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A system and method for determining a position of a remote object comprising inertial sensors and three axis magnetic sensor, together with a target sighting device aligned with the observation platform to determine a target line of sight and a target range finder to determine a distance to the targ

A system and method for determining a position of a remote object comprising inertial sensors and three axis magnetic sensor, together with a target sighting device aligned with the observation platform to determine a target line of sight and a target range finder to determine a distance to the target along the line of sight. A GPS receiver may be included for determining an observation platform position and orientation, The three axis magnetic sensor provides both magnetic north and vertical attitude information for improved rapid initialization and operation in motion. Magnetic anomaly information is detected by comparing IMU and magnetic navigation information and by other methods. Target identification may be determined by a human operator and/or by computer. The system may be integrated with a weapon system to use weapon system sights. The system may be networked to provide target location and/or location error information to another identical unit or a command information system.

대표청구항 ▼

1. A system for determining a position of a target comprising: (a) an inertial measurement unit, said inertial measurement unit comprising: a triad of rate gyros mounted to a reference platform, each gyro of said triad of rage gyros having a respective rotational sensing axis; anda triad of accelero

1. A system for determining a position of a target comprising: (a) an inertial measurement unit, said inertial measurement unit comprising: a triad of rate gyros mounted to a reference platform, each gyro of said triad of rage gyros having a respective rotational sensing axis; anda triad of accelerometers mounted to said reference platform;(b) a three-axis magnetic sensor mounted to said reference platform for sensing the earth's magnetic field;(c) a position source for determining a coordinate position of the reference platform;(d) a target sighting device, said target sighting device aligned with said inertial measurement unit and said three-axis magnetic sensor, said target sighting device for finding angle coordinates defining a line from said reference platform to said target;(e) a target distance determination device for determining target distance from said reference platform along said angle coordinates; and(f) a state estimation processor for combining data from the triad of rate gyros and the triad of accelerometers with data from the three axis magnetic sensor to generate platform attitude information; said state estimation processor utilizing three axes of said three axis magnetic sensor to correct errors in said platform attitude information;wherein said position of said target is computed based on said coordinate position of the reference platform summed with a position vector having a length according to said target distance determination device and said position vector having a vector direction in accordance with said angle coordinates defining said line from said platform to said target, said angle coordinates in accordance with said platform attitude information. 2. The system of claim 1, wherein gyro bias for at least on gyro of said triad of rate gyros is corrected based on said data from said three axis magnetic sensor. 3. The system of claim 1, wherein a bias for at least one gyro of said triad of rate gyros is corrected based on a three axis measurement of the earth's magnetic vector by the three axis magnetic sensor, said correction in accordance with the observability of each gyro rotation sensing axis relative to the three-axis measurement of the earth's magnetic vector. 4. The system of claim 1, wherein magnetic information is ignored upon detecting a magnetic anomaly. 5. The system of claim 4, wherein the magnetic anomaly is determined by detecting a change in the magnitude of the earth's magnetic field over an interval of time. 6. The system of claim 4, wherein the magnetic anomaly is determined by detecting a change over an interval of time in the direction of a sensed magnetic field vector as transformed to a navigation frame. 7. The system of claim 1, wherein the target distance measuring device is a passive distance measuring device. 8. The system of claim 1, wherein the range measuring device is an active distance measuring device comprising a laser range finder or a radar range finder. 9. The system of claim 8, further including an operator input to signal when optical aiming system is observed being superimposed on a target to start a target position measurement process. 10. The system of claim 1, further including a computer video based target observation device running a target recognition process to identify the target and provide target location information relative to the video frame, and the system includes said target location information relative to the video frame do determine target location in map coordinates. 11. The system of claim 10, further including a target tracking process to track the target after the target is identified. 