lowrance this weekend thanks again

Slab_Stalker
11-01-2006, 09:32 AM
I cannot tell you how it works technically, but it does have to do with the reflectivity of the scales.
here is the original thread i saw it on.
http://www.catfish1.com/forums/archive/index.php/t-19421.html

You can also google.. catfish "double echo" and get some returns.

-SS

Matt Smith
11-01-2006, 10:06 AM
Why is that ?? Do you know ? I was always under the impression that the depth finder was reading the air in the fish's air bladder ... and that was the "return" signal that was processed into a arch or fish symbol. Catfish have an air bladder, as does any "scaled" fish ... so, why would there be no second echo ? Fish are like us, in that they are mostly made up of water ... and the signal goes thru the body of the fish, almost as easily as it goes thru the water the fish is in. The air in the air sac is what (I believe/been told) "interrupts" the signal ... so why would it be different for a "skin" fish, over a "scaled" fish ??
I'm really interested in any substanciated info on this "pearl of wisdom". It would be great to know "how" this works !! Got any articles or web links that you can direct me to ?? ......... cp :cool:

If the air pocket is what reflects back to the transducer, then why does brush and other water-logged structure show up on the sonar?

I've never heard of the air bladder producing the signal. Do you have any articles or web links to support your "impression"? :cool:

Don G
11-01-2006, 10:49 AM
We have needed a class on this for a long time...Very informative and very well described....Even I can understand....It would be nice to see some pictures especially on the Lowrance. I use Lowrance or Eagle and this would really be a help...

I think this should be saved under "Articles" or etc. for future use....

Excellent Jerry & thanks again..

Darryl Morris
11-01-2006, 11:00 AM
Here's some pics and links that offer tutorials on fishfinders and how sonar works and how the arches are created.

How Fish Arches are Made - http://www.lei-extras.com/tips/sonartut/fisharches.asp

http://www.familyfishingtrips.com/images/sonar-arch.gif
Creates the arch as the fish passes though the cone or the boat passes over and past the fish. If the boat or the fish is relatively still in the cone it will paint the return as a line running across your screen instead of an arch. Either way, once you recognize it, you'll know it's a fish.

Sonar, How it works - http://www.lei-extras.com/tips/sonartut/howitworks.asp

http://www.familyfishingtrips.com/images/sonar-howitworks.gif

Cone Angles - http://www.lei-extras.com/tips/sonartut/coneangles.asp

Sonar - Basic Operation - http://www.lei-extras.com/tips/sonartut/operation.asp

Jerry Blake
11-01-2006, 11:04 AM
Yeah, that's what I was trying to say! Took me a lot longer though. :(

bobberwatcher
11-01-2006, 11:11 AM
I hearby declare to kickstart the "Jerry Blake for President" campaign. I will hereby appoint his Vice President to be named Darryl Morris. First order of business once elected, every outdoorsman gets one week paid vacation to pursue his/her tablefare of choice.

Jerry Blake
11-01-2006, 11:20 AM
Hey Allen:

Thanks but no thanks - I just wanna go fishin! How's your youngun doing? Is she ready to go fishing yet?

DRPEPPER
11-01-2006, 11:26 AM
I hearby declare to kickstart the "Jerry Blake for President" campaign. I will hereby appoint his Vice President to be named Darryl Morris. First order of business once elected, every outdoorsman gets one week paid vacation to pursue his/her tablefare of choice.

Just spending the weekend with those two has me ready to quit and live on the bank somewhere.

Hey Jerry / Darryl
I forgot to ask you this weekend; what are your thoughts of the fish feeling the ping. I have always been in the habit of turning my electronics off after I have found my spot. I don't know if that is possible with your hovering technique. Which, by the way, works my butt off in the wind.
Don

skiptomylu
11-01-2006, 12:02 PM
Nice job Jerry! I am sure this will help lots of folks!

fishinRod
11-01-2006, 01:39 PM
Thanks a heap Jerry, like others have previously said, I truly appreciate
what you have done. For me personally you have done two things. First, some of that technical jargon in the owners manual makes a little sense now, and secondly you have confirmed what I (and my wife) have been suspicious of for years.... I really don't know what the heck I'm doing out there! LOL

crappie cowboy
11-01-2006, 02:18 PM
Jerry, I'm glad you were brave enought to write about this subject, not many
peolpe understand it at all, including me.
Now afew years ago my friend and myself did a so called test on my finder
and we were at the bank in three feet of water, holding my boat still and my
fish finder was scrolling fish and structure under the boat. I know there was no structure under the boat, I took a pole and went under the boat and found
nothing.......:eek: And I had the finder in the right mode.
And how do you set the scroll speed ?, why are the fish not swiming toward
the the boat from the front or back?, what about tree leafs floating in the water?
It made me think about when America landing on the moon and played golf,
mybe that was a hollywood set to look that way so Russian government would go broke trying to catch up in the space race, which they did...:eek:

Darryl Morris
11-01-2006, 02:21 PM
Just spending the weekend with those two has me ready to quit and live on the bank somewhere.

