AUTOMATED CALIBRATION OF A SURVEYING INSTRUMENT

• US 20110023578A1
• Filed: 02/29/2008
• Published: 02/03/2011
• Est. Priority Date: 02/29/2008
• Status: Active Grant

• Current Assignee: Trimble AB (Trimble Inc.)
• Original Assignee: Trimble AB (Trimble Inc.)
• Inventors: Grässer, Christian
• Granted Patent: US 8,978,440 B2
• Time in Patent Office: Days
• US Class Current: 73/1.75
• CPC Class Codes: G01C 15/00 Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38

Abstract

The present invention provides a method for calibrating a geodetic instrument, an instrument and a computer program product thereof. In the method and geodetic instrument of the present invention, a value of at least one parameter affecting the measurements made by the instrument is detected and compared with a predetermined threshold. On the basis of the comparison between the detected value and the predetermined threshold, the instrument aims at a reference target and a calibration is performed using the reference target. The present invention is advantageous in that the accuracy and reliability of the measurements performed by the instrument are increased. Further, the present invention is advantageous in that the requirements on mechanical stability are reduced.

Claims

1. Method for calibrating a geodetic instrument (200), said method comprising the steps of:

detecting (4010, 5010) a value of at least one parameter affecting the measurements made by said instrument;

comparing (4020, 5020) the detected value of said at least one parameter with a predetermined threshold;

aiming (4030, 5050) said instrument at a reference target (600) on the basis of the comparison between the detected value of said at least one parameter and said predetermined threshold; and

performing (4040, 5060) a calibration using said reference target.

2. The method as defined in claim 1, further comprising the step of recording the detected value of said at least one parameter if said instrument is turned off, wherein the step of comparing the detected value with a predetermined threshold is performed once said instrument is turned on.

3. The method as defined in claim 1 or 2, wherein the step of aiming is performed if the detected value exceeds said predetermined threshold.

4. The method as defined in claim 1 or 2, wherein the step of aiming is performed if the detected value is below said predetermined threshold.

5. The method as defined in any one of the preceding claims, wherein the step of aiming is performed if the detected value exceeds or is below said predetermined threshold by a predefined value.

6. The method as defined in any one of the preceding claims, further comprising the steps of:

generating (5030) an alert on the basis of the comparison between the detected value of said at least one parameter and said predetermined threshold;

receiving (5040), in response to the generated alert, a message including instructions for calibration; and

aiming (5050) said instrument at a reference target if the received message includes instructions to calibrate.

7. The method as defined in claim 6, wherein said alert is generated if the detected value exceeds said predetermined threshold.

8. The method as defined in claim 6, wherein said alert is generated if the detected value is below said predetermined threshold.

9. The method as defined in any one of claims 6-8, wherein said alert is generated if the detected value exceeds or is below said predetermined threshold by a predefined value.

10. The method as defined in any one of the preceding claims, further comprising the step of searching a reference target.

11. The method as defined in any one of claims 1-9, wherein the step of aiming comprises the step of retrieving the position of a reference target used in a previous calibration.

12. The method as defined in any one of the preceding claims, further comprising the step of sending an acknowledgement indicating which instrument settings have been calibrated.

13. The method as defined in claim 12, wherein said acknowledgement comprises the deviation between a calibrated instrument setting and a previous value of said instrument setting.

14. The method as defined in any one of the preceding claims, further comprising the steps of:

comparing an instrument setting obtained during the calibration with tolerance values; and

sending a service message if it is determined that the instrument setting is outside the range defined by the tolerance values.

15. The method as defined in any one of the preceding claims, wherein said at least one parameter is the temperature of said instrument or the ambient temperature.

16. The method as defined in any one of the preceding claims, wherein said at least one parameter is an acceleration, said acceleration representing a mechanical shock or transport stress to which said instrument is subject.

17. The method as defined in any one of the preceding claims, wherein said at least one parameter is a tilt angle, said tilt angle corresponding to the deviation between the instrument vertical axis and a vertical reference plumb axis.

18. The method as defined in any one of the preceding claims, wherein said at least one parameter is a period of time expressed in terms of months, weeks, days, hours, minutes and/or seconds, wherein said period of time corresponds to the periodicity between every calibration of said instrument.

19. The method as defined in any one of the preceding claims, wherein the reference target cooperates with said instrument during said calibration.

20. The method as defined in any one of the preceding claims, wherein the position of said reference target in a coordinated system is fixed.

21. The method as defined in any one of the preceding claims, wherein said reference target is arranged at either one of a Tribrach of said instrument, a base of said instrument and a tripod on which said instrument is mounted.

22. The method as defined in any one of the preceding claims, wherein said calibration includes calibration of a camera (390) of said instrument, wherein said camera includes an image sensor.

