Sorry for the delay wacopops. I meant to reply to this sooner.
First off, I don't consider myself an expert by any means. I can however say that I've done a ton of research online. I've spent countless hours looking for detailed information and studying that information. I've also coupled this with a tremendous amount of time on the water using what I've learned and experimenting. I'm not sure what brand you run. I run Lowrance Gen2 Touches and that's all I'm familiar with at this point. Here's what I can share with you that seems to work for me thus far.
I almost always scan at 800khz instead of 455khz. It won't scan out as far as 455 but it gives a clearer picture. Surface noise and noise rejection are almost always turned off. I've experimented with these two setting toggling them back and forth on different days on the water and I don't really see any difference. My thought on it is if there's nothing to gain then I want to see everything below me and not filter it out.
One of the biggest things that really got me going and identifying what's beneath me was finding a palette that I liked. I believe if I remember correctly I have it set on 9 and it's blue. During my research I've noticed a wide variety of palettes used and fortunately we have many to choose from. Experiment and find the one you like. Scan some cover and structure below you like a tree on a creek bend. Go back over it a few times and try different ones until you find one the you trust and feel comfortable with.
Now let's talk about contrast. This is very important. This is what ultimately makes everything below you as clear as the sky or clear as mud. The default setting isn't that bad and does a decent job for the most part. What I've noticed though is that most times my picture will not have just the right amount of contrast to clearly define what's below but is usually close. Not having enough and everything will be too dark and will not outline what's beneath you. Too much is the opposite and will white everything out. The sweet spot is having enough to clearly show and define cover, structure, fish and the bottom of the lake. To combat this put it in manual and tweek it to maximize clarity. Deeper water I may be anywhere from 74 - 67 and in shallow parts I may lower it all the way down to 62. Once you get use to it it only takes a couple of seconds to adjust.
Speaking of scanning different depths of water you'll want to adjust how far out you're scanning during this process. In deeper water you'll want to look further out and as you move into shallow water you'll want to bring it in. Structure scan works by projecting a signal down then out. This is very important and I'll explain why. Looking at your graph the line in the middle is cavitation from your prop. The dark area on both sides of this is the water column below you and outward a little bit then the bottom of the lake. If you see a ball of shad to your left and your maker on the graph says they're 40 feet out and you're in 20 feet of water they are actually 20 feet to your left. You have to subtract the depth of water from the marker. I remember scanning banks near deep water and not seeing them wondering what the heck was going on. I scan anywhere from as high as 100 to as low as 20. I'm usually in the 60 - 30 range though. A good rule of thumb is to scan 2 to 3 times the depth of water you're in.
Other tips I can think of is brighter areas are harder bottoms and vice versa. If you're graphing for good size fish you want to look for white lines. If they're off the bottom or suspended you see a shadow below them. Something I've been doing lately now that I'm more use to my graphs is to look at my traditional sonar to see how big the fish is once I see them on side or down imaging. Also, look at your sonar or down imaging to see how much they are suspended off the bottom. Another thing I would recommend if you don't have it is put a HDI transducer on the bow for down imaging. This really takes the guess work out of traditional sonar. You'll know exactly what's below you in an instant.
Experiment with your graphs and do a little research. It will go a long ways in a short time if you do.
I hope this all helps and good fishin'...
Edited by Mayo (12/09/15 09:24 PM)