Hey Jerry / Darryl
I forgot to ask you this weekend; what are your thoughts of the fish feeling the ping. I have always been in the habit of turning my electronics off after I have found my spot. I don't know if that is possible with your hovering technique. Which, by the way, works my butt off in the wind.
Don

I believe it has little to no effect on the fish because of the frequency range the soundings are made. If it did I don't think we would ever catch any fish.

Barnacle Bill
11-01-2006, 03:29 PM
This thread is an excellent candidate for the Archives.

Jerry Blake
11-01-2006, 03:36 PM
Jerry, I'm glad you were brave enought to write about this subject, not many
peolpe understand it at all, including me.
Now afew years ago my friend and myself did a so called test on my finder
and we were at the bank in three feet of water, holding my boat still and my
fish finder was scrolling fish and structure under the boat. I know there was no structure under the boat, I took a pole and went under the boat and found
nothing.......:eek: And I had the finder in the right mode.
And how do you set the scroll speed ?, why are the fish not swiming toward
the the boat from the front or back?, what about tree leafs floating in the water?
It made me think about when America landing on the moon and played golf,
mybe that was a hollywood set to look that way so Russian government would go broke trying to catch up in the space race, which they did...:eek:

Graphs don't work very well in three feet of water. What you were probably seeing was surface clutter and/or electrical noise.

Not all graphs have an adjustable Scroll Speed and if they do it may be called something else. It's probably in an advanced menu and it simply changes how fast processed information is moved across and off your screen.

I'm not sure what you mean about the fish swimming towards the boat as there's no way to tell which direction a fish is swimming under the boat. All you can tell is whether or not they are in the view of the transducer.

Leaves, sticks, air bubbles and even microorganisms or anything else that a sound wave can bounce off of can show up on your graph.

Jerry Blake
11-01-2006, 03:46 PM
Just spending the weekend with those two has me ready to quit and live on the bank somewhere.

Hey Jerry / Darryl
I forgot to ask you this weekend; what are your thoughts of the fish feeling the ping. I have always been in the habit of turning my electronics off after I have found my spot. I don't know if that is possible with your hovering technique. Which, by the way, works my butt off in the wind.
Don

Hey Don:

I don't think the fish can sense the ping from a transducer and if they do they apparently don't associate it with danger. I leave both my graphs on while hovering right over a brushpile and continue using them to monitor what is going on under the boat.

Hovering in the wind can be work. First of all you need to have your boat set up properly so you're sitting comfortable facing towards the side of the boat you're fishing on and have the handle of a hand operated trolling motor within comfortable reach. Having a properly place foot switch that you can step on when needed to run the trolling motor also helps and having a heavy, low profile boat is a plus. Then it's just a matter of keeping the bow faced into the wind and using intermittent pulses from the trolling motor to keep you in position. If you do it every day you don't even think about it most of the time. You start anticipating what the wind is going to do when you feel it coming and take preemptive measures so you're not always trying to get back to the sweet spot. Now when it gets up into the 15 to 20-mph range it's time to find a protected area out of the wind.

Wiskers
11-01-2006, 04:20 PM
Thanks Jerry. Great Post! I have a Matrix 87c and Humminbird 585c & I have learned 2 things. I am running my sensitivity way too high & my scroll speed way too fast. Gonna do a little tweeking when I get back to camp tomorrow! I really believe I can "clean up" my display after reading your post!

Thanks! :D

Good Stuff
11-01-2006, 06:30 PM
Can you explain the grayscale a little more and why would tthe screen speed ever be to fast?

stumpbumpers
11-01-2006, 08:12 PM
Jerry Blake this thread may end up needing to have it's on forum with you as the moderator...:eek: :rolleyes: :p ;) :D

Jerry Blake
11-01-2006, 08:18 PM
Can you explain the grayscale a little more and why would tthe screen speed ever be to fast?

