Train flyover

[ignis]

Hi,

I've been toying for quite a while with the idea of flying an FPV quad with a GoPro over a moving train. There is a very picturesque stretch of tracks about 60km outside the city I live in, really beautiful landscapes with fjords, mountainsides and scattered farms and houses.

What I'm worried about is the slipstream. Naturally I'm not talking about flying right over the train, I'd want to be 5-10m above it. But the train is big, and air current around it must be pretty massive. Fly low enough and it will throw the quad around like a speck of dust. Fly too high, and the perfect shot is lost.

How high do you guys think I'd have to fly to not be affected by the train's slipstream?

[Goldenhour]

I read about a AP crew doing an advertisment for a port that had exactly that shot in it. As the train approached they lifted off about 5 meters to the side. As the train approached they did a 180 pan to see the train leaving them. They were about 10 meters high I'd say. I've thought of doing that same shot save for the copter sitting on the tracks as the train approaches lift off and pan.
From the picture below I'd assume you DONT want to be in the air at the ass end of the train.
I think you'll be fine doing it from the side and staying well above the train. It's a dramatic shot you don't see too often.
I actually followed the links from Helifreak here. They are a working AP company outside of the US. Been around a while. Cant remember the name.