A method for positioning or navigating an object associated with a local positioning system, a local reference receiver and a wide-area differential satellite positioning system, comprising: determining a first position of the object in accordance with carrier-phase measurements using the wide-area differential satellite positioning system in a first mode of operation; determining a second position of the object in accordance with information received through a first communication link from the local positioning system in a second mode of operation, wherein the local positioning system comprises one or more active or passive landmarks and is based on a time of flight for signals and/or a Doppler frequency shift; and determining a third position of the object in accordance with information received through a second communication link from the local reference receiver using real-time kinematic positioning in a third mode of operation; wherein the first mode of operation is used when communication with the local reference receiver and the local positioning system is lost, the second mode of operation is used when communication with the local positioning system is available, and wherein the third mode of operation is used when the communication with the local reference receiver is available and the communication with the local positioning system is lost; and wherein, when communication with the local positioning system is available, the first and second modes of operation are used substantially simultaneously, and a difference between the second position and the first position is used to initialize a floating ambiguity value in the carrier phase measurements for the wide-area differential satellite positioning system. determining a first position of the object in accordance with carrier-phase measurements using the wide-area differential satellite positioning system in a first mode of operation; determining a second position of the object in accordance with information received through a first communication link from the local positioning system in a second mode of operation, wherein the local positioning system comprises one or more active or passive landmarks and is based on a time of flight for signals and/or a Doppler frequency shift; and determining a third position of the object in accordance with information received through a second communication link from the local reference receiver using real-time kinematic positioning in a third mode of operation; wherein the first mode of operation is used when communication with the local reference receiver and the local positioning system is lost, the second mode of operation is used when communication with the local positioning system is available, and wherein the third mode of operation is used when the communication with the local reference receiver is available and the communication with the local positioning system is lost; and wherein, when communication with the local positioning system is available, the first and second modes of operation are used substantially simultaneously, and a difference between the second position and the first position is used to initialize a floating ambiguity value in the carrier phase measurements for the wide-area differential satellite positioning system.