UE4 - How to spawn enemies over a landscape, not under while using a big box to spawn at random?

Hi, i created a BP with a box spawner, it creates random enemies inside the box, so i can make the spawner as big as i want and enemies Will spawn in a random place, my problem is that, if i created a landscape, ground limit is alwasy off, because of mountains etc, so if i locate the spawner to cover the entire landscape, it might also go under the landscape, and then enemies are also spawned under the mesh, how can i make enemies not to be able to spawn under a mesh, jut over a mesh? Trying to use a default spawner option to not spawn if colisio wont work, since under a landspcape it might not colision too.

Please help with BP images if posible.