Not too long ago I put up a couple of videos from YouTube. The first video is of a semi-pro with a helmet camera, but it is a pro setup. The video comes along with commentary from the announcers. The skier runs a downhill race course and catches every bit of air one would expect.
The second video is an amateur skier with a handheld video camera skiing down the same ski run. He is not running a course but is free skiing. However, watch the video, you can see how is skiing by watching his shadow. In addition, he includes the raw audio, so you can hear him verbally react to the jumps (on top, he doesn’t seem to catch much air down course), and has he starts off down the serious headwall.
Notice how the perspective changes as he is skiing through the terrain park and the headwall. The terrain park appears flat, while the headwall is noticeably sloped downhill. Neither portion of the course is flat, but it takes the extreme slope of the headwall to show up on the camera. Another measure you can use to figure out how steep the headwall is, is the shadow he casts, notice how far down the headwall that shadow reaches.
Even after all of that, the ease by which he handles that run and by the flattening affect of the camera, I sit here thinking I can handle that run. I know I can get myself up to it, but it would take some work, and I need to learn to let loose on steeps, and not not be defensive.