Interpreting the bottom
The bottom is represented by a solid line at the bottom of the screen and usually produces a strong echo. As a general rule: the thicker the bottom line, the harder the bottom.
SonarInterpreting bottom
Hard bottom.
Soft bottom.
Multiple bottoms
It is possible that the sonar signal can make 2 or more complete trips: hitting the bottom, bouncing off the vessel, and then reflecting off the bottom again. This is most common in shallow waters, or if the bottom is very hard.
Hard bottoms
A hard bottom produces a stronger sonar signal which is displayed as a thicker, solid bottom line, primarily consisting of the color used to represent the strongest returns (e.g.: the darkest color). Hard bottoms may produce a more prominent second bottom line onscreen.
Figure 1. Examples
Hard structure like rocks (2) and wrecks (1) will be displayed as solid returns connected to the bottom , producing an irregular line with peaks and troughs. Tails (3) protruding below the bottom line are another sign of a hard bottom.
When trying to identify a hard bottom, you can set the sonar depth to 3 or 4 times the actual depth and a second or multiple bottoms should appear under hard bottom areas.
Soft bottoms
A soft bottom produces a weaker sonar signal, which is displayed as a thinner overall line. Soft bottoms can also produce voids under the bottom line, instead of weaker returns.
Mixed bottom
A mixed hard and soft bottom may result in a mixture of strong and weak returns.
Sonar settings can usually be changed to use different, or inverted color palettes. Ensure that you know which colors are being used to represent strong and weak signals.
Bottom line
The bottom line feature displays a white line along the bottom, which helps distinguish between the bottom and targets close to the bottom.
