In ground trampolines can be circular or rectangular. It is build just like a foundation and the trampoline is placed on top of the "foundation" walls.
Solar panels are set on top of the roof of a house a building or in an open area supported by posts. and are always facing the sun which is east to west. Most solar panels move with the direction of the sun. So in the morning the solar panels will be facing east and will rotate west toward the sunset.