J-Doc Posted July 11, 2013 Share Posted July 11, 2013 SONAR INTERPRETATION - HOW TO READ MY SONAR (FISH FINDER) AND UNDERSTAND WHAT I’M LOOKING ATI'm starting this thread in hopes that it will become a "sticky" at the top of this forum. I hope this thread serves the novice sonar user and the experienced sonar user as well. First a few questions: How many of us have a fish finder? (I'm guessing 90% of us do) How many use the "fish symbols" because without that, you just don't know what you're looking at and don't have enough confidence in your graph to find fish without it? Do you turn the sensitivity down so much that it will only show "big fish" or big solid objects? Do you know what you're looking at??? (hey, I have to ask) :-) Well....... This is where I hope the "experienced" angler can teach the "inexperienced" sonar user. Where the super-sharp guys that have the really expensive equipment and vast experience can teach some of the common weekend anglers that may only have the $100 Lowrance Cuda, the $70 Humminbird, or some older fish finder their buddy gave them that’s so old, you can’t even find it on the internet. If it will show fish arches, then you can learn something here.What am I seeing on my graph?Is that a bass or is that a catfish on the bottom? Or is that a group of rocks? If you have a $2,000-$3,000 Lowrance or Humminbird unit and feel you need to learn more about sonar interpretation, this is what I hope will be the thread for you as well to cover a broad range. The things I have learned in just the last 2yrs have helped me tremendously and it's taken scratching and clawing to get the information. Why? Because I didn’t have someone to simply take a trip and show me advanced knowledge of what to look at and how to interpret it. I'm hoping this thread will "balloon" into something big and useful for all anglers. I believe others should teach and share the knowledge in order to pass it on to perpetuate the sport. Not, give away secrets in fear that they will have stiffer competition in tournaments because.........if it were easy it would be called "catching" and not "fishing". Am I right? :-) Here are a few highlights as this subject is very broad and there is already a lot of info available on the internet)FOR THE NOVICE - HOW TO READ SONAR:(If this is not you, skip forward to the next level) First…..This needs to be broken down into categories:1) Basic sonar understanding2) Advanced sonar3) Drop-shot presentation4) Side Imaging5) 360-degree imaging (I’m not covering much here as I think it’s a gimmick personally until the technology gets better) BASIC SONAR UNDERSTANDING Can't read a lot? Here is a great video http://youtu.be/KTacpPjjWiU What is a cone angle? The cone angle is how your transducer sends out a signal. The transducer sends a hi-frequency ticking sound in the shape of a cone. The signal bounces back to the transducer as it hits an object and since a fish is arch shaped in nature, it creates an arch on the graph. Why does it matter what frequency I use?What’s a frequency? (haha) Some units use 200kHz and some use up to 400 or even 800kHz. This hi-frequency, the more detailed the image presented on your graph but it also narrows the cone shape so you will cover less area. For users with structure scan or “down scan imaging”, your transducer emits in an oblong shape which is basically a “squeezed cone shape”. Look up your manual for more info on your particular unit. What’s ping speed? Ping speed is the rate of speed the transducer sends a signal. The faster the signal, the more accurate the information which is great for dropshoting (well I think so anyway) What is chart speed? Chart speed is just that, how fast the information is displayed on a chart What is Sensitivity? Should it be on auto? (typically yes) Most know this is how sensitive the unit picks up smaller signals What is noise rejection? Typically, this is rejecting electrical noise and mixed signals from aerators, trolling motors, etc. It can decrease the sensitivity I personally turn noise rejection off when I use 800kHz on my DSI unit NOW…..what is a chart?When you’re watching your fish finder, you see arches or “fish symbols” scroll across. What you’re looking at is a caption of a moment in time. Ever see a polygraph on TV? Or heart monitor on a movie when the patient flat lines and the heart stops? This is essentially what you’re seeing with your fish finder. If your unit is equipped with it, you will have lines appearing on the right hand side. What you’re seeing there is “live feed”. This is essentially the old “flasher sonar” that your grandpa or dad used back in the day. It’s vertical now instead of 360 degrees. Any of this making sense? If not, go back and re-read. J Think “chart readout” or watching a scroll of paper feeding out of a machine while it prints lines on it. That’s essentially what your graph is showing in both traditional sonar and the new structure scan or down scan. That’s the basics. Pretty easy huh? It took me forever to understand the “heart monitor” or “polygraph” thing. I had to have a guide show me on his fancy sonar while he taught me how to dropshot before I “got it”. Once I “got it”, the doors started opening. ADVANCED SONAR(This is where I need help from other forum members)So if you have structure scan or down imaging or even side scan, you probably already know what it is and how it works. Or at least the basics.When looking at structure/down scan imaging, you’re seeing a higher frequency signal sent to your unit which gives a higher definition reading. Why can’t I see fish arches with structure scan? Well, since it’s a higher frequency the signal is not as “muddy” as it is with traditional sonar so the arches are smaller. Think of it this way. When you show a split screen or when you switch from a lower frequency to a higher frequency, you will see trees show up sharper and crisper. To me, 800kHz is great for showing sunken school buses online and sunken bridges. (hahaha). These show hi-definition of the bottom structure but not as much on fish arches. Its best to get a good reading on what you’re seeing for both bottom structure, hard pan or soft, depth, brush piles, rocks, etc. as well as fish arches. That’s why units that show both traditional sonar and structure scan on split screens is the best way to learn between the two. DROPSHOT PRESENTATIONEver wanted to learn how to do this beter? I know I did. I had a local guide take me out one day and gave me a quick lesson on what I was seeing underwater and within 2mins, I “got it”. I hope this explanation helps you “get it” as well. Remember when I mentioned the bars on the right side of your graph being a “live feed”?? If not, go back up to “Now, what is a chart” section and read that again. That’s essentially dropshot presentation. You drop a bait or a jig, or even live bait below your transducer and watch the object fall “live” by watching the little lines on the right side. You’ll see your bait dropping and then you’ll see a diagonal line on your graph. THAT is the history or the readout of where your bait was as it was falling. It doesn’t mean your bait fell at an angle, it’s just a readout of the “cone angle”. (re-read cone angle above). In order to drop shot or see your bait of any kind on the graph, it MUST be within the cone angle. I suggest using the lowest frequency possible to create a “WIDE” cone angle. The deeper the water, the larger your cone will be. If you’re in 10ft, your cone diameter will be much smaller in size than it will be in 30ft. SIDE IMAGINGHere’s a good link that explains what this is and how to use it. http://youtu.be/yNucS1bniIw 360 DEGREE IMAGINGEver see a radar tower on a ship or at an airport? Ever see a radar scope on a movie where you see the plans or little “blips” on the scope in the movie TOP GUN where you can see the images projected on the scope representing the planes? Well……….that’s the same theory of 360 imaging. A transducer is lowered below the boat and scans the area up to a particular distance and projects and image. Problem is, it’s not as advanced as side imaging and structure scan so the images are a bit “blury”. If you understand what you’re looking at and how to use it, it can be a “gamechanger” as KVD says. Well, that’s a start of a very broad subject with a “simplistic” view or explanation. blacknoseddace 1 Need marine repair? Send our own forum friend "fishinwrench" a message. He will treat you like family!!! I owe fishinwrench a lot of thanks. He has been a great mechanic with lots of patience! Link to comment Share on other sites More sharing options...
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