Sonar apparatus for the location and display of features on the underwater floor in front of a boat includes port and starboard transducer units each containing transducer arrays. A transducer interface and a visual processor process signals from the transducer arrays to generate image data for a display. The transducer arrays emit sound waves into non-overlapping segments of water, reflected by the underwater floor back to the transducer arrays, which convert them to electrical signals. The electrical signals are processed to calculate a three-dimensional position of each point on the underwater floor. The sonar apparatus performs interpolation using the three-dimensional positions of the reflecting points within the segments to calculate three-dimensional positions of points on the underwater floor between these segments. The three-dimensional positions of the points are then used to generate image data showing the underwater floor in front of the boat.