Si Pictures

[Moveon]

Note the stream or roadbed that crosses the SI picture from left to right. It's the darker area that's visible from the brighter parts parts of the picture.

Areas that reflect the sound waves better will have a brighter return on the screen. Areas that absorb the sound waves will appear darker in color.

Objects that stick up off the bottom will cast shadowns on the side opposite of where the sound waves are coming from. Just like a flash light beam on a tree will cast a shallow on the other side of the tree.

Fish suspended in the water column will also cast shadows. The distance from the fish to the shadow can help you tell how far off the bottom the fish is suspended. The higher in the water column the farther the shadow will be from the fish. Fish will appear as tiny white dots in the water column and their shadows will show up on the brighter parts of the bottom some distance to the side of the center line. The center line in the pictures represents the path of the boat/sonar/transducer. The top is the recent sonar pings or images and the bottom is the history. The farther down the page the further back in history the recording was made on the screen. Old sonar pictures will drop off the bottom of the screen as the new data appears at the top of the screen. Everything to the right of the center line will be what was shown on the right side of the boat's path. And vise versa for the left side. The humminbird can show one sides data or the others side only or both sides like in this picture.