LOCALIZATION OF A SURVEYING INSTRUMENT IN RELATION TO A GROUND MARK

• US 20100309311A1
• Filed: 06/26/2008
• Published: 12/09/2010
• Est. Priority Date: 02/12/2008
• Status: Active Grant

• Current Assignee: Trimble AB (Trimble Inc.)
• Original Assignee: Trimble AB (Trimble Inc.)
• Inventors: Svanholm, Set
• Granted Patent: US 8,629,905 B2
• Time in Patent Office: Days
• US Class Current: 348/135
• CPC Class Codes: G01C 1/04 combined with cameras
• CPC Class Codes: G01C 15/00 Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00

Abstract

A method is disclosed for localizing a surveying instrument having a housing including at least one camera in relation to a mark located at a ground level. The method comprises the steps of capturing a first image of the ground below the housing in a first camera position and orientation, wherein the first camera position is eccentric to a vertical rotational axis of the surveying instrument, identifying an object point corresponding to the mark in the first image, measuring first image coordinates of the object point in the first image. The method further comprises the steps of capturing a second image of the ground below the housing in a second camera position and orientation, identifying in the second image, an object point corresponding to the mark, and measuring second image coordinates of the object point in the second image. The height of a rotation center of the surveying instrument above the mark is then determined based on the first camera position and orientation, the first image coordinates, the second camera position and orientation, the second image coordinates, and camera calibration data. Furthermore, a surveying instrument for performing the method is disclosed.

Claims

1. A method for localizing, in relation to a mark located at a ground level, a surveying instrument having a housing including at least one camera, said method comprising:

capturing a first image of the ground below the housing in a first camera position and orientation, said first camera position being eccentric to a vertical rotational axis of the surveying instrument;

identifying an object point corresponding to the mark in the first image;

measuring first image coordinates of the object point in the first image;

capturing a second image of the ground below the housing in a second camera position and orientation;

identifying, in the second image, an object point corresponding to the mark;

measuring second image coordinates of the object point in the second image; and

determining the height of a rotation center of the surveying instrument above the mark based on the first camera position and orientation, the first image coordinates, the second camera position and orientation, the second image coordinates, and camera calibration data.

2. The method of claim 1, further comprising determining the relative two-dimensional coordinates, in a horizontal plane, of the rotation center of the surveying instrument in relation to said mark based on the first camera position and orientation, the first image coordinates and camera calibration data and/or the second camera position and orientation, the second image coordinates and camera calibration data.

3. The method of claim 1, further comprising:

orienting the horizontal pointing direction of said surveying instrument by aiming at a reference point located at a remote position from said surveying instrument, said reference point having a known location in a coordinate system.

4. The method of claim 1, wherein at least one of the mark located at the ground level and the surveying instrument is positioned at a known location in a coordinate system.

5. The method of claim 1, further comprising the step of:

rotating said housing around the rotation center so that the at least one camera is moved from the first camera position and orientation to a second camera position and orientation, said second camera position being eccentric to the vertical rotational axis of the surveying instrument, while retaining the rotation center of the surveying instrument in a fixed position.

6. The method of any claim 1, wherein said instrument comprises at least two cameras of which a first camera is arranged in said first camera position and orientation and a second camera is arranged in said second camera position and orientation, said second camera position being eccentric to the vertical rotational axis of the surveying instrument.

7. The method of claim 1, wherein said instrument comprises at least two cameras of which a first camera is arranged in said first camera position and orientation and a second camera is arranged in said second camera position and orientation, said second camera position being coaxial with the vertical rotational axis of the surveying instrument.

8. The method of claim 1, wherein identifying, in the second image, the object point identified in the first image comprises:

determining an epipolar line in the second image on which the object point is located based on the first camera position and orientation, the second camera position and orientation, the first image coordinates, and camera calibration data; and

identifying, along the epipolar line in the second image, the object point identified in the first image.

9. The method of claim 8, wherein identifying, in the second image, the object point identified in the first image further comprises:

selecting a minimum distance and a maximum distance from the first camera position along an imaging ray of the mark in the first image, between which minimum distance and maximum distance the mark is located;

determining, based on the maximum distance and the minimum distance, a section of the epipolar line in the second image on which the object point is located; and

identifying, along the section of the epipolar line in the second image, the object point identified in the first image.

10. The method of claim 8, further comprising:

determining whether the epipolar line is completely inside the second image.

11. The method of claim 10, further comprising:

rotating, if the epipolar line is not completely inside the second image, the surveying instrument around the rotation center based on epipolar line data, the second camera position and orientation and second camera calibration data to a revised second camera position and orientation in order to obtain a new epipolar line within a revised second image;

capturing the revised second image using the camera in the revised second position and orientation; and

identifying, along the new epipolar line in the revised second image, the object point identified in the first image.

12. The method of claim 1, wherein the object point is identified in the images by means of operator selection or automatic image analysis.

13. A computer program product comprising computer program code portions adapted to perform the method of claim 1 when loaded and executed in a computer.

14. A surveying instrument, comprising:

at least one camera adapted to capture a first image of the ground below the housing in a first camera position and orientation and a second image of the ground below the housing in a second camera position and orientation, said first camera position being eccentric to the vertical rotational axis of the surveying instrument;

an identifying unit adapted to identify an object point corresponding to a mark located at a ground level under said instrument in the captured images;

a measuring unit adapted to measure first and second image coordinates of the object point in the first and second images; and

a processor adapted to determine the height of a rotation center of the surveying instrument above the mark based on the first position and orientation, the first image coordinates, the second position and orientation, the second image coordinates, and camera calibration data.

15. The surveying instrument of claim 14, wherein said processor is further adapted to determine the relative two-dimensional coordinates, in a horizontal plane, of the rotation center of the surveying instrument in relation to said mark based on the first camera position and orientation, the first image coordinates and camera calibration data, and/or the second camera position and orientation, the second image coordinates and camera calibration data.

16. The surveying instrument of claim 14, wherein said processor is further adapted to orientate the horizontal pointing direction of said instrument in relation to a reference point located at a remote position from said surveying instrument, said reference point having a known location in a coordinate system.

17. The surveying instrument of claim 14, wherein at least one of the mark and the surveying instrument is positioned at a known location in a coordinate system.

18. The surveying instrument of claim 14, further comprising:

a rotating unit adapted to rotate, while retaining the rotation center of the surveying instrument in a fixed position, the surveying instrument around the rotation center of the surveying instrument so that the camera is moved from the first camera position and orientation to the second camera position and orientation, said second camera position being eccentric to the vertical rotational axis of the instrument.

19. The surveying instrument of claim 14, comprising at least two cameras of which a first camera is arranged in said first camera position and orientation and a second camera is arranged in said second camera position and orientation, said second camera position being eccentric to the vertical rotational axis of the instrument.

20. The instrument of claim 14, wherein the identifying unit is implemented as a cursor movable across the displayed images, using image processing software or using a touch display where the object point can be identified by clicking or tapping on the display.