Why are there red lines at ski jumping?

Answer 1

They're to help the jumpers see the ground and see how close they are to the ground. Flat light on snow can make it very difficult to judge distance.

Answer 2

the red line is the k point where the hill goes from convex to concave, once you get past that it starts to hurt to land. the line helps hill markers to see the distance an athlete jumps

Answer 3

So they have a point of reference to the ground. The branches supply texture to the snow, this way freestyle skiers can tell how far they are to the ground.