The German air law includes in their legal definition of a "Luftfahrzeug", which is the equivalent of an aircraft, other devices intended to operate in the airspace if they are capable of being operated more than 30 meters (100 ft) above ground or sea level.
Does an equivalent to this 100 ft threshold exist in ICAO documents or other international regulations? If yes, where?
The background of my question is: if an unmanned aircraft has a technical feature preventing it from flying above 100 ft, would it still qualify as an aircraft and would all regulations about aircraft apply?
I would also like to know, why the 100 ft threshold was put into the German (or other) laws. I could image that it was intended to exclude wing in ground effect crafts from the aircraft category. Is a wing in ground effect craft an aircraft according to ICAO definition?