Putting this up since people were confused about how to read sonar properly. Explaining it is kind of hard but understanding it is easy, once you catch on you'll wonder how you ever lived without it. The system is taken from Elite/Frontier series which used exact same system to describe position of objects in 3D space relative to your vehicle. Dots on radar are positioned in 3D, but to help you understand where each dot really is, there is the green plane and white lines. The green plane is always at your altitude and the center of it is your vehicle's position. Each white line is connected to it's dot on one end, and to the plane on other. These lines extrude up from their dot if the object is below you, or down from the dot if the object is above you, and it's length helps you understand the object's altitude compared to yours.