Positioning system and method

• US 8,018,382 B2
• Filed: 12/18/2006
• Issued: 09/13/2011
• Est. Priority Date: 12/16/2005
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon UTD, Inc. (Rtx Corporation)
• Inventors: Shore, Michael, Cotten, Steven, Dolgin, Benjamin
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Nguyen; Nga X
• Application Number:
  US11/640,337
• Publication Number:
  US 20080036652A1
• Time in Patent Office: 1,730 Days
• Field of Search: 342385-386, 342/464, 342/459, 342/455, 342/462
• US Class Current: 342/386
• CPC Class Codes: E21B 47/0232 at least one of the energy sources or one of the detectors being located on or above the ground surface
• CPC Class Codes: G01C 15/00 Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00

Abstract

A positioning system designed to provide a three dimensional location of an object. The system can include one or more multiple transmitters or electromagnetic beacons, software defined radio receivers with an associated processing unit and data acquisition system, and magnetic antennas. The system applies theoretical calculations, scale model testing, signal processing, and sensor data to operate.

Claims

1. A positioning system comprising:

at least two electromagnetic beacons;

a sensor that measures instantaneous values of magnetic vectors of a magnetic field produced by the beacons, said magnetic vectors having orientations;

a processing algorithm that calculates a position of the sensor based, on the values and said orientations of the magnetic vectors;

at least one data acquisition and computing system that implements the algorithm; and

at least one unit that displays navigation information to an operator; and

wherein the electromagnetic beacons are located above ground, and wherein the sensor that measures the instantaneous vector values of the magnetic field produced by the electromagnetic beacons is located below the ground, and wherein the unit that displays the navigation information to the operator is located below the ground, such that the navigation information is displayed to the operator below the ground while the operator is located below the ground and while the beacons are located above the ground.

2. The positioning system according to claim 1 wherein the positioning system measures the local Earth magnetic field vector and direction of gravity.

3. The positioning system according to claim 1 wherein the positioning system receives signals of opportunity from transmitters in the very low/low/medium frequency range.

4. The positioning system according to claim 1 wherein the algorithm comprises signals from a network of transceivers placed between a navigation system and a location where a reference to an external navigation system exists.

5. The positioning system according to claim 1 wherein the electromagnetic beacons include magnetic coils with or without a ferromagnetic core that have a well characterized spatial distribution of the magnetic field.

6. The positioning system according to claim 5 wherein the electromagnetic beacons can measure their own position and orientation in an external coordinate system and communicate that information to the data acquisition and computing system to transform the spatial magnetic field distribution into a spatial distribution with respect to an external coordinate system.

7. The positioning system according to claim 5 wherein the electromagnetic beacons can measure their position and physically change their orientation in space and thus change the orientation of their magnetic field in an external coordinate system and communicate that information to the data acquisition and computing system to transform the spatial distribution into a spatial distribution with respect to the external coordinate system.

8. The positioning system according to claim 5 wherein the electromagnetic beacons control an emitted electromagnetic field by reference to an internal clock and can synchronize internal clocks with each other and with an internal clock of the magnetic field sensor and/or the data acquisition and computing system.

9. The positioning system according to claim 8 wherein the beacons synchronize internal clocks, with respect to a signal of opportunity, before deployment in a field and maintain synchronization by maintaining clock accuracy.

10. The positioning system according to claim 1 wherein the processing algorithm improves navigational data accuracy by correcting for local magnetic anomalies.

11. The positioning system according to claim 10 wherein the processing algorithm characterizes the local magnetic anomalies by comparing true geographic North-South direction as measured by a gyro compass with the magnetic North as measured by a magnetic compass.

12. The positioning system according to claim 10 wherein the processing algorithm characterizes the local magnetic anomalies by comparing true vertical direction as measured by an inclinometer and an electromagnetic vertical as measured by a direction of propagation of a plane electromagnetic wave from a cooperative source.

13. The positioning system according to claim 10 wherein the processing algorithm characterizes the local magnetic anomalies by comparing true geographic East-West as measured by a gyro compass and magnetic “

East”

created by an artificial magnetic dipole placed near a navigation site.

14. The positioning system according to claim 13 wherein the artificial magnetic dipole is formed by two or more synchronized beacons that are placed in a near horizontal orientation near the navigation site, and that are separated by a relatively large distance and are oriented in a direction that is not parallel to North-South.

15. The positioning system according to claim 10 wherein the processing algorithm characterizes local magnetic anomalies by comparing directions of the magnetic fields produced by the beacons and measured by the magnetic field sensor to actual coordinates of the magnetic field sensor as measured by other devices such as a GPS when the magnetic field sensor is above ground, or by positioning the magnetic field sensor over known landmarks or other triangulated points.

16. The positioning system according to claim 10 wherein the processing algorithm determines local magnetic anomalies by measuring magnetic fields at multiple positions with known geographic coordinates above or below ground.

17. The positioning system according to claim 16 wherein the measurements are performed above ground so that the positions may be measured independently with respect to a GPS or a similar navigational system.

18. The positioning system according to claim 16 wherein characterization of magnetic anomalies is performed using one magnetic field sensor and the characterization so derived is used by other magnetic field sensors and displays.

