USE OF A SKY POLARIZATION SENSOR FOR ABSOLUTE ORIENTATION DETERMINATION IN POSITION DETERMINING SYSTEMS

• US 20140022539A1
• Filed: 03/14/2013
• Published: 01/23/2014
• Est. Priority Date: 07/23/2012
• Status: Active Grant

• Current Assignee: Trimble Inc.
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: FRANCE, Peter Glen
• Granted Patent: US 9,562,764 B2
• Time in Patent Office: Days
• US Class Current: 356/139.1
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01C 15/00 Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
• CPC Class Codes: G01C 17/00 Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes using gyroscopic effect G01C19/00
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01J 4/04 Polarimeters using electric detection means G01J4/02 takes precedence
• CPC Class Codes: G01S 17/06 Systems determining position data of a target
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 19/485 whereby the further system is an optical system or imaging system
• CPC Class Codes: G01S 19/53 Determining attitude
• CPC Class Codes: G06G 7/70 for vehicles, e.g. to determine permissible loading of ships , centre of gravity, necessary fuel

Abstract

A method for determining absolute orientation of a platform is disclosed. In one embodiment, a first sky polarization data set for a first time Ti is measured using a sky polarization sensor disposed on a platform. A second sky polarization data set is obtained at a second time Tj. A difference in orientation between the first sky polarization data set and the second sky polarization data set is determined using an orientation determiner. The difference in orientation is provided as at least one orientation parameter for the platform at time Tj. The at least one orientation parameter is used to provide a direction relative to a reference point on the platform.

Claims

1. A method for determining absolute orientation of a platform, comprising:

measuring a first sky polarization data set at a first time Ti using a sky polarization sensor disposed on a platform;

obtaining a second sky polarization data set at a second time Tj;

determining a difference in orientation between said first sky polarization data set and said second sky polarization data set using an orientation determiner;

providing said difference in orientation as at least one orientation parameter for said platform at time Tj; and

using said at least one orientation parameter to provide a direction relative to a reference point on said platform.

2. The method of claim 1 further comprising:

calculating the absolute orientation of said sky polarization sensor by adding said difference in orientation.

3. The method of claim 1 further comprising:

measuring said second sky polarization data set using said sky polarization sensor on said platform.

4. The method of claim 1 further comprising:

measuring said second sky polarization data set using a second sky polarization sensor disposed in a fixed stationary mounting, said second sky polarization sensor having a known absolute orientation.

5. The method of claim 1 wherein said using said orientation determiner further comprises:

accessing a solar almanac to calculate sun azimuth and elevation as a function of location and time;

determining an estimate of the location of said platform;

calculating respective azimuth and elevation angles of the sun at times Ti and Tj;

calculating the difference in solar orientation at times Ti and Tj; and

adding said difference in solar orientation to said difference in orientation between said first sky polarization data set and said second sky polarization data set.

6. The method of claim 1 further comprising:

determining at least one orientation angle to a remote target using a visual sighting device disposed on said platform.

7. The method of claim 6 further comprising:

determining a distance to said remote target using an electronic distance measuring (EDM) system associated with said visual sighting device and disposed on said platform.

8. The method of claim 7 further comprising:

determining a location of said platform using a GNSS receiver disposed on said platform.

9. The method of claim 8 wherein said platform further comprises a support pole, said method further comprising:

using said support pole for locating a point on the ground.

10. The method of claim 7 where said EDM further comprises a total station.

11. A method for obtaining position data for a target, comprising:

orienting a visual sighting device and a sky polarization sensor toward a target wherein said visual sighting device comprises a range measurement system and is disposed in a known spatial relationship with said sky polarization sensor;

determining an absolute orientation of said visual sighting device based on a sky polarization data measurement while capturing a distance to said target from said visual sighting device;

determining a first location having a known spatial relationship to said visual sighting device; and

calculating location of said target based on said first location, said distance to said target, and said absolute orientation of said visual sighting device.

12. The method of claim 11 wherein said visual sighting device comprises an optical survey instrument.

13. The method of claim 12 further comprising:

determining said first location by a resection survey process with said optical survey instrument.

14. The method of claim 12 further comprising:

establishing said visual sighting device approximately above said first location without levelling said visual sighting device and wherein there is a known distance and orientation between said first location and said optical survey instrument.

15. The method of claim 12 further comprising:

establishing said visual sighting device vertically above said first location and levelled, and wherein there is a known distance between said first location and said optical survey instrument.

16. The method of claim 11 wherein said visual sighting device comprises an integrated electronic distance measurement (EDM) system.

17. The method of claim 11 wherein said visual sighting device comprises a camera with a display and a range measurement system.

18. The method of claim 11 further comprising:

determining said first location using a GNSS receiver.

19. The method of claim 11 wherein said visual sighting device and sky polarization sensor are integrated with a GNSS receiver in a known spatial relationship.

