Magnetic navigation system

Claim 2

A magnetic navigation system comprising: first means for determining the total ambient earth''s magnetic field including a total field optically pumped magnetometer for generating a first output signal indicative of the total field strength; and second means connected to receive the output signal of said magnetometer for providing a first compensation signal to said first means whereby said first means provides a second output signal indicative of the horizontal component of the total field strength.

Claim 3

A magnetic navigation system according to claim 1 wherein said second means further comprises: a bandpass filter connected to receive the signal from said magnetometer; a servomotor operatively connected to said filter for being driven by the output of said filter when the output exceeds a predetermined level; a potentiometer mechanically connected to the output of said servomotor for being positioned by said servomotor; a fixed current source being provided to the input of said potentiometer; coil means connected to the output of said potentiometer and positioned to provide a field flux to said magnetometer along a predetermined axis; and signal generating means connected to said coil means for providing an electrical signal of the same frequency as the bandpass of said filter.

Claim 4

A magnetic navigation system according to claim 2 wherein said coil means further comprises: a first Helmholtz coil connected to receive the output of said potentiometer; and a second Helmholtz coil connected to receive the output of said signal generating means.

Claim 5

A magnetic navigation system according to claim 3 further comprising: a first switch interposed between said signal generating means and said second Helmholtz coil; and a second switch interposed between said fixed current source and said potentiometer.

Claim 6

A magnetic navigation system according to claim 4 further coMprising: third means including a shunting switch interposed between said second switch and said first Helmholtz coil across said potentiometer for providing a known second compensation signal to said magnetometer along a vertical axis.

Claim 7

A magnetic navigation system according to claim 5 further comprising: computer means operatively connected to the output of said magnetometer arranged for solving the equations: Delta F F - F'' wherein F is the value of the output signal of the magnetometer indicative of the total ambient earth''s magnetic field and F'' is the output signal of the magnetometer after the second compensation signal has been provided, I sin 1 Delta F/ Delta Fz wherein Delta Fz is the value of the second compensation signal provided to the magnetometer and I is the inclination angle, and Fz F sin I wherein Fz is the vertical component of the ambient earth''s magnetic field.

Claim 8

A magnetic navigation system according to claim 6 further comprising: fourth means operatively connected to provide a known third compensation signal to said magnetometer along a horizontal axis.

Claim 9

A magnetic navigation system according to claim 7 wherein said fourth means further comprises: a third switch connected to said fixed current source; and a third Helmboltz coil in orthogonal relationship to said first and second Helmholtz coils connected to said third switch.

Claim 10

A navigation system according to claim 8 further comprising: a directional gyro operatively connected to said computer means for providing a signal indicative of true heading.

Claim 11

A navigation system according to claim 9 wherein said computer means is further arranged to solve the equations: Delta Fxy Fxy - F''xy and D TH - cos 1 Delta Fxy/ Delta Fx wherein Fxy is the horizontal component of the earth''s ambient magnetic field, F''xy is the component sensed by the magnetometer after providing the third known compensation signal, D is the declination angle, TH is the true heading and Delta Fx is the known value of the third compensation signal.