Leanin post,
I forgot to mention course up. thanks

alot of people also dont ever think abt setting thier 83 khz sensitivity adjustment. I t is a seperate adjustment, that when adjusted right will make the brushpiles look alot larger, and more detailed on the screen, as you go over them. Most people including myself find brush by splitting the navigation page and 2d page. with the nav page being the active page. then zoom the map in and out as needed. So what you do is go to your 2 d only page and from there go to the menu, and set both beams to on, 83/200.
Then find the 83 khz only adjustment, this is your 60 degree cone, the widest one, the less detailed but more coversge beam. Set it to around 4 or 5 to start. Then go over a brushpile. You should see ALOT more of the pile instead of a sparse little teepee.

you need to look at your humminbird sonar, as 4 seperate systems, built into one. with 2 sub systems. The 2 sub systems are the 2 deminsional sonar, and side imaging sonar. Each subsystem breaks down into 2 more systems, The 2d sonar breaks into eithr 83 or 200 khz.. And the side imaging breaks down into either 455 or 800 khz.
As you are setting up your unit ,you need to keep in mind what exactly is happening with the systems. YOU MUST KNOW EXACTLY HOW YOUR UNIT OPERATES, BEFORE YOU CAN ADJUST IT PROPERLY.
Start of adjusting your 2 subsystem, and keep working with it until you understand how changes in settings affect it. Then go to your side imaging subsystem and learn how those work. You will soon realize that adjusting one subsystem, affects the other, so achieving a balance, that is effective, then becomes the goal. It sounds complicated but its really not. you just have to spend time with the unit, and explore it, and dont be afraid to see what it can do.

leanin post;
your last 2 posts were a big help to me

thanks

Also I like to use my fish ID feature. dont believe the old falsity that the fish symbols are for beginners. Anyone with any common sense will realize that when you fish cover such as brushpile,s . if you have your unit set to arches only, the arches will disappear in the brush, FISH ID gives you arches AND FISH symbols. and the great thing is that the fish symbols will be 2 different colors according to which sonar beam is picking the fish up. either the 200/ or 83.(make sure your unit is set so both beams are on. ) This is a great advantage because it tell you if you are getting closer to the fish are farther away,. Lets say for example you were trying to stay on a school of white or black bass, or hybrid, that were following shad. If you know that the narrow beam shows fish symbols in orange, and the wide beam shows them in blue, then you can tell where the largest concentration of fish are, directly underneath the boat by how many and what color fish symbols are showing,.
Second big advantage of using symbols is its alot easier to size the fish,. Typically the medium to small sized symbols will be crappie and small white bass. medium to large symbols will usually be white bass, black bass, and hybrids.
Your fish id sensitivity setting is also important. I have found, that with the fish id sens set to 5, it eliminates the unit from picking up large shad, perch, and other small fish as a small symbol. I learned this after fishing a large school of izzard shad, then setting my unit to just tune them out. Also if you are fishing around bridge piling,s and not seeing anything on your sonar, or hearing any beeping, they arent there., (I like to set my audible fish alert to high tone).
If you pull up to a brushpile, and start seeing fish symbols, and it starts beeping, there usually crappie there. If you see a bunch of medium sized fish symbols, its small crappie. if a lot of medium sized symbols, and a few small oones its likely big crappie. If all or most large size, the its likley large white bass, gar, catfish, bass , ect. especially if theres alot of shad around the area.
USE THE FISH ID FEATURE!!! It gives you alot more information.

something else that is very important on your trolling motor transducer, when fishing timber or especially bridge piling,s is how deep in the water your trolling motor head is. Keep in mind the transducer is either built into or mounted in the bottom of the trolling motor. The sonar beam shoot in a downward cone, all the way to 180 degrees to the side if you have a side imaging transducer, but the beam never shoots upward. So if you are trying to scan bridge pilings in 10 feet of water, and you have your trolling motor head unit 3 to 4 feet below the water line, thats not giving to transducer much of an angle to see much of the piling. So try to keep the trolling motor in the water just deep enough to prevent cavitation, so you get the broadest coverage from your transducer. If you have a 20 degree cone transducer, check with your manufacturer, many offer a 60 degree of coverage transducer, that can make a huge difference in what you see. Before I got side imaging, I had 2 fishmark 480 units, with a 60 degrees transducer mounted on each side of my transom, the way I mounted them the beams overlapped a bit. In 20 feet of water, it gave me close to 30 feet of coverage. So I mounted the head units side by side, looking at them both. I could make one pass down a probably area, and usually find brushpiles the first pass. I found piles with that set up that people were missing with side imaging units because it was always an overhead view, where as sideimaging shoots a very narrow slice, and sometimes the objects look very sparce, depending on the angle, speed, list of the vessel, distance, ect.

