Patent ID: 7054739

Claim:
A navigation apparatus comprising: a radio receiver; at least one directional antenna communicatively coupled to the radio receiver, the directional antenna providing relative bearing information to the radio receiver; a navigation computer including a memory and a processor, the navigation computer being communicatively coupled to the radio receiver to receive relative bearing information; a database stored in the memory, the database including a record of position information and a record of radio frequency information for a plurality of known radio transmitters; a set of instructions stored in the memory and executable by the processor to cause the radio receiver to tune to at least three known radio transmitters selected from the plurality of known radio transmitters using the record of radio frequency information; a set of instructions stored in the memory and executable by the processor to use relative bearing information from the at least one directional antenna to the at least three known radio transmitters and to use the record of position information to calculate a first reference position; a set of instructions stored in the memory and executable by the processor to calculate a true bearing from the first reference position to a known position using the first reference position and a known position of at least one of the at least three known radio transmitters; and a set of instructions stored in the memory and executable by the processor to use relative bearing information from the at least one directional antenna to the at least three known radio transmitters and to use the true bearing to calculate a true heading.