In the 2D radar, each "dot" could have a bottom-down view of the ship with 1 pixel per 1/16|1/8 ship size.
I would approve the hight be visible. (This game is about 3D space, not 2D 20th century naval warfare)
Easily possible by showing a tangential line.
ship x,y,z = from yours;
target x,y,z...