Before revision: It uses a minimum of six satellites to not only detect a possible faulty satellite, but to exclude it from the navigation solution so the navigation function can continue without interruption.
After revision: It uses a minimum of six meassurements which can be achieved with 6 satellites or 5 satellites with baro-aiding to not only detect a possible faulty satellite, but to exclude it from the navigation solution so the navigation function can continue without interruption.