Buildingthe collinear antenna with ground plane

i am confuse that If i will build antenna that simulated with ground plan . I must build this ground plane or not ? . i think it's seem like reflector as earth plan and no building. or Depending on What size of antenna ?

Thank you

Collinear antennas use λ/2 elements and theoretically don't need a ground plane.
If you add a ground plane at particular distance the antenna pattern would change. So, without a ground plane the antenna focuses more energy towards the horizon (lower take-off azimuth angle), thus not wasting any energy towards unwanted areas like the sky.
The ground plane gives higher azimuth angle and will reduce the minor lobes in the pattern, which somehow can be tolerated when the antenna is elevated.