12. A method for determining a position of a target comprising providing a target position measurement system having a computer embedded therein performing the steps of: determining the location coordinates of an observation position;determining an attitude estimate of a system reference platform at said observation position, said attitude estimate including an azimuth estimate and a vertical attitude estimate;said determining said attitude estimate performed with reference to:a three-axis rate gyro triad sensing body motion of said reference platform,a three-axis accelerometer triad sensing the earth's gravity vector and sensing body motion of said reference platform,a GPS receiver providing position and velocity information of said reference platform, anda three-axis magnetic sensor mounted to said reference platform for sensing the earth's magnetic field, said determining said attitude estimate including the step of correcting said vertical attitude estimate based on said three-axis magnetic sensor;said target position measurement system further performing the steps of:determining a line of sight direction from said reference platform to said target, said line of sight direction including angle coordinates relative to said reference platform;determining a distance to said target along said line of sight direction; andextrapolating from said observation position along said line of sight direction by said distance to said target to determine said target position. 13. The method of claim 12, wherein the navigating step includes: correcting a bias of at least one gyro of said three-axis rate gyro triad by using a three-axis measurement of the earth's magnetic field by the three-axis magnetic sensor. 14. The method of claim 12, wherein the navigating step includes: correcting a bias for at least one gyro of said triad of rate gyros using a three-axis measurement of the earth's magnetic vector by the three-axis magnetic sensor, said correction in accordance with the observability of a gyro rotation sensing axis relative to the earth's magnetic vector measurement. 15. The method of claim 12, wherein the step of correcting said vertical attitude based on said three-axis magnetic sensor comprises the steps of: transforming a three dimensional body referenced measurement from said three-axis magnetic sensor to a navigation frame representation of the earth's magnetic vector, andcomparing said navigation frame representation of the earth's magnetic vector to a reference magnetic vector to generate a three dimensional comparison value; andcorrecting said vertical attitude estimate based on said three dimensional comparison value. 16. The method of claim 12, wherein magnetic information is ignored upon detecting a magnetic anomaly. 17. A system for determining a position of a target comprising (a) an inertial measurement unit, said inertial measurement unit comprising: a level sensor having at least two axes mounted to said reference platform;(b) a three axis magnetic sensor mounted to said reference platform for sensing the earth's magnetic field;(c) a position source for determining a coordinate position of the reference platform;(d) a target sighting device, said target sighting device aligned with said inertial measurement unit and said three axis magnetic sensor, said target sighting device for finding angle coordinates defining a line from said reference platform to the target;(e) a target distance determination device for determining target distance from said reference platform along said angle coordinates; and(f) a state estimation processor for combining data from the level sensor with data from the three axis magnetic sensor to generate platform attitude information;wherein said position of said target is computed based on said coordinate position of the reference platform summed with a position vector having a length according to said target distance determination device and said position vector having a vector direction in accordance with said angle coordinates defining said line from said platform to said target, said angle coordinates in accordance with said platform attitude information; andwherein the level sensor and three axis magnetic sensor provide redundant vertical information that cooperates to generate elevation axis information for said line from said reference platform to said target. 18. The system of claim 17, wherein the state estimation processor includes a Bayesian estimator, a Kalman estimator, a maximum likelihood estimator, or a mean square estimator. 19. The system of claim 18, further including a rate gyro triad mounted to said reference platform. 20. The system of claim 19, wherein the level sensor comprises one or more accelerometers. 21. The system of claim 20, wherein the position source means for determining the coordinate position of the reference platform comprises a GPS receiver. 22. The system of claim 21, wherein the state estimation processor is a Kalman estimator configured to estimate attitude error and an attitude residual is calculated based on a normalized vector cross product between a body referenced three axis magnetic measurement transformed to a navigation frame and a reference navigation frame magnetic vector. 23. The system of claim 22, further including a Kalman gain adjustment for observability of the attitude error based on a comparison between an uncertainty value for each magnetic axis and the measured magnitudes of the other two axes of the three axis magnetic sensor. 24. The system of claim 23, wherein the gain adjustment is provided by setting the magnetic sensor values for a Kalman measurement covariance matrix according to said comparison between said uncertainty value and said measured magnitudes.