Positioning system and method

• US 20080036652A1
• Filed: 12/18/2006
• Published: 02/14/2008
• Est. Priority Date: 12/16/2005
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon UTD, Inc. (Rtx Corporation)
• Inventors: Dolgin, Benjamin, Cotten, Steven, Shore, Michael
• Granted Patent: US 8,018,382 B2
• Time in Patent Office: Days
• US Class Current: 342/357.06
• 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 vector values of a magnetic field produced by the beacons;

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

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

at least one unit that displays navigation information to an operator.

2. The positioning system according to claim 1 wherein the algorithm comprises measurements of the local Earth magnetic field vector and direction of gravity to improve navigation accuracy.

3. The positioning system according to claim 1 wherein the algorithm comprises additional signals of opportunity from transmitters in the very low/low/medium frequency range and AM radio signals to improve navigation accuracy.

4. The positioning system according to claim 1 wherein the algorithm comprises signals from an inertial navigation system, atmospheric pressure altimeters, and odometers that measure a total distance traveled to improve navigation accuracy.

5. 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 to improve navigation accuracy.

6. The positioning system according to claim 1 wherein the algorithm comprises signals from multiple sources to improve navigation accuracy.

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

8. The positioning system according to claim 7 wherein the electromagnetic beacons can measure their own position and orientation in an external coordinate system and communicate that information to the computing devices that implement the navigation algorithm to transform the spatial magnetic field distribution into the spatial distribution with respect to the external coordinate system.

9. The positioning system according to claim 7 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 computing devices that implement the navigation algorithm to transform the spatial distribution of magnetic field into a spatial distribution with respect to the external coordinate system.

10. The positioning system according to claim 7 wherein the electromagnetic beacons that control an emitted electromagnetic field by reference to an internal clock and can synchronize the internal clocks with each other and with an internal clock of the magnetic field sensor and/or the data acquisition system(s).

11. The positioning system according to claim 10 wherein the beacons that synchronize the internal clocks, with respect to any signal of opportunity, before deployment in a field and maintain synchronization by maintaining accuracy of the clocks.

12. The positioning system according to claim 10 comprising the beacons and the data acquisition systems that synchronize the internal clocks using the very low frequency signals generated by the beacons or by other cooperative sources.

13. The positioning system according to claim 10 comprising the beacons that radiate signals at exactly a same or fractional frequency, such as beacon frequency ratios of 1:

1, 1;

2, 2;

3, and 3;

4.

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

15. The positioning system according to claim 14 comprises the processing algorithm that 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 the magnetic compass.

16. The positioning system according to claim 14 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.

17. The positioning system according to claim 14 wherein the processing algorithm characterizes the local magnetic anomalies by comparing true geographic East-West as measured by a gyro compass and the magnetic “

East”

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

18. The positioning system according to claim 17 wherein the artificial magnetic dipole is formed by two or more synchronized beacons placed in a near horizontal orientation near a navigation site that are separated by a relatively large distance and are oriented in a direction that is not parallel to North-South.

19. The positioning system according to claim 14 wherein the processing algorithm that characterizes local magnetic anomalies by comparing directions of the magnetic fields produced by the navigation beacons and measured by the magnetic field sensor vs. 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.

20. The positioning system according to claim 14 wherein the processing algorithm determines local magnetic anomalies by measuring the magnetic field at multiple positions with known geographic coordinates above or below ground.

21. The positioning system according to claim 20 wherein the processing algorithm where measurements are performed above ground so that the positions may be measured independently with respect to a GPS or a similar navigational system.

22. The positioning system according to claim 20 wherein characterization of magnetic anomalies performed using one magnetic field sensor associated with the data acquisition and computing system but the characterization so derived is used by all magnetic field sensors with their data acquisition systems and their computing devices and displays.

23. The positioning system according to claim 1 wherein the beacons of claim 13 that change their frequencies in a predetermined manner to form temporary artificial beacons.

24. The positioning system according to claim 13 wherein the beacons transmit at 2 or more frequencies such that one of these signals forms the artificial dipoles while the other frequencies do not but form a beat frequency signal.

25. The positioning system according to claim 10 wherein the data acquisition 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.

26. The positioning system according to claim 25 wherein the synchronous detection comprises the signal generated by the beacons has fractional frequency ratios.

27. The positioning system according to claim 25 comprises the synchronous detection where each of the frequencies of all the beacons changes in a pre-determined pseudo-random manner.

28. The positioning system according to claim 25 comprises the synchronous detection of where some of the beacons transmit at several frequencies simultaneously.

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

30. The positioning system according to claim 1 wherein the magnetic field sensor is based on a coiled antenna comprising at least 3 wire coils with orientations that are not parallel to a single plane.

31. The positioning system according to claim 1 wherein the magnetic field sensor is based on 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, and a superconducting quantum interference device magnetometer.

32. The positioning system according to claim 31 wherein the ferrite magnetic antenna is formed by an oblong piece of high magnetic permeability material with a high length-to-diameter ratio.

33. The positioning system according to claim 7 wherein the beacons communicate information unrelated to navigation to navigation devices.

34. The positioning system according to claim 33 wherein the communication system uses harmonics or sub-harmonics frequencies, wherein the use of the frequencies facilitates synchronous detection, of the beacon system to communicate information unrelated to navigation of the navigation devices.

35. The positioning system according to claim 14 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.

36. The positioning system according to claim 14 wherein the navigation system has an ability to measure an electromagnetic radiation at frequencies other than those used for navigation that may be initiated by other sources.

37. The positioning system according to claim 36 wherein the navigation system combines the navigation data and the non-navigation electromagnetic data to determine the geological and hydrological characteristics of media and characteristics of man-made structures surrounding the magnetic field sensor.

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

39. The positioning system according to claim 38 wherein the navigation system uses the electromagnetic signal in multiple spectral regions for navigation and characterization of a subsurface geophysical environment.

40. The positioning system according to claim 35 wherein the navigation system algorithm uses the beacon of claim 8 with known locations to characterize other RF sources.

41. The positioning system according to claim 30 wherein the navigation system uses at least one coil of the coil antenna to transmit information to a surface.

42. The positioning system according to claim 41 wherein the navigation system uses the beacons as receivers for the signal transmitted by the coil antenna.

43. The positioning system according to claim 7 wherein the beacon comprises the coil wrapped around a ferromagnetic sphere and a digitally controlled electronics with a synchronized clock is designed to introduce a current into the coil.

44. The positioning system according to claim 43 wherein the coil that is placed either around a largest cross-section of a sphere, or uniformly around the sphere, or some intermediate partial coverage of the sphere.

45. The positioning system according to claim 7 wherein the algorithm uses effects of known geological and hydrological features to improve navigation accuracy.

46. The positioning system according to claim 45 wherein the algorithm can optimize a location of the beacons for best navigation results.

47. The positioning system according to claim 7 wherein the beacon can be moved in a predetermined fashion to improve a navigation and/or a geological characterization of a site.

48. The positioning system according to claim 7 wherein the beacon can scan a space in a predetermined fashion to improve a navigation and/or a geological characterization of a site, the scan being a C-scan or conical scan.

49. The positioning system according to claim 7 wherein a delivery and a placement of the beacon using hand placement, parachutes, and penetrometers, the penetrometers being a delivery system comprising a large diameter penetrometers that enclose the whole of the beacon and a small diameter penetrometer that are attached to the beacon and are used as a mount.

50. The positioning system according to claim 48 wherein the beacons are located aboard stationary and moving vehicles, helicopters, and drones.