Abstract: In locating a transmitter, a central processor calculates a matched filter detector output for each of one or more candidate transmitter locations by applying a linear filter to low frequency magnetic field measurements obtained at a plurality of receiver locations. The central processor then determines the location of the transmitter based on the one or more calculated matched filter detector outputs. The linear filter is derived for the one or more candidate transmitter locations.

Abstract: In locating a transmitter, a central processor calculates a matched filter detector output for each of one or more candidate transmitter locations by applying a linear filter to low frequency magnetic field measurements obtained at a plurality of receiver locations. The central processor then determines the location of the transmitter based on the one or more calculated matched filter detector outputs.

Abstract: An apparatus for measuring volatile organic compounds in a gas includes a sensor chamber having a housing with a gas inlet, a gas outlet, and a gas flow path from the gas inlet to the gas outlet, a set of baffles within the housing and positioned in the gas flow path, and a set of sensors within the housing and positioned in the gas flow path. Each sensor has an electrically conductive polymer whose electrical properties are dependent upon the presence of specific volatile organic compounds in the gas flow. Desirably, the set of baffles and the set of sensors are cooperatively positioned such that the time for gas to flow from the gas inlet to each of the sensors is substantially the same. The apparatus further includes a pump that removes the gas from the gas outlet of the housing, and an electronic circuit that measures the electrical properties of each of the sensors.

Abstract: Methods including a Kalman filter tracking method for localizing a magnetic field source and which employs a linear perturbation method. The linear perturbation method linearizes an objective function in the neighborhood of the actual source enabling the source location to be computed in a single operation. Successive applications of the linear perturbation method lead to successive improvements in the localization result.

Abstract: A magnetic object tracking algorithm, that may be implemented as an apparatus or a method, that permits kinematic tracking of magnetized objects, or targets, using magnetic field strength measurements derived from one or more vector magnetometers. The magnetic object tracking algorithm effectively tracks a maneuvering magnetic dipole target using an extended Kalman filter directly observing (processing) real magnetic field strength data.

Abstract: A target's magnetic dipole includes both a permanent component and an induced component that is caused by the interaction of the target at a given heading with the ambient magnetic field. In order to accurately classify targets, a library of characterization matrices is built for a plurality of candidate targets. The matrices characterize what the magnetic dipoles would be in a given ambient magnetic field at a particular heading. In practice, some localization algorithm is used to provide a target's magnetic dipole and heading. Magnetic dipoles for each of the candidate targets are predicted using the target's heading, the ambient magnetic field, and the characterization matrices. The target is then classified as the candidate target(s) providing the best match to the target's measured magnetic dipole.

Abstract: A processing method and apparatus that process magnetometer data derived from an array of magnetometer sensors and outputs the position or location of a magnetic dipole. In the method and apparatus, (a) a set of actual magnetic field measurements of a magnetic dipole is collected using the array of magnetic sensors. Then (b), a location for the magnetic dipole is hypothesized. Then (c), a set of estimated magnetic field measurements is determined that would be formed by a magnetic dipole at the hypothesized location. Then (d), the actual magnetic field measurements are compared with the estimated magnetic field measurements. Steps (b) through (d) are repeated for all hypothesized locations within the detection range of the array of magnetic sensors. The position or location of the dipole is displayed for viewing on a display.