23. The method as defined in any one of the preceding claims, wherein said calibration includes calibration of an electronic distance measurement unit (385), EDM unit, of said instrument.

24. The method as defined in claim 23, wherein the calibration of the EDM unit includes the steps of:

scanning (8010) a region comprising said reference target, wherein, for each one of the positions of the scanned region, said method comprises;

transmitting (8020) a radiation beam from said EDM unit towards said position;

receiving (8030) at the EDM unit a radiation beam that is reflected against said position;

recording (8040) the instrument angle corresponding to said position and a signal representative of the received radiation beam associated with said position; and

once all positions of said region have been scanned (8050),

determining (8060, 8070) at least one setting for the EDM unit on the basis of an analysis of the recorded angles and signals.

25. The method as defined in claim 24, wherein the EDM setting corresponds to the angle deviation between the EDM axis and the instrument line of sight.

26. The method as defined in claim 24 or 25, wherein the EDM setting is the operation width of said EDM.

27. The method as defined in any one of claims 24-26, wherein the step of determining at least one EDM setting comprising the steps of:

mapping (8060) the strengths of the recorded signals as a function of the recorded angles; and

extracting (8070) the EDM setting from the mapping.

28. The method as defined in any one of the preceding claims, wherein said calibration includes calibration of a tilt sensor of said instrument.

29. The method as defined in any one of the preceding claims, wherein said calibration includes the step of determining collimation error in the vertical or horizontal dimension of the line of sight of the instrument (135, 335).

30. The method as defined in any one of the preceding claims, wherein said calibration comprises the step of determining the instrument orientation along a horizontal direction

31. The method as defined in claim 30, wherein the instrument orientation along the horizontal direction is determined by comparing an image of said reference target acquired on a camera of said instrument with a stored image acquired at a previous calibration.

70. A computer program product, loadable into an internal memory of a geodetic instrument, comprising software code portions for causing a control unit of said instrument to perform steps in accordance with claims 1-31.

32. A geodetic instrument (200), comprising:

a base (105);

an alidade (115) rotationally mounted on the base for rotation about a first axis (120);

a center unit (125) rotationally mounted on the alidade for rotation about a second axis (130);

a processing unit (150); and

at least one detector (170) for detecting the value of at least one parameter affecting the measurements made by said instrument;

wherein said processing unit is configured to

compare the detected value of said at least one parameter with a predetermined threshold;

control said alidade and said center unit for aiming said instrument at a reference target (600) on the basis of the comparison between the detected value and said predetermined threshold; and

perform calibration of said instrument using said reference target.

33. The geodetic instrument as defined in claim 32, further comprising a memory (180) configured to record the detected value of said at least one parameter if said instrument is turned off, wherein said processing unit is configured to compare the recorded value with a predetermined threshold once said instrument is turned on.

34. The geodetic instrument as defined in claim 32 or 33, wherein said processing unit controls said alidade and said center unit for aiming the instrument at a reference target if the detected value exceeds said predetermined threshold.

35. The geodetic instrument as defined in claim 32 or 33, wherein said processing unit controls said alidade and said center unit for aiming the instrument at a reference target if the detected value is below said predetermined threshold.

36. The geodetic instrument as defined in claim 32-35, wherein said processing unit controls said alidade and said center unit for aiming the instrument at a reference target if the detected value exceeds or is below said predetermined threshold by a predefined value.

37. The geodetic instrument as defined in any one of claims 32-36, wherein said processing unit is further configured to:

generate an alert on the basis of the comparison between the detected value and said predetermined threshold;

receive, in response to the generated alert, a message including instructions for calibration; and

control said alidade and said center unit for aiming said instrument at a reference target if the received message includes instructions to calibrate said instrument.

38. The geodetic instrument as defined in claim 37, wherein said processing unit is configured to generate an alert if the detected value exceeds said predetermined threshold.

39. The geodetic instrument as defined in claim 37, wherein said processing unit is configured to generate an alert if the detected value is below said predetermined threshold.

40. The geodetic instrument as defined in any one of claims 37-39, wherein said processing unit is configured to generate an alert if the detected value exceeds or is below said predetermined threshold by a predefined value.

41. The geodetic instrument as defined in any one of claims 32-40, wherein said processing unit is further configured to search for a reference target.

42. The geodetic instrument as defined in any one of claims 32-40, further comprising a memory configured to record the position of a target reference used in a previous calibration, wherein said processing unit is configured to aim said instrument at said position.

43. The geodetic instrument as defined in any one of claims 32-42, wherein said processing unit is further configured to send an acknowledgement indicating which instrument settings have been calibrated.

44. The geodetic instrument as defined in claim 43, wherein said acknowledgement comprises the deviation between a calibrated instrument setting and a previous value of said instrument setting.