Grayscale is Lowrance's term for different shades of gray displayed on the screen to differentiate between objects by their size and density or how well they reflect the sonar signal back to the transducer. Harder and larger objects return the signal better or louder and show on the screen as darker shades of gray compared to softer or smaller objects. The LCX-17M displays up to 16 different shades of gray. Color graphs simply use different colors rather than different shades of gray to display the same information.

Grayline is another term Lowrance uses. This is from their web site:

"GRAYLINE«
This patented Lowrance feature helps you distinguish between hard and soft bottoms, where the thicker the gray band, the harder the bottom. GRAYLINE« also helps separate fish and important structures on or near the bottom from the actual bottom. Since more active-feeding fish hold close to hard bottoms and structures, GRAYLINE« helps you find more potentially productive water quickly."

Humminbird has the same type of feature and they refer to it as "Whiteline".

I guess your Scroll Speed would be too fast if it moved information off your screen before you had a chance to see it. Faster Scroll Speed is intended for faster boat speed so the graph displays what you just passed over and not what is a mile or two behind you.

Jerry Blake
11-01-2006, 08:32 PM
Jerry Blake this thread may end up needing to have it's on forum with you as the moderator...:eek: :rolleyes: :p ;) :D

Well, I have about 7-hours in it already. I was off today and needed something to do. :) I have trips scheduled for the next four days, ten trips in the next twelve-days, though so it will have to take care of itself for a while. I'll get some pictures to add and maybe that will help.

L.A. stumpjumper
11-01-2006, 08:34 PM
Thanks Jerry for this post. It is very informative.

bobberwatcher
11-01-2006, 08:39 PM
Hey Allen:

Thanks but no thanks - I just wanna go fishin! How's your youngun doing? Is she ready to go fishing yet?


Thanks for asking Jerry. She is getting better everyday. Still having trouble keeping balance and walking. Should be better in a week or two. She has been asking to go, but my two year old is ALL about counting the fish on your website. We do it every night before bedtime. Got to work this weekend, but next weekend, I may try to make a trip over to Cane Creek with them. Maybe run into LA Stumpjumper as well.

Jerry Blake
11-01-2006, 08:47 PM
Thanks for asking Jerry. She is getting better everyday. Still having trouble keeping balance and walking. Should be better in a week or two. She has been asking to go, but my two year old is ALL about counting the fish on your website. We do it every night before bedtime. Got to work this weekend, but next weekend, I may try to make a trip over to Cane Creek with them. Maybe run into LA Stumpjumper as well.

Sounds like she'll be ready to hit the water soon. I'll be back on Greeson tomorrow and hope to have plenty for your two year old to count!

CrappiePappy
11-01-2006, 11:19 PM
If the air pocket is what reflects back to the transducer, then why does brush and other water-logged structure show up on the sonar?

I've never heard of the air bladder producing the signal. Do you have any articles or web links to support your "impression"? :cool:

Second paragraph under the section "Transducer Frequency", in this article:

http://www.boatus.com/boattech/SelectTransducer.htm

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This, from a Furuno Color Depth Sounder article:

The airbladder of fish is what returns the echo to the fish finder. So the larger the fish, the larger the air bladder and thus the larger the target on your screen. Bait fish show up on the screen as a ball, because the echo is being returned on their collective air bladders. The air bladder on a single baitfish is too insignificant to return an echo, but as a school, their air bladders can be picked up by the fish finder. Remember, the denser the target the darker the color will be on your display.
************************************
This, from Pro-Troll.com article about using depth finder to selectively pick out fish species, based on their air bladder size/shape:

" Fish finders cannot read through air. Most fish have air bladders. The locator beam put out by your fish finder passes through water but cannot pass through air. Fish finders read the air bladder of a fish, and the image is bounced back to you."
*******************************************

And the Vexilar article, "How Sonar Works":
http://www.vexilar.com/help/tips/tip011.html

And, I've read other articles that basically say the same thing.
________________________________________

I've used depth finders since the first "flashers" came on the market. It has always been "reported", by these fish/depth finder mfg's, that the signal is bounced off of "anything" that's denser than water ... be that rock, weed, wood, etc. They also state that the air, in a fish's body, will interrupt the signal ... and even "warn" users to not place the transducer where "air bubbles" (caused by turbulence) will pass over it, as this will create false signals or signal clutter on your screen (and, essentially block out some of the return signals .... those of the "fish/cover/bottom").

