Operative control of positioning availability of satellite navigation system user

This paper is devoted to the method of operative control of an positioning availability of object by means of the wide area differ-rential subsystem of global satellite navigation systems GPS and GLONASS. Estimation of full probability of decision of navigation determinations with given accuracy is the base of this method. Method can be used for efficiency increasing of control integrity algorithms of satellite navigation systems and their differential subsystems in conditions of sudden disadvantage geophysical factors.