45. The geodetic instrument as defined in any one of claims 32-44, wherein said processing unit is further configured to

compare an instrument setting obtained during the calibration with tolerance values;

and

send a service message if said processing unit determines that the instrument setting is outside the range defined by the tolerance values.

46. The geodetic instrument as defined in any one of claims 32-45, further comprising at least one temperature sensor, wherein said at least one parameter is the temperature of said instrument or the ambient temperature.

47. The geodetic instrument as defined in any one of claims 32-46, further comprising an acceleration sensor, wherein said at least one parameter is an acceleration, said acceleration representing a mechanical shock or transport stress to which said instrument is subject.

48. The geodetic instrument as defined in any one of claims 32-47, further comprising a tilt sensor wherein said at least one parameter is a tilt angle, said tilt angle corresponding to the deviation between the instrument vertical axis and a vertical reference plumb axis.

49. The geodetic instrument as defined in any one of claims 32-48, further comprising a timer, wherein said at least one parameter is a period of time expressed in terms of months, weeks, days, hours, minutes and/or seconds, wherein said period of time corresponds to the periodicity between every calibration of said instrument.

50. The geodetic instrument as defined in any one of claims 32-49, wherein the reference target cooperates with said instrument during the calibration.

51. The geodetic instrument as defined in any one of claims 32-50, wherein the position of said reference target in a coordinated system is fixed.

52. The geodetic instrument as defined in any one of claims 32-51, wherein said reference target is arranged at either one of a Tribrach (175) of said instrument, the base of said instrument and a tripod (110) on which said instrument is mounted.

53. The geodetic instrument as defined in any one of claims 32-52, further comprising a camera including an image sensor, wherein said processing unit is configured to calibrate said camera.

54. The geodetic instrument as defined in any one of claims 32-53, further comprising an electronic measuring device, EDM, wherein said processing unit is configured to calibrate said EDM.

55. The geodetic instrument as defined in claim 54, wherein said processing unit is configured to:

control controllable devices (140, 160) of said instrument for scanning a region comprising said reference target, wherein, for each one of the positions of the scanned region,

said EDM transmits a radiation beam toward said position;

said EDM receives a radiation beam that is reflected against said position;

said processing unit records the instrument angle corresponding to said position and a signal representative of the radiation beam received by the EDM; and

once all positions of said region have been scanned,

said processing unit determines at least one EDM setting on the basis of an analysis of the recorded angles and the recorded signals.

56. The geodetic instrument as defined in claim 55, wherein the EDM setting corresponds to the angle deviation between the EDM axis and the instrument line of sight.

57. The geodetic instrument as defined in claim 55 or 56, wherein the EDM setting is the operation width of said EDM.

58. The geodetic instrument as defined in any one of claims 55-57, wherein said processing unit is further configured to:

map the strengths of the recorded signals as a function of the recorded angles; and

extract the EDM setting from the mapping.

59. The geodetic instrument as defined in any one of claims 32-58, further comprising a tilt sensor, wherein said processing unit is configured to calibrate said tilt sensor.

60. The geodetic instrument as defined in any one of claims 32-59, wherein said processing unit is further configured to determine collimation error in the vertical or horizontal dimension of the line of sight (135, 335).

61. The geodetic instrument as defined in any one of claims 32-59, wherein said processing unit is further configured to determine the instrument orientation along a horizontal direction (130).

62. The geodetic instrument as defined in claim 61, further comprising an image sensor, wherein said processing unit is configured to compare an image of said reference target acquired by said image sensor with a stored image acquired at a previous calibration.

63. Method for informing about the status of a geodetic instrument (200), said method comprising the steps of:

detecting a value of at least one parameter affecting the measurements made by said instrument;

comparing the detected value of said at least one parameter with a predetermined threshold; and

sending an alert on the basis of the comparison between the detected value of said at least one parameter and said predetermined threshold.

64. The method as defined in claim 63, further comprising the step of

performing a calibration if a response to the alert is received.

65. The method as defined in claim 64, further comprising the step of

aiming said instrument at a reference target (600) for performing said calibration.

66. The method as defined in claim 63, wherein said alert comprises a service message advising to perform a service on said geodetic instrument.

67. The method as defined in any one of claims 63-66, wherein the step of sending an alert is performed if the detected value exceeds said predetermined threshold.

68. The method as defined in any one of claims 63-66, wherein the step of sending an alert is performed if the detected value is below said predetermined threshold.

69. The method as defined in any one of the claims 63-66, wherein the step of sending an alert is performed if the detected value exceeds or is below said predetermined threshold by a predefined value.

71. A computer program product, loadable into an internal memory of a geodetic instrument, comprising software code portions for causing a control unit of said instrument to perform steps in accordance with claims 63-69.