The "ping" doesn't travel thru air very well ..... that's why you can't get a "bottom" reading, on your depth finder, when the boat is on land and the depth finder is still running. It's "sonar" ... not "radar". :D

To answer your question about why we can see "waterlogged structure" -
The "other objects" (brush, trash, thermocline, rocks, etc) are "denser" than the surrounding water ... and they reflect or absorb (change) some of the signal. That's why we get their "picture" imprinted on the screen ... the differences between the strengths of the returning signals are processed by the unit, into the pixel picture which you see on the unit.

............. cp :cool:

Jerry Blake
11-02-2006, 06:04 PM
I would think that the body parts of a fish like muscle, bone or even scales would return a signal better than air in an air bladder. If air "interrupts" the signal rather than reflecting or returning it to the transducer then it wouldn't be possible for the transducer to "see" it.

The transducer sends out a sound wave and has no way of knowing what part of that signal has been interrupted. All it can process is the small fraction of that signal that is reflected or bounced back from an object. I've dumped remains from filleted fish that no longer have any air in the air bladders over the side of the boat and they show up on the graph very much like live fish do.

When I have time to do some experimenting, I'll tie a filleted fish carcass on a line without a hook or jig and suspend it under my graph to see what it looks like.

If a graph can "see" a 1/16-ounce jig I have no doubt it will pick up bones in a fish's body.

It doesn't really matter though what part of a fish returns the signal to the transducer. What is important is having the graph adjusted so it will display fish on the screen and for the operator to understand what they are seeing on the screen.

Cane Pole
11-02-2006, 06:09 PM
" Fish finders cannot read through air. Most fish have air bladders. The locator beam put out by your fish finder passes through water but cannot pass through air. Fish finders read the air bladder of a fish, and the image is bounced back to you."
*******************************************

I believe this. Cut the air bladder out of a fish and dangle it under ur sonar. Hard to see...Fish body bout like ours. Bout 98 to 99 % water. That why higher power sonar units haver better echo return than the lower wattage units. Too much power can be bad as not enough power... catch 22 here.

Kinda sounds like some of yous guys have been sitting in on my sonar classes...ha

Cane Pole
11-02-2006, 06:22 PM
Explain this....

We know that the right screen edge is the "real time" echo return and the display is nothing more than a history file. True.
Now, with respect to the cone angle, is what we first visually see on the display: the center of the cone angle, the front of the cone angle or the rear of the cone angle?

S.S.Tupperware
11-02-2006, 06:35 PM
Good stuff,I wish all in life was that easy!!!!:rolleyes:

CrappiePappy
11-02-2006, 06:47 PM
I would think that the body parts of a fish like muscle, bone or even scales would return a signal better than air in an air bladder. If air "interrupts" the signal rather than reflecting or returning it to the transducer then it wouldn't be possible for the transducer to "see" it.

It doesn't really matter though what part of a fish returns the signal to the transducer. What is important is having the graph adjusted so it will display fish on the screen and for the operator to understand what they are seeing on the screen.

But, the word "interrupts" was MY interpretation ...... I assume that the air "reflects" a signal back. I was equating both words, to mean the same effect.
And, yes, you are quite correct ...... it doesn't really matter what reflects the signal, or why, in the greater scheme of things. I was just challenging the idea that a catfish won't show a double echo, just because it has skin (and not scales). IF the return signal is, in fact, being reflected by the air in the air bladder (as stated by most sonar mfg's) ... then why would it not show up on fish with skin, in the secondary reading, since those fish do have air bladders ?? I wasn't disputing anyones "beliefs" ... I was seriously wanting to be shown some evidence. .... cp :cool:

Jerry Blake
11-02-2006, 07:07 PM
Explain this....

We know that the right screen edge is the "real time" echo return and the display is nothing more than a history file. True.
Now, with respect to the cone angle, is what we first visually see on the display: the center of the cone angle, the front of the cone angle or the rear of the cone angle?



What you see on your display is somewhere within the view or cone but with a single beam transducer there's no way of knowing what side of the cone it is on. You can get an idea whether an object is moving from the center of the cone to the edge of the cone if the return is getting weaker as it tracks onto and across your screen and visa versa.

Humminbirds's dual beam transducer system is supposed to be able to differentiate between fish in the narrow beam or on the left or right in the wide beam.

If you're seeing fish that are 10-feet deep with a 20-degree transducer they are within about a 3-foot diameter circle so it's not too important where they are in the cone - they are right under your transducer.

