GNSS ULTRA-SHORT BASELINE HEADING DETERMINATION SYSTEM AND METHOD
First Claim
1. A heading determination comprising:
- an inertial measurement unit (IMU) adapted for detecting a magnitude and a direction of movement of the system about an axis of rotation and providing an output signal corresponding to said movement magnitude and direction;
at least two GNSS receivers each providing an output comprising GNSS ranging signals;
at least two GNSS antennas each attached to a respective GNSS receiver;
each GNSS antenna having a baseline separation from every other GNSS antenna that is no more than 0.5 meters; and
a processor connected to said IMU and said receivers, wherein the processor receives output data from the IMU and GNSS receivers and uses said output data to calculate a heading of the heading determination system.
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Accused Products
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.
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Citations
21 Claims
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1. A heading determination comprising:
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an inertial measurement unit (IMU) adapted for detecting a magnitude and a direction of movement of the system about an axis of rotation and providing an output signal corresponding to said movement magnitude and direction; at least two GNSS receivers each providing an output comprising GNSS ranging signals; at least two GNSS antennas each attached to a respective GNSS receiver; each GNSS antenna having a baseline separation from every other GNSS antenna that is no more than 0.5 meters; and a processor connected to said IMU and said receivers, wherein the processor receives output data from the IMU and GNSS receivers and uses said output data to calculate a heading of the heading determination system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A system for determining the heading of an entity, comprising:
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an inertial measurement unit (IMU) adapted for detecting a magnitude and a direction of movement of the system about an axis of rotation and providing an output signal corresponding to said movement magnitude and direction; at least two GNSS receivers each providing an output comprising GNSS ranging signals; at least two GNSS antennas each attached to a respective GNSS receiver; each GNSS antenna having a baseline separation from every other GNSS antenna that is no more than 0.5 meters; a processor connected to said IMU and said receivers, wherein the processor receives output data from the IMU and GNSS receivers and uses said output data to calculate a heading of the heading determination system; a data recorder, wherein the data recorder is capable of storing the data received by and calculated by the heading determination system for eventual retrieval, analysis and playback; a three-phase process of defined USBL algorithms required to derive an accurate heading solution, including a preparation phase, an analysis phase, and a validation phase; said preparation phase comprising; a) timing and synchronizing data acquired from the GNSS and IMU systems to eliminate time delays and synch data; b) interpolating GNSS receiver signals based on timestamps of position recordings to allow for the data of one receiver to be interpolated off of a second receiver'"'"'s data; c) selecting the best GNSS satellites for USBL calculations to allow for the highest quality position data using an algorithm and ranking system which uses factors such as satellite elevation, recent cycle slips, satellite health, signal-to-noise ratio, and other relevant satellite quality factors; and d) determining the usability of the data obtained from the satellites based on the actual data received; said analysis phase comprising; a) determining the USBL baseline length, either from hard-coded data or using pre-programmed algorithms based on the physical components allowing for a flexible USBL baseline length; b) compensating for tilt effects using data received from the inertial measurement unit to determine the pitch and roll of the system and applying this information to positional equations for precise position determination; c) resolving the integer ambiguity inhering in a USBL GNSS system with multiple antennas; and d) determining the heading of the mobile entity using double difference phase measurements, baseline length, and satellite elevations and azimuths; said validation phase comprising; a) comparing the new solution to historic data to check whether the determined heading is reasonable; b) cross-comparing redundant data sources using other sources such as magnetic compasses or other secondary positioning systems; and c) final validation of the solution. - View Dependent Claims (13, 14)
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15. A method for determining a navigational heading comprising the steps of:
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placing at least two GNSS receivers on an object; connecting a GNSS antenna to each GNSS receiver; mounting each GNSS antenna to the object such that each GNSS antenna is separated from every other GNSS antenna by a distance not to exceed 0.5 meters; placing an inertial measurement unit (IMU) on the object; and placing a processor on the object, wherein the processor calculates the difference in phase of a GNSS satellite signal as it was received by at least two GTNSS receivers, wherein the processor combines the calculated phase difference with data received from the IMU to determine the heading of the object. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A method for determining a navigational heading comprising the steps of:
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placing at least two GNSS receivers on an object; connecting a GNSS antenna to each GNSS receiver; mounting each GNSS antenna to the object such that each GNSS antenna is separated from every other GNSS antenna by a distance not to exceed 0.5 meters; placing an inertial measurement unit (IMU) on the object; placing a processor on the object, wherein the processor calculates the difference in phase of a GNSS satellite signal as it was received by at least two GNSS receivers, wherein the processor combines the calculated phase difference with data received from the IMU to determine the heading of the object; following three major phases of defined USBL algorithms required to derive an accurate heading solution, including a preparation phase, an analysis phase, and a validation phase; said preparation further comprising a first step of timing and synchronizing data acquired from the GNSS and IMU systems to eliminate time delays and synch data, a second step of interpolating GNSS receiver signals based on timestamps of position recordings to allow for the data of one receiver to be interpolated off of a second receiver'"'"'s data, a third step of selecting the best GNSS satellites for USBL calculations to allow for the highest quality position data using an algorithm and ranking system which uses factors such as satellite elevation, recent cycle slips, satellite health, signal-to-noise ratio, and other relevant satellite quality factors, and a fourth step of determining the usability of the data obtained from the satellites based on the actual data received; said analysis phase further comprising a first step of determining the USBL baseline length, either from hard-coded data or using pre-programmed algorithms based on the physical components allowing for a flexible USBL baseline length, a second step of compensating for tilt effects using data received from the inertial measurement unit to determine the pitch and roll of the system and applying this information to positional equations for precise position determination, a third step of resolving the integer ambiguity inhering in a USBL GNSS system with multiple antennas, and a fourth step of determining the heading of the mobile entity using double difference phase measurements, baseline length, and satellite elevations and azimuths; and said validation phase further comprising a first step of comparing the new solution to historic data to check whether the determined heading is reasonable, a second step of cross-comparing redundant data sources using other sources such as magnetic compasses or other secondary positioning systems, and a third step of final validation of the solution.
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Specification