Snowkiting uses skis or snowboards plus a kite like you would use for kitesurfing. A lot depends on the weather, and you need a gusty wind to get any height at all. It also helps if you've got one of the best in the sport to instruct you. We meet Inga Wopker, Germany's champion snowkiter of 2013, and her class at the Feldberg in the Black Forest region.