As far as fish symbols:
Do the units properly show fish ID's while you are sitting still over a brushpile?
I would believe the id's are coming from processing in the unit that find's distinct returns, aka arches, therefore you must be moving at some speed over it. Just wondering if that is true or not.

several different things must occur, before the unit will throw up a fish ID signal Humminbird put alot of technology into this feature. It is usually quite accurate. Any sonar can be fooled though. I have alot of confidence in the feature. also its almost impossible to sit completely still over a brushpile, and very slight movement is all thats needed. ONCE AGAIN. that is where the DUAL BEAM feature comes into play,. a wide cone is overlapping a narrow cone. If a fish is moving around you will see different color fish Id symbols as the go from directly under the tranducer, to up to 60 degrees away,. I f you are sitting still a an orage fish symbols shows up on sonar, then a blue one at the same depth, its likely a fish just swam past your transducer.

Thanks for the response. I guess im more after understanding the actual technology. Such as gates and signatures, encoding, or whatever it is to distinguish a branch from a fish if your sitting relatively still. I was always under the impression the symbols came from processing arches, but if your relatively still, everything is a flat line unless it's swimming in and out of the beam. Thanks for all the great posts. I enjoy them and they do help.

I guess the summation is that an experienced fisherman knows it works someway, somehow. That's part of what I was after and will give me more confidence. But mow my curious mind wants to know how!

because not only does the sonar detect the hard density of the fishes bones, it picks up the air bubble in the fishes air bladder. So it dont matter if the fish, or the boat is moving as much when using these things. diferent size fish have different size air bladder, not all big fish have big air bladders but for the most part that is the case.
As far as the program and exact technology, that is proprietary and wont be given up by the engineers.
One night I was tied up in a cove, and ALOT of basitfish and gamefish were coming in,. I was looking at split screen 2D, and side imaging. Well I saw what looked like a branch floating by under my boat, but it wasnt, it was the orientation of fish, and baitfish, that fooled the processor, into throwing a branch up on the screen., So this tells me that it is a computer generated image, and not like an actual photograph.

On large saltwater graphs, the fish arch will look like a different colored. teardrop, within the arch of the fish, this is the bloodline of oxygen and iron that is inside of the fish, and has a different density then the outer part of the fish. On smaller freshwater fish, we dont see all off that, they dont have 3 gallons of blood in them.

Think of it this way. if you took a balloon filled with air, and tie it to a string and tied it to a rock and sunk it a foot off the lake bottom in 20 feet of water,]. Then you pulled on top of it with your boat, and turned your sonar on. Everytime your sonar sends out a ping, your unit will put a fish symbol on the screen, the boat not moving, the balloon is not moving, but you will get a fish symbol. Does that clear things up?

If you drove over an underwater spring that was bubbling like crazy, you would think you hit the motherload because it would show as fish symbols or arches..
Sometimes you can find white bass that are hugging the bottom really tight, by spotting the tiny air bubble in thier bladder, inside of the arch. the arches will look like a rock pile on the bottom, or just some curvature, but the tiny round dot, can give them away.

Not trying to keep beating the unfortunate horse.. Im just trting to learn a bit more to understand how i can use the unit better. I guess the confusion is how the unit understands the difference between a balloon of air and let's say the top of a stump or tip of 2" branch or sticking up from the bottom, like what the unit may see sitting on top of a brush pile. They both return the signal on every ping. Would they both give a fish symbol. That's my question. I think you answered it saying its their secret. And I guess I may need to turn that feature back on and play more. Btw- you do a great job at teaching and explaining. My favorite thread.

Its all an educated guess for the most part, based on whats in the lake. The speed at which the sonar ping returns, is dependent on the density of the object,. The density of a fish, and the fact it has a air bladder, likely fall into a certain " slot". Once it falls into this slot, the processor then tries to break it down even further, into which size slot.
Side imaging unit get more information because there are 4 individual crystals firing at the same time, in one transducer.
The more information the higher the propability of accuracy.
Also the faster the crystals fire (ping speed), the more information.
Recently there was a pic posted of someone who had just dropped a pvc condo and he went over it with his downscan. It showed as a fish on every tip of the pvc condo. Surely it was not fish, because he had just dropped the condo. What it was was either air bubbles trapped in the bent ends of the top of the pvc, or a density difference in the ends, like a fitting glued onto the end of the pvc. So you must keep in mind, these sonar units cannot think and reason , they process info. The sonar didn't know that it was a pvc condo, it just measured the density of the object, and gave its best assessment.