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The TOTAL length of the antenna, antenna lead-in wire AND ground connection wire cannot exceed 3-meters.
Most of us (I believe) think this means any above ground visible lengths of metal. We take it for granted that anything IN the ground, BELOW ground is not counted because it’s not visible.
Your project description would all be above ground and visible. Being horizontal is not a safety zone.
But you could obscure the lower half of your antenna with a fog machine.