Navigation equipment for agricultural vehicles and implements; guidance systems for vehicles including agricultural vehicles and agricultural implements; steering apparatus and assemblies for vehicles including agricultural vehicles and agricultural implements; computer hardware and software for navigation, guidance and steering equipment; GPS receivers; transmission apparatus in this class including GPS transmitters; aerials in this class including GPS aerials; computer controlled steering systems for agricultural vehicles, machinery and apparatus; computer controlled steering devices for agricultural machines, vehicles and apparatus; electronic control, monitoring information sensing and information display systems for use in agriculture