Abstract: A system for differential navigation of an autonomous vehicle in the location with the limited visibility of the sky is disclosed. The system employs a plurality of satellites, a plurality of ground transmitters, and a base station. Different configurations for the minimum number of the satellites and the minimum number of ground transmitters are disclosed.

Abstract: A stopper for use in a substantially cylindrical bottle opening is disclosed. The stopper is made of a synthetic elastomer body with a portion with a substantially cylindrical shape to seal the bottle opening. The elastomer body also contains a fiber portion or a plurality of fiber portions oriented substantially longitudinally in the elastomer body. The synthetic stopper is preferably designed to replace traditional wood bark corks in wine bottles. In one embodiment, the fiber reinforcement is in the form of a porous plug surrounded by an elastomer skin. In another embodiment, fibrous strips are dispersed throughout the stopper structure. The method of producing a stopper for use in a substantially cylindrical bottle opening is also disclosed as is a method of protecting a liquid in a bottle with a fiber reinforced synthetic elastomer stopper.