Just getting started in the concept of s/i and d/i of sonar units and have not been able to determine the position of the boat in relation to the screen shots. in a side imaging screen is the boat considered to be in the center of the screen shot???? I understand that d/i screens are scrolling right to left as the boat moves forward and the area coverage is determined by the cone degree and the depth of the water but where is the boat in relationship to the screen shot. Any info or links to videos to understanding this is appreciated.