19. The positioning system according to claim 1 wherein the beacons change their frequencies in a predetermined manner to form temporary artificial beacons.

20. The positioning system according to claim 1 wherein the beacons transmit at 2 or more frequencies such that one of these signals forms artificial dipoles while the other frequencies form a beat frequency signal.

21. The positioning system according to claim 8 wherein the data acquisition and computing system performs synchronous detection of signals from the beacons, the synchronous detection occurring where the measured signal received by the magnetic field sensor is correlated with an expected time dependent profile of the signal that is generated based on a synchronization clock, the detection being performed by maximizing in-phase signals and minimizing out-of-phase and random signals.

22. The positioning system according to claim 21 wherein a signal generated by the beacons has fractional frequency ratios.

23. The positioning system according to claim 21 wherein each of the frequencies of all the beacons changes in a predetermined pseudo-random manner.

24. The positioning system according to claim 21 wherein some of the beacons transmit at several frequencies simultaneously.

25. The positioning system according to claim 1 where beacon signals are modulated to transmit information to display units.

26. The positioning system according to claim 1 wherein the magnetic field sensor includes a coil antenna comprising at least 3 wire coils with orientations that are not parallel to a single plane.

27. The positioning system according to claim 1 wherein the magnetic field sensor includes a ferrite magnetic antenna placed in a proximity of a magnetic field sensing element, such as a coil, a fluxgate, a magnetoresistor, a Hall effect sensor, or a superconducting quantum interference device magnetometer.

28. The positioning system according to claim 27 wherein the ferrite magnetic antenna is formed by an oblong piece of high magnetic permeability material with a high length-to-diameter ratio.

29. The positioning system according to claim 5 wherein the beacons communicate information to navigation devices, and wherein the communicated information is unrelated to navigation.

30. The positioning system according to claim 29 wherein a communication system uses harmonics or sub-harmonics frequencies, and wherein the use of the frequencies facilitates synchronous detection.

31. The positioning system according to claim 10 wherein the algorithm uses magnetic anomalies to determine the geological and hydrological characteristics of media and characteristics of man-made structures surrounding the magnetic field sensor.

32. The positioning system according to claim 10 wherein the positioning system has an ability to measure electromagnetic radiation at frequencies other than those used for navigation that may be initiated by other sources.

33. The positioning system according to claim 32 wherein the positioning system combines navigation data and non-navigation electromagnetic data to determine the geological and hydrological characteristics of media and characteristics of man-made structures surrounding the magnetic field sensor.

34. The positioning system according to claim 1 wherein the beacons transmit electromagnetic radiation that is used for geological and hydrological characterization.

35. The positioning system according to claim 34 wherein an electromagnetic signal is used in multiple spectral regions for navigation and characterization of a subsurface geophysical environment.

36. The positioning system according to claim 31 wherein the electromagnetic beacons can measure their own position and orientation in an external coordinate system and communicate that information to the data acquisition and computing system to transform the spatial magnetic field distribution into a spatial distribution with respect to the external coordinate system, and wherein the algorithm uses at least one of the beacons with known locations to characterize other RF sources.

37. The positioning system according to claim 26 wherein at least one coil of the coil antenna is used to transmit information to a surface.

38. The positioning system according to claim 37 wherein the beacons are used as receivers for the signal transmitted by the coil antenna.

39. The positioning system according to claim 5 wherein a coil is wrapped around a ferromagnetic sphere and digitally controlled electronics with a synchronized clock introduce a current into the coil.

40. The positioning system according to claim 39 wherein the coil is placed either around a largest cross-section of a sphere, or uniformly around the sphere, or some intermediate partial coverage of the sphere.

41. The positioning system of claim 1, wherein the algorithm uses effects of known geological and hydrological features.

42. The positioning system according to claim 41 wherein the algorithm can optimize a location of the beacons for best navigation results.

43. The positioning system according to claim 5 wherein the beacons can be moved in a predetermined fashion.

44. The positioning system according to claim 5 wherein the positioning system can scan a space in a predetermined fashion, the scan being a C-scan or conical scan.

45. The positioning system according to claim 5 wherein a beacon is arranged to be delivered and placed by hand placement, parachute, or penetrometer, the penetrometer being a large diameter penetrometer that encloses the whole of the beacon and a small diameter penetrometer that is attached to the beacon and used as a mount.

46. The positioning system according to claim 44 wherein beacons are located aboard stationary or moving vehicles, helicopters, or drones.

47. The positioning system according to claim 1 wherein the positioning system receives AM radio signals.

48. A positioning system comprising:

at least two electromagnetic beacons;

a sensor that measures instantaneous values of magnetic vectors of a magnetic field produced by the beacons, said magnetic vectors having orientations;

a processing algorithm that calculates a position of the sensor based on the values and said orientations of the magnetic vectors;

at least one data acquisition and computing system that implements the algorithm; and

at least one unit that displays navigation information to an operator; and

wherein the positioning system receives signals, representative of elevation of the sensor, from an atmospheric pressure altimeter.

49. The positioning system according to claim 48 wherein the positioning system receives signals from an inertial navigation system and odometers that measure a total distance traveled.