When I get over a part of a brushpile that shows fish I'll throw a buoy marker just off to one side and up-wind of that area and then move the boat over and pull our baits to the area using the marker as a reference.

My Clients often ask why they don't see any fish on the graph and I explain to them that we can only see what's directly under the boat and not what's in the area we are fishing even though our bait is only 10-feet from the boat.

CrappiePappy
11-02-2006, 07:23 PM
Explain this....

We know that the right screen edge is the "real time" echo return and the display is nothing more than a history file. True.
Now, with respect to the cone angle, is what we first visually see on the display: the center of the cone angle, the front of the cone angle or the rear of the cone angle?

You know perfectly well, that a "cone" is an elongated, ever expanding circle (for lack of a better explanation) ...... a "dunce's hat" shape, if you will. Therefore, ANY display on the 2D screen is a picture of ANY intrusion into ANY part of that cone, from ANY direction, and at ANY point. The 2D screen scrolls from right to left ... and imprints the return signal, according to strength of return, as a "picture". It would depend on "direction" of the boat, if moving, as to whether you were seeing the "front edge", "back edge", or "side edge" of the cone. If boat is stationary, what comes thru the cone (from any direction) is what you "see" on the screen. The signal is reflected back from the outermost edge of influence of the cone, by anything that intrudes into the cone's "surface" ... regardless of direction.
Case in point: you're running down the lake at 10mph, flat bottom showing on the screen ... then you get a picture on-screen. Chances are, you just passed over that object. But, say the object was a really fast moving fish (going 15mph) ... coming from behind or from the side of the boat ... and it passed thru your "cone" --- it would show up the same. That's the dilemma of using a 2D unit (directional) to show a 3D cone (omnidirectional).

Ok, what grade do I get for this :confused: (hope you grade on the curve ... ha) ............ cp :cool:

anchorpuller
11-02-2006, 07:28 PM
::::gets out her lipstick:: puts up her hand:::: and offers to clean the fish for a decent grade :D

fishin3
11-02-2006, 07:46 PM
I got one for you then. I use the finder on the consul most when I am running down the lake/river. Setting the speed faster then would be a good thing right. Just slow it down when I am using it for a finder and not for depth only?

Oh by the way thanks for sheding some light on a dark subject. I think you should run for pres. You could get Darrly to be your VP. Just make sure to make crappie fishing a national job or something like that for all us fishermen/women. LOL

possumcop
11-02-2006, 08:21 PM
I don't know why people are worried about arches. I have been crappie fishin for 27 years and I am more worried about structure than arches. I fish creek channels, sudden changes in depth, stumps, brush and anything that will hold fish. This holds true for crappie and baitfish. When I see arches or screen clutter this usually means gar or stripes. Mr. Blake is right on his post. This is only complicated if you make it.

Cane Pole
11-02-2006, 08:56 PM
Glad to see everybody doing their homework here. I am suprised (and pleased) so many actually know this stuff.

By the way, the "cone angle" ain't the true picture of what is really going on. It is a simplified teaching tool so sonar is easier to comprehend.

Jerry Blake
11-02-2006, 09:05 PM
I got one for you then. I use the finder on the consul most when I am running down the lake/river. Setting the speed faster then would be a good thing right. Just slow it down when I am using it for a finder and not for depth only?



If you're just using your graph as a depth finder for running down the lake it doesn't really matter. The current depth reading is going to be the same no matter what you have your Scroll Speed or Chart Speed (the speed at which information moves across your display) set on.

If you want to see what the bottom contours are like while your cruising around - keeping an eye out for humps, channels, drop-offs, etc. - then the faster the scroll speed the better. With a slow scroll speed you may look up at your graph and see something of interest but depending on the boat speed it could be several hundred yards or even a mile or more behind you and still be showing up on the screen.

If you want to try to get your graph to show bottom contours as close as possible to how they actually are take two buoy markers and place one on the upper end of a steep slope and the other at the lower end with at least 10-feet difference in depth. Use your boat length to estimate how much distance is between each marker. Now you can determine the angle of the slope between the two markers. If the markers are 20-feet apart and at 20-foot difference in depth then you have a 45-degree slope. If they are 20-feet apart and at 10-foot different depths you have a 22.5-degree slope, etc.

Now move your boat up or down the slope past the markers at your usual fishing speed and note how the drop-off looks on your graph. If the slope shows up a lot steeper than it really is you can speed up your scroll speed and visa versa.