20. The method of claim 19 wherein said GNSS receiver, said visual sighting device and said sky polarization sensor are affixed to a pole in a known spatial relationship.

21. The method of claim 20 wherein said pole comprises said visual sighting device and said range measurement system.

22. The method of claim 11 further comprising:

using a processing system to translate said sky polarization data measurement into an orientation in a coordinate system for said visual sighting device.

23. The method of claim 22 further comprising:

translating said orientation into the WGS-84 coordinate system.

24. The method of claim 22 wherein said processing system translates said sky polarization data measurement into a local coordinate system.

25. The method of claim 22 further comprising:

receiving a sky polarization data set at a known time Ti;

accessing a sun almanac to determine azimuth and elevation angles of the sun at said time Ti and for said first location;

calculating a plurality of predicted polarization values for a plurality of respective sample points across the sky at said time Ti and for said first location;

correlating a sky polarization measurement captured using said sky polarization sensor with at least one of said plurality of predicted polarization values, and calculating the translation and rotation parameters of a transform between said sky polarization measurement and said at least one of said plurality of predicted polarization values;

converting said transform from image-space to real-world rotation parameters; and

adding said real-world rotation parameters to the azimuth and elevation angles determined from said sun almanac, to determine the yaw, pitch and roll orientation parameters for said visual sighting device.

26. The method of claim 25 further comprising:

determining at least one orientation angle to a remote target wherein said at least one orientation angle is matched to a coordinate system by a setup procedure comprising;

establishing a platform vertically over a known position;

measuring a vertical distance from said known position to said platform;

determining a level orientation for said sky polarization sensor, as determined by a bubble level; and

establishing said orientation of said platform in terms of said coordinate system by aiming said visual sighting device at a backsight point of either known azimuth or known position while measuring said sky polarization data set.

27. The method of claim 26 further comprising:

using a polarization reference station, comprising a second sky polarization sensor having measurement axes which are aligned in a known orientation with respect to True North and the local gravity vector, to generate a sky polarization reference data set; and

storing said sky polarization reference data set at a sequence of known times including said known time Ti using a first data storage system.

28. The method of claim 27 further comprising:

transmitting said sky polarization measurement from said polarization reference station to an orientation determiner coupled with said visual sighting device and said sky polarization sensor using a communications link.

29. The method of claim 28 further comprising:

transmitting said sky polarization measurement from a mobile device comprising said visual sighting device and said orientation determiner to a storage and processing system via a communications link;

sending said sky polarization reference data set from said first storage system to said storage and processing system; and

determining an orientation for said visual sighting device at said storage and processing system.

30. The method of claim 28 further comprising:

transmitting said sky polarization measurement from said orientation determiner to said polarization reference station;

processing said sky polarization measurement with reference data taken proximate to said known time Ti to bring said sky polarization measurement and said sky polarization reference data set into congruence by calculating a series of axis rotations with resultant defined angles;

using said resultant defined angles as at least one orientation parameter for said visual sighting device at time Ti; and

transmitting said resultant defined angles to said orientation determiner as the orientation parameters for the time Ti of the visual sighting system.

31. The method of claim 28 wherein said sky polarization reference data set is sent after receiving a request via said communications link from said orientation determiner for data captured proximate to time Ti.

32. The method of claim 11 wherein the sky polarization sensor comprises a photo-diode-based polarization detection system.

33. The method of claim 11 wherein the sky polarization sensor comprises a camera-based polarization detection system.

34. The method of claim 11 further comprising:

using a differential polarization process to determine said absolute orientation.

35. A method for obtaining position data for a target with a position determining device, comprising:

acquiring a first position using a total station comprising a sky polarization sensor which is disposed in a known spatial relationship to said total station;

acquiring a first orientation of said total station based on a sky polarization data set;

translating said sky polarization data set into orientation information in a coordinate system at said total station;

capturing a distance to a target using a visual sighting device of said total station comprising an internal distance measuring system; and

calculating location of said target based on said first position, said distance to target, and said orientation information.

36. A method for obtaining position data for a target with a position determining device, comprising:

using a Global Navigation Satellite System (GNSS) receiver of a position determining system to measure a first location;

using a visual sighting device, further comprising an internal distance measuring system, of said position determining system to measure a distance to a target;

using a sky polarization sensor of said position determining system to measure an orientation of said visual sighting device; and

calculating a location of said target based on said first location, said distance to said target, and said orientation of said visual sighting device.

37. A method for obtaining position data for a target, comprising:

determining a first location of a visual sighting device and a sky polarization sensing device having a known spatial relationship, from which is measured a first estimate of orientation to a target, and wherein said first estimate of orientation is based on sky polarization;

determining a second location of said visual sighting device, from which is measured a second estimate of orientation to said target, and wherein said second estimate of orientation is based on sky polarization; and

calculating a position of said target based upon said first location, said first estimate of orientation to said target, said second location, and said second estimate of orientation to said target.

