Patent ID: 8265809

Claim:
An apparatus comprising: a sealed hull having at least first and second electrodes; a propulsion unit for moving the hull through a conductive liquid while the hull is submerged under a surface of the conductive liquid; and a control system coupled to the electrodes and configured to monitor voltages at the electrodes, wherein the voltages are the result of the motion of the conductive liquid with respect to the magnetic field of the Earth; control the propulsion unit such that the electrodes are moved along a reciprocating course during voltage monitoring, wherein the reciprocating course includes at least a one hundred eighty degree change in horizontal heading and a plurality of depths in the conductive liquid; and wirelessly transmit signals representative of the motion of the conductive liquid, relative to a frame of reference that is fixed with respect to the surface of the Earth, within which the hull resides to a location remote from the hull while the hull is on the surface of the conductive liquid, wherein the control system is further configured to remove from the signals portions representative of the voltage generated by motion of the apparatus with respect to the magnetic field of the Earth and the voltage of the electrodes in a conductive liquid.