Navigation system using external monitoring

A local area augmentation navigation system for determining the authenticity of the LAAS signal transmitted from a VDB transmitter, the system comprising:

• at least one reference station at a known location, each reference station receiving a GPS signal from a GPS constellation and collecting and outputting pseudo-range data from the GPS signal;
• a master station receiving the pseudo-range data from the at least one reference station, the master station forming a correction message from the pseudo-range data and the known location of the at least one reference station, the master station broadcasting the correction message;
• at least one monitoring receiver at a known location receiving GPS signals from the GPS constellation and receiving the correction message broadcast by the master station;
• wherein the monitoring receiver communicates with the master station to verify the authenticity of the correction message broadcast by the master station and monitor the OPS satellite integrity in field;
• and,
• a LAAS receiver receiving the correction message broadcast by the master station as well as a GPS signal from the GPS constellation and calculating the location of the LAAS receiver with the correction message and the GPS signal.