forgot 5 6 & 7.

http://i49.photobucket.com/albums/f2...g5Fig6Fig7.jpg


Note: this may be old news to veterans but this may help some people that are new to using a depth sounder. I don't really call them a fish finder because they do more than that.

Learning to interrupt the readings on your sounder's display is key to understanding the bottom structure of your lake.

This is an important picture to understanding the concept of how sonar works or how it won't work. Note: Fish outside the cone of sound waves are not going to be visible. And fish on the edge of the cone of sound waves are going to appear to be deeper than they actually are. They will appear to be much deeper when the cone angle is greater than 20 deg.

The fish arch principle is a result of the fish entering the cone of influence and appearing to be further or deeper and as the boat goes over the fish and the fish nears the center of the cone of influence of the sounds the fish will appear to get shallower. That corresponds to the peak of the fish arch seen on the screen. As the boat passes through the fish and the fish is about to exit out of the cone of influence of the sound waves the fish will appear to be further away or deeper. This will be the tail end of the fish arch. Note the fish has to go through the center of the cone of influence of the sound waves to make a perfect fish arch on the screen.

Fish slicking through the edge of the cone of influence of the sound waves will not make a perfect arch on the screen.

Boat speed, screen scrolling speed settings and movement of the fish will effect the way the arch is displayed on your screen.

Most may already know this but for those that are new to fishing this may be of interest to you.