Abstract: Technology for determining a geographical location is described. A sequence of magnetic field gradient measurements can be identified for specific positions on the Earth that correspond to a path traveled by a moving platform. The sequence of magnetic field gradient measurements for the path can be compared to a reference magnetic field gradient map. A trajectory derived from the reference magnetic field gradient map that correlates to the sequence of magnetic field gradient measurements can be identified. The trajectory can have known geographical coordinates. The geographical location of the moving platform can be determined based on the known geographical coordinates of the trajectory.

Abstract: Technology for performing magnetic field gradient measurements is described. The magnetic field gradient measurements for specific positions on the Earth can be performed from a moving platform. The magnetic field gradient measurements can be identified as being affected by a level of error that exceeds a defined threshold. A correction value can be generated to compensate for the error in the magnetic field gradient measurements. The correction value can be applied to the magnetic field gradient measurements in order to obtain magnetic field gradient measurements with a reduced level of error.

Abstract: A method of performing geolocation of receivers, transmitters, and conductive objects includes detecting, with one or more receivers, magnetic field signals generated by one or more transmitters, with each transmitter including two or more co-located coils that are electrically unstable and unbalanced, and that have a mechanically stable orientation with respect to one another. The magnetic field signals from each of the two or more co-located coils of each of the two or more transmitters are decomposed into individual magnetic field components. A set of invariant scalar values that are independent of orientation of one or more magnetic antennas associated with the one or more receivers are calculated from the individual magnetic field components, and the position of an object is determined using the set of invariant scalar values.

Abstract: A communication system and a method of fabricating a communication system are described. The communication system includes a transmit antenna including two or more symmetric coils wound around a closed-loop magnetic transmitter core, the transmit antenna configured to transmit an outgoing signal of very low frequency (VLF) or ultra low frequency (ULF) energy. The communication system also includes a receive antenna including two or more coils formed from two or more wires wound around a closed-loop magnetic receiver core, the receive antenna configured to receive transmitted VLF or ULF energy as an incoming signal. The communication system also includes a processor to process the outgoing signal and the incoming signal.

Abstract: Technology for determining a geographical location is described. A sequence of magnetic field gradient measurements can be identified for specific positions on the Earth that correspond to a path traveled by a moving platform. The sequence of magnetic field gradient measurements for the path can be compared to a reference magnetic field gradient map. A trajectory derived from the reference magnetic field gradient map that correlates to the sequence of magnetic field gradient measurements can be identified. The trajectory can have known geographical coordinates. The geographical location of the moving platform can be determined based on the known geographical coordinates of the trajectory.

Abstract: Technology for performing magnetic field gradient measurements is described. The magnetic field gradient measurements for specific positions on the Earth can be performed from a moving platform. The magnetic field gradient measurements can be identified as being affected by a level of error that exceeds a defined threshold. A correction value can be generated to compensate for the error in the magnetic field gradient measurements. The correction value can be applied to the magnetic field gradient measurements in order to obtain magnetic field gradient measurements with a reduced level of error.

Abstract: Methods and apparatus for producing multi-spectral images having variable (non-uniform) magnification over the lateral extent of the image. In one example, a multi-spectral imaging system includes a first sensor sub-system configured to receive electromagnetic radiation in a first spectral band from a scene and to provide a first image signal, a second sensor sub-system configured to receive electromagnetic radiation in a second spectral band from the scene and to provide a second image signal, a processor coupled to the first and second sensor sub-systems and configured to produce a first image of the scene from the first image signal, and a second image of the scene from the second image signal, the second image having a variable lateral magnification, and a display coupled to the processor and configured to display the second image overlaid with the first image.

Abstract: A communication system and a method of fabricating a communication system are described. The communication system includes a transmit antenna including two or more symmetric coils wound around a closed-loop magnetic transmitter core, the transmit antenna configured to transmit an outgoing signal of very low frequency (VLF) or ultra low frequency (ULF) energy. The communication system also includes a receive antenna including two or more coils formed from two or more wires wound around a closed-loop magnetic receiver core, the receive antenna configured to receive transmitted VLF or ULF energy as an incoming signal. The communication system also includes a processor to process the outgoing signal and the incoming signal.

Abstract: Methods and apparatus for producing multi-spectral images having variable (non-uniform) magnification over the lateral extent of the image. In one example, a multi-spectral imaging system includes a first sensor sub-system configured to receive electromagnetic radiation in a first spectral band from a scene and to provide a first image signal, a second sensor sub-system configured to receive electromagnetic radiation in a second spectral band from the scene and to provide a second image signal, a processor coupled to the first and second sensor sub-systems and configured to produce a first image of the scene from the first image signal, and a second image of the scene from the second image signal, the second image having a variable lateral magnification, and a display coupled to the processor and configured to display the second image overlaid with the first image.

Abstract: A method of performing geolocation of receivers, transmitters, and conductive objects includes detecting, with one or more receivers, magnetic field signals generated by one or more transmitters, with each transmitter including two or more co-located coils that are electrically unstable and unbalanced, and that have a mechanically stable orientation with respect to one another. The magnetic field signals from each of the two or more co-located coils of each of the two or more transmitters are decomposed into individual magnetic field components. A set of invariant scalar values that are independent of orientation of one or more magnetic antennas associated with the one or more receivers are calculated from the individual magnetic field components, and the position of an object is determined using the set of invariant scalar values.

Abstract: A method of navigation includes receiving a magnetic field signal from a magnetic field transducer, the magnetic field signal proportional to sensed magnetic fields associated with magnetic field sources, in a processor, processing the magnetic field signal to determine magnetic field axes of rotation corresponding to rotations of the sensed magnetic fields, and using the magnetic field axes of rotation to render a position of the magnetic field transducer.