Abstract: A method and system for determining a bending angle and/or the presence of atmospheric ducting. An array of antennas is used in order to form an interferometer. The interferometer receives signals from GPS satellites and uses the index of infraction in order to determine a bending angle of the GPS signals and/or the presence of atmospheric ducting.

Abstract: System and method for determining the roll rate and roll angle of a spinning platform. The IQ amplitude and/or phase characteristics of GPS signals received at a single receiver antenna are measured using the signals output directly by a correlator that is driven at the satellite tracking frequency used for forming the navigation solution. The roll rate and roll angle are determined in real time by a Roll filter, which is preferably an Extended Kalman Filter (EKF) employing probabilistic data association, whose inputs include the measured IQ characteristics and the navigation solution. Data from non-GPS measurement sources is optionally provided to update the navigation and/or roll solution.

Abstract: A system for aligning two ground-based antennae (100, 110) or a ground-based antenna (100) and a satellite antenna (110), for use in military and civilian settings, in which a visual display is generated showing a graphical representation of the antennae including graphical representations indicating both the axis of the main lobe (102) and the approximate radiation pattern (414) of the antennae, superimposed over a live imaging of the local terrain. The alignment is achieved when the graphical representations of the main axis and radiation patterns of the two antennae align with each other.

Abstract: A microprocessor controlled security tag and accompanying security system is described. The tag generally includes a housing having external contacts to interface with elongated contacts on a connecting band. The band forms a complex impedance circuit with a patient's limb that allows detection features such as removal and band compromise. A microprocessor and related circuitry as well as a transmitter and receivers are enclosed in the housing. The tag is adapted to communicate inductively with an activator/deactivator unit as well as a tag programmer that updates and changes tag features in the tag firmware. The overall system further includes a hub to receive the data from a plurality of tags in the system. The tag can also communicate with a phased multiple antenna that sends signals to the tag.

Abstract: A system for accurately directing a directional antenna, that includes a calibration system for finding the current azimuth of the antenna and a rotation sensor attached to the antenna, for measuring deviations from the current azimuth of the antenna.

Abstract: An exemplary radio-based navigation system uses a small multimode direction-finding antenna and a direction-finding receiver capable of determining platform position, velocity, attitude, and time while simultaneously providing protection against narrowband and broadband sources of interference. Global Navigation Satellite System (GNSS) signals such as those from the Global Positioning System (GPS) provide attitude measurements with a compact multimode direction-finding antenna (e.g., a small two-arm spiral with improved angle-of-arrival performance over the entire hemisphere enhanced through the use of a conductive vertical extension of the antenna ground plane about the antenna perimeter and/or conductive posts placed evenly around the antenna perimeter) which provides simultaneous protection against jammers. The multimode spiral may be treated as an array of rotationally-symmetric antenna elements.

Abstract: A system and method for determining the roll rate and roll angle of a spinning platform by using the measured phase and/or amplitude differences between the GPS satellite signals received on two or more antennas. The measured signal differences and the navigation solution from a GPS receiver are processed in a roll filter to obtain the desired information. Data from non-GPS measurement sources is optionally provided to update the navigation solution. Although of wide applicability, the invention is uniquely suited to the measurement of roll rates and roll angles of fast spinning platforms with small baselines in the presence as well as in the absence of jamming, and where the antennas are separated from each other by distances that are a fraction of the GPS signal wavelength.

Abstract: Apparatus and methods determine the rotational position of a spinning object. A satellite positioning system can be used to determine the spatial position of an object, which in turn can be used to guide the object. However, when the object is spinning, such as an artillery shell, then the rotational orientation should be known in order to properly actuate the control surfaces, such as fins, which will also be spinning.

Abstract: A portable DGPS navigation apparatus is provided. The apparatus includes a receiver assembly and a DGPS antenna assembly. The receiver assembly includes a GNSS antenna, a GNSS receiver, and a DGPS modem. The DGPS antenna assembly includes a DGPS antenna; a top connector for coupling the DGPS antenna assembly to the receiver assembly such that the receiver assembly and DGPS antenna assembly are aligned with a geodetic pole, and a bottom connecter.

