A portable path guidance system

In recent years rapid technological advances have led to the development of several electronic aids to navigation and considerable research has been carried out in coupling positional information to automatic pilots, with varied success in application. Probably the most noteworthy, albeit in the aircraft industry, has been in the automatic approach and landing of air- craft, where precise positional information in both height and locality has been geared to the automatic pilot to enable accuracies greater than those achieved in manual pilotage to be flown coupled with reliability figures certainly comparable and often claimed to be better than those achieved in manual flying.