Magnetic field gradient navigation aid

A method for determining a geographical location, the method comprising:

• under control of at least one hardware processor and memory configured with executable instructions:
• identifying, using a vector magnetometer that is onboard a moving platform, a plurality of magnetic field gradients, the magnetic field gradients being continuously measured while the moving platform is traveling along a path to a destination;
• identifying a sequence of magnetic field gradient measurements in the plurality of magnetic field gradients for specific positions on the Earth that correspond to a path traveled by the moving platform;
• comparing the sequence of magnetic field gradient measurements for the path to a reference magnetic field gradient map stored in a data store, the reference magnetic field gradient map describing the Earth's magnetic anomaly field;
• identifying a trajectory derived from the reference magnetic field gradient map that correlates to the sequence of magnetic field gradient measurements, the trajectory having known geographical coordinates;
• determining the geographical location of the moving platform based on the known geographical coordinates of the trajectory;
• and
• updating an inertial navigation system (INS) of the moving platform with the geographical location in order to mitigate INS drift.

A system for determining a geographical location of a moving platform, the system comprising:

• a vector magnetometer operable to measure a plurality of magnetic field gradients from the moving platform, each magnetic field gradient corresponding to a position on the Earth, the magnetic field gradients being continually measured while the moving platform is traveling along a path to a destination;
• a data store comprising a reference magnetic field gradient map that describes the Earth's magnetic anomaly field;
• and
• one or more processors and memory operable to:
• identify the plurality of magnetic field gradients, the magnetic field gradients being continuously measured while the moving platform is traveling along a path to a destination;
• create a sequence of magnetic field gradient measurements from the plurality of magnetic field gradients that correspond to the path traveled by the moving platform;
• compare the sequence of magnetic field gradient measurements for the path to a plurality of possible trajectories derived from the reference magnetic field gradient map;
• identify a trajectory from the reference magnetic field gradient map that correlates to the sequence of magnetic field gradient measurements, the trajectory having known geographical coordinates;
• determine the geographical location of the moving platform based on the known geographical coordinates of the trajectory;
• and
• update an inertial navigation system (INS) of the moving platform with the geographical location in order to mitigate INS drift.