Abstract: A system and method for determining the roll rate and roll angle of a spinning platform by using the measured phase and/or amplitude differences between the GPS satellite signals received on two or more antennas. The measured signal differences and the navigation solution from a GPS receiver are processed in a roll filter to obtain the desired information. Data from non-GPS measurement sources is optionally provided to update the navigation solution. Although of wide applicability, the invention is uniquely suited to the measurement of roll rates and roll angles of fast spinning platforms with small baselines in the presence as well as in the absence of jamming, and where the antennas are separated from each other by distances that are a fraction of the GPS signal wavelength.

Abstract: A multi-antenna GNSS system and method provide earth-referenced GNSS heading and position solutions. The system and method compensate for partial blocking of the antennas by using a known attitude or orientation of the structure, which can be determined by an orientation device or with GNSS measurements. Multiple receiver units can optionally be provided and can share a common clock signal for processing multiple GNSS signals in unison. The system can optionally be installed on fixed or slow-moving structures, such as dams and marine vessels, and on mobile structures such as terrestrial vehicles and aircraft.

Abstract: A heading determination system comprises an inertial measurement unit (IMU) coupled with at least two GNSS receivers, each receiver paired with and receiving signals from a corresponding GNSS antenna, wherein the GNSS antennas are separated by an ultra-short baseline. The heading determination system receives signals broadcast by a plurality of GNSS satellites and calculates the phase difference in the signal seen among the separate GNSS antennas. Using this phase difference information, derived from comparing the signals received from a plurality of GNSS satellites, along with attitude data generated by the IMU, the heading determination system calculates a highly-accurate heading solution. A method is provided for determining a heading of a system including an IMU coupled with at least two GNSS receivers, with each receiver being paired with and receiving signals from a corresponding GNSS antenna and the antennas being separated by an ultra-short baseline.

Abstract: A system and method for determining the roll rate and roll angle of a spinning platform in a jamming environment, by suppressing the interference signals from the received GPS signals and using the measured phase and amplitude differences between the GPS satellite signals received on two or more antennas. The measured signal differences and the navigation solution from a GPS receiver are processed in a roll filter to obtain the desired information. Data from non-GPS measurement sources is optionally provided to update the navigation solution. Although of wide applicability, the invention is uniquely suited to the measurement of roll rates and roll angles of fast spinning platforms with small baselines in the presence of jamming, and where the antennas are separated from each other by distances that are a fraction of the GPS signal wavelength.

Abstract: Apparatus and methods determine the rotational position of a spinning object. A satellite positioning system can be used to determine the spatial position of an object, which in turn can be used to guide the object. However, when the object is spinning, such as an artillery shell, then the rotational orientation should be known in order to properly actuate the control surfaces, such as fins, which will also be spinning.

Abstract: A system and method for automatically calibrating the aiming direction of a camera onboard a vehicle. The method uses GPS and solar almanac data to estimate the location of the sun relative to the vehicle, and compares this to the solar position in an image from the camera. The comparison is performed with an ongoing recursive calculation which yields an improved estimate of the sun position relative to the vehicle, while simultaneously calibrating the aiming direction of the camera. The aiming calibration data is used to improve the accuracy of the camera's images as used for all of the camera's other functions.

Abstract: A system for generating and utilizing a look-up mechanism consisting of one or more phase difference error maps, tables and/or mathematical models calculates the respective maps, tables and/or models by placing a short baseline or ultra-short baseline antenna array in a known location and known orientation, determining angles of incidence of incoming GNSS satellite signals with respect the antenna array and calculating expected carrier phase differences between respective pairs of antennas, calculating measured carrier phase differences between the respective pairs of antennas, and determining carrier phase difference errors using the expected and measured carrier phase differences. The carrier phase difference errors are then recorded in the look-up mechanism, with the maps and, as appropriate, look-up tables for the respective pairs of antennas being indexed by angles of incidence. Thereafter, the system utilizes the look-up mechanism when determining the unknown orientation of the antenna structure.