38. A surveying system comprising:

a visual sighting device comprising a distance measuring component; and

a polarization sensor disposed in a known spatial relationship with said visual sighting device.

39. The surveying system of claim 38, further comprising:

an orientation determiner configured to determine an absolute orientation of said visual sighting device based upon at least one sky polarization data set captured by said polarization sensor.

40. The surveying system of claim 39 wherein said orientation determiner is configured to find a best fit between said sky polarization data set and a reference sky polarization data set.

41. The surveying system of claim 40, wherein said reference sky polarization data set comprises a model of sky polarization.

42. The surveying system of claim 40 wherein said reference sky polarization data set comprises a set of sky polarization measurements captured using a second sky polarization sensor having a known absolute orientation.

43. The surveying system of claim 39 further comprising:

a position determiner configured to determine a position of a target based upon said absolute orientation, a distance to said target, and said position at which said surveying system is located.

44. The surveying system of claim 38, further comprising:

a Global Navigation Satellite System (GNSS) receiver configured to determine a position at which said surveying system is located.

45. A compass device comprising:

a polarization sensor configured to capture a sky polarization measurement; and

an orientation determiner configured to determine an absolute orientation of said compass device based upon a comparison of said sky polarization measurement and a sky polarization reference data set.

46. The compass device of claim 45 further comprising:

an input to said orientation determiner configured to receive an indication of the time said sky polarization measurement was taken and to receive an indication of the location at which said sky polarization measurement was taken.

47. The compass device of claim 46 further comprising:

a wireless communications link for receiving said sky polarization reference data set from a polarization reference source.

48. The compass device of claim 46 wherein said sky polarization reference data set comprises a sky polarization model based upon a time when said sky polarization measurement was taken.

49. The compass device of claim 46 wherein said sky polarization reference data set comprises a second sky polarization measurement captured by a second sky polarization sensor having a known absolute orientation.

50. The compass device of claim 46 wherein said sky polarization reference data set comprises a sky polarization model, said compass device further comprising:

a data storage unit for storing said sky polarization model.

51. A vehicle control system comprising:

a polarization sensor configured to capture a sky polarization measurement;

a position determination system for determining a location at which a vehicle is located;

an orientation determiner configured to determine an absolute orientation of said vehicle based upon a comparison of said sky polarization measurement and a sky polarization reference data set; and

a control unit configured to generate a command controlling an operation performed by said vehicle.

52. The vehicle control system of claim 51 further comprising:

an input to said orientation determiner configured to receive an indication of the time said sky polarization measurement was taken and to receive an indication of the location at which said sky polarization measurement was taken.

53. The vehicle control system of claim 52 further comprising:

a wireless communications link for receiving said sky polarization data set from a polarization reference source.

54. The vehicle control system of claim 53 wherein said sky polarization reference data set comprises a sky polarization model based upon a time when said sky polarization measurement was taken.

55. The vehicle control system of claim 53 wherein said sky polarization reference data set comprises a second sky polarization measurement captured by a second sky polarization sensor having a known absolute orientation.

56. The vehicle control system of claim 52 wherein said sky polarization reference data set comprises a sky polarization model, and further comprising:

a data storage unit for storing said sky polarization model.

57. The vehicle control system of claim 51 further comprising:

an input to said control unit configured to receive an indication of said operation.

58. A method for determining the position of a target location comprising:

orienting a visual sighting device and a sky polarization sensor toward a known location wherein said visual sighting device comprises a range measurement system and is disposed in a known spatial relationship with said sky polarization sensor;

generating an estimate of an absolute orientation of said visual sighting device based on sky polarization while determining a distance from said visual sighting device to said known location;

accessing a set of coordinates of said known location;

determining a second spatial relationship between said visual sighting device and said target when said range measurement is captured; and

calculating a location of said target based on said set of coordinates, said distance to said known location, said known spatial relationship, said second spatial relationship, and said absolute orientation of said visual sighting device.

59. The method of claim 58 further comprising:

comparing a sky polarization measurement, captured using said sky polarization sensor, with a sky polarization reference data set to determine said absolute orientation.

60. The method of claim 59 further comprising:

receiving an indication of the time said sky polarization measurement was taken and an indication of the location at which said sky polarization measurement was taken.

61. The method of claim 59 further comprising:

receiving said sky polarization reference data set at said visual sighting device from a polarization reference source.

62. The method of claim 61 further comprising:

comparing a sky polarization measurement, captured using said sky polarization sensor with a sky polarization model based upon a time when said sky polarization measurement was taken.

63. The method of claim 61 further comprising:

comparing a sky polarization measurement, captured using said sky polarization sensor with a second sky polarization measurement captured by a second sky polarization sensor having a known absolute orientation.

64. The method of claim 59 wherein said sky polarization reference data set comprises a sky polarization model, said method further comprising:

storing said sky polarization model at said visual sighting device.