It might help you to think about it the simplest of terms. Sonar is nothing but a measuring device. It determines how far objects are away. Then the software performs the graphic functionality to display on the screen. For example, when you set the screen to display 100' left and right, it has no effect on the sonar scanning. The transducer sends out the sound the same distance all the time, which is determined by the capabilities of the unit/transducer and frequency setting. It is only the user that is setting the viewing range on the screen. That being said, an example would be; boat is in 80' of water, screen is set to view 100' left and right. The screen will display black space on both sides of the boat center line. This black space is the water column directly below the boat down to the bottom, NOT the water column 80' to the left and right of the boat. So if the screen displays a stump on the bottom at the right side 80' line that stump is NOT 80' to the right of the boat. It is directly 80' down below the boat. If that stump is shown at the 90' line to the right of the boat, it is NOT 90' to the right of the boat, it is only a few feet to the right of the boat. This is where the math would come in to determine distace right and left based on depth/distance, etc. The other consideration would be the angle of the bottom. Main thing to remember is the sonar transducer is measuring distance within its beam width on a straight line all the time and adjusting the screen is only changing the viewing parameters, not the scanning parameters.