Abstract: A heading determination system comprises an inertial measurement unit (IMU) coupled with at least two GNSS receivers, each receiver paired with and receiving signals from a corresponding GNSS antenna, wherein the GNSS antennas are separated by an ultra-short baseline. The heading determination system receives signals broadcast by a plurality of GNSS satellites and calculates the phase difference in the signal seen among the separate GNSS antennas. Using this phase difference information, derived from comparing the signals received from a plurality of GNSS satellites, along with attitude data generated by the IMU, the heading determination system calculates a highly-accurate heading solution. A method is provided for determining a heading of a system including an IMU coupled with at least two GNSS receivers, with each receiver being paired with and receiving signals from a corresponding GNSS antenna and the antennas being separated by an ultra-short baseline.

Abstract: A reception environment is determined to be a multipath environment when the difference (positioning altitude difference) between the maximum value (maximum altitude) and the minimum value (minimum altitude) of the altitudes of candidate present positions P of respective satellite sets exceeds a given threshold value (e.g., 200 m), and is determined to be an open-sky environment when the positioning altitude difference is equal to or less than the given threshold value. When the reception environment is the open-sky environment, an evaluation point E of each satellite set is calculated using a known evaluation method based on the number of satellites, a PDOP value, and the like.

Abstract: A method and an apparatus for estimating behaviors of a vehicle are provided. At least two GPS antennas are located along a longitudinal axis of a vehicle so that speed vectors at the positions where the GPS antennas are located can be determined based on GPS signals received by the GPS antennas. The speed vectors are known to be estimated with high accuracy based on the GPS signals. The positions of the GPS antennas on the local coordinate system are estimated based on such highly accurate speed vectors, so that the estimated positions may also have high accuracy. Based on a line connecting these highly accurate positions of the GPS antennas, an inclination of the longitudinal axis of the vehicle is estimated. Use of the high-accuracy speed vectors enables high-accuracy estimation on the positions of the GPS antennas and the vehicle direction on the local coordinate system.

Abstract: An apparatus for initializing a wellbore survey tool comprises a base portion and a first mounting portion mechanically coupled to the base portion. The first mounting portion can be adapted to be mechanically coupled to at least one directional reference system configured to provide data indicative of an orientation of the at least one directional reference system with respect to a reference direction. The apparatus of certain embodiments further comprises a second mounting portion mechanically coupled to the base portion, the second mounting portion configured to be mechanically coupled to a wellbore survey tool such that the wellbore survey tool has a predetermined orientation with respect to the at least one directional reference system.

Abstract: A system and method for determining the roll rate and roll angle of a spinning platform in a jamming environment, by suppressing the interference signals from the received GPS signals and using the measured phase and amplitude differences between the GPS satellite signals received on two or more antennas. The measured signal differences and the navigation solution from a GPS receiver are processed in a roll filter to obtain the desired information. Data from non-GPS measurement sources is optionally provided to update the navigation solution. Although of wide applicability, the invention is uniquely suited to the measurement of roll rates and roll angles of fast spinning platforms with small baselines in the presence of jamming, and where the antennas are separated from each other by distances that are a fraction of the GPS signal wavelength.

Abstract: A method for determining the attitude of a stabilized platform having three or more antennae includes, for each antenna, front-end processing a GPS signal received, the front-end processing including down-converting a GPS source signal by heterodyning and direct sampling, then sampling the down-converted signal. For each antenna the GPS signal is acquired by faster-than-real-time correlating the down-converted signal with each of a number of stored codes and correlating with each of a number of Doppler frequencies. The correlation is repeated for a smaller range of Doppler frequencies, and for smaller intervals of code phases. The down converted signal is then stripped of its codes, and the phases of the resulting signals from each antenna are subtracted, providing the phase differences between antennas, which are converted into attitude angles.