Of course the faster your boat is moving the steeper slopes are going to appear on your screen and the slower your boat is moving the flatter they will appear. Your scroll speed is the opposite - at a constant boat speed slopes will appear more gradual at a faster scroll speed and steeper at a slower scroll speed. There is a narrow window where you can match your boat speed, scroll speed and depth range so bottom contours will appear like they really are.

Wiskers
11-02-2006, 09:23 PM
Well Jerry I went to Ky Lake today & tweeked my Humminbirds as I said I would. WOW!!! It made all the difference in the world! I caught 26 NICE keepers & lord knows how many dinks! Turning down the sensitivity & slowing down my scroll speed really cleaned up my display. I was really over doing it! If you're ever around the north end of Ky Lake let me know. I'd like to return the favor. Thanks again.:D

P.S. I hope you don't mind but I cut & pasted your tips to WORD, and saved them on my computer.:D

Jerry Blake
11-02-2006, 10:12 PM
Hey Whiskers:

Glad it made enough sense to be useful for you. Sounds like you had a great day on the water.

Barnacle Bill
11-06-2006, 08:17 AM
Ed has added this thread to the archives in case anyone wants to go back to it easily. Excellent info!

Jerry Blake
11-06-2006, 09:25 AM
The most important thing to remember is it just takes time to learn how to use your graph for the type of fishing you do and the type of water you fish. There really are no short-cuts. I've been doing some reading on the Internet and found a lot of conflicting '"expert" opinions so you can get confused real easy.

If you can picture in your mind how a graph works by plotting sonar returns on your screen and then moving that information across and off the other side of your screen you can learn to recognize what is on your screen.

If you'll take the time to experiment with different setting and options looking at different known objects under the water it will be well worth it. For example: Take a dead fish that is still intact with it’s air bladder in place and see how it looks at 10 and 20-feet deep under your transducer. Take a fish carcass and suspend it below your transducer and see how it compares to a whole fish. Take a live fish and let it swim around under your boat and see what it looks like. Tie fishing line directly to each of these so you know your not picking up any terminal tackle. If you can’t see any sonar returns depicting fish under your boat doing any of these experiments then adjust your graph until you do.

Yesterday, I dumped a tub full of fish remains over the front of my boat as it was slowly moving forward and they showed up real well – first as a tight bunch similar to a school of bait fish – even got a few fish symbols around the top edge. Then as the fish scraps separated as they sank towards the bottom the wad on the graph spread out and got deeper until it went out of the view of the transducer. There weren’t any air bladders in any of the fish remains so this experiment again confirmed to me that my graph, set the way I use it, doesn’t necessarily detect fish by their air bladders.

Yesterday, I had a kid jigging a ╝-ounce spoon while sitting near the front of my boat over the transducer. When he would ask me if he was fishing deep enough I would move the boat towards the side he was fishing on, which moved the boat (and transducer) over the spoon so my graph could pick it up. We could then see his spoon showing up on the graph like an electrocardiogram and I could tell him how deep his spoon was at the top and the bottom of each stroke.

He caught five real good crappie jigging that spoon (and several others on minnows) and you can tell by the look on his face how much he enjoyed it. He’s on the left in this picture:


http://www.actionfishingtrips.com/11-5-06.JPG

It's hard to get good digital pictures of my graph because of the reflection from the screen but I'll work on that when I have time.

Gamblinman
11-06-2006, 06:57 PM
It's hard to get good digital pictures of my graph because of the reflection from the screen but I'll work on that when I have time.
I've never understood why Lowrance will not use the anti-reflective glass like they use for photographs and posters that hang on the wall in their units. I've asked them many times without a answer.

Jerry, you can get an anti-reflective coating on a clear plastic sheet that sticks to unit. It helps tremendously with viewing in sunlight and dimming any reflections. Just trim it to size, lay it on and sqeegee out any air pockets. It protects the glass from scratches. I usually replace mine once a year.

Jerry Blake
11-06-2006, 07:16 PM
I've never understood why Lowrance will not use the anti-reflective glass like they use for photographs and posters that hang on the wall in their units. I've asked them many times without a answer.

Jerry, you can get an anti-reflective coating on a clear plastic sheet that sticks to unit. It helps tremendously with viewing in sunlight and dimming any reflections. Just trim it to size, lay it on and sqeegee out any air pockets. It protects the glass from scratches. I usually replace mine once a year.

Hey Gamblinman:

That's and excellent idea! Where do you get the stuff? It would be great to kill the glare and even better to protect the lens. I need it on my GPS as well because the lens on it gets scratched up too.