DETERMINING COORDINATES OF A TARGET IN RELATION TO A SURVEY INSTRUMENT HAVING AT LEAST TWO CAMERAS

• US 20110043620A1
• Filed: 02/29/2008
• Published: 02/24/2011
• Est. Priority Date: 02/29/2008
• Status: Active Grant

• Current Assignee: Trimble AB (Trimble Inc.)
• Original Assignee: Trimble AB (Trimble Inc.)
• Inventors: Svanholm, Set, Vogel, Michael, Grässer, Christian
• Granted Patent: US 9,189,858 B2
• Time in Patent Office: Days
• US Class Current: 348/135
• CPC Class Codes: G01C 1/04 combined with cameras
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G06T 7/55 from multiple images

Abstract

A method is disclosed for determining coordinates of a target in relation to a surveying instrument wherein a first image is captured using a first camera in a first camera position and orientation, a target is selected by identifying at least one object point in the first image, and first image coordinates of the object point in the first image are measured. In at least one embodiment, a second image is captured using a second camera in a second camera position and orientation, the object point identified in the first image is identified in the second image, and second image coordinates of the object point in the second image are measured. Target coordinates of the target in relation to the rotation center of the surveying instrument are 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 first and second camera calibration data. Furthermore, a surveying instrument for performing the method is disclosed.

Claims

1. A method for determining coordinates of a target in relation to a surveying instrument comprising a first camera in a first camera position and orientation, and a second camera in a second camera position and orientation, the method comprising:

capturing a first image using the first camera;

selecting a target by identifying at least one object point in the first image;

measuring first image coordinates of the at least one object point in the first image;

capturing a second image using the second camera;

identifying, in the second image, the at least one object point identified in the first image, further comprising;

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

determining a section of an epipolar line in the second image on which the at least one object point is located based on the maximum distance, the minimum distance, the first camera position and orientation, the second camera position and orientation, the first image coordinates, and first and second camera calibration data; and

identifying, along the section of the epipolar line in the second image, the at least one object point identified in the first image;

measuring second image coordinates of the at least one object point in second image; and

determining target coordinates of the target in relation to the rotation center of the surveying instrument based on the first camera position and orientation, the first image coordinates, the second camera position and orientation, the second image coordinates, and first and second camera calibration data.

2. The method of claim 1, further comprising:

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

3. The method of claim 2, 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 position the 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 section of the epipolar line in the revised second image, the at least one object point identified in the first image.

4. The method of claim 1, wherein the minimum distance is selected as the minimum distance of the surveying instrument.

5. The method of claim 1, wherein the at least one object point is identified in the first image by means of operator selection.

6. The method of claim 1, wherein the at least one object point is identified in the first image by means of automatic image analysis.

7. The method of claim 1, wherein the at least one object point identified in the first image is identified in the second image by means of automatic image analysis.

8. The method of claim 1, wherein the at least one object point identified in the first image is identified in the second image by means of user selection.

9. The method of claim 1, wherein the first and second image are captured while the target is illuminated by way of a light source, and two further images are captured with the light source turned off, where one of the two images of the first camera is subtracted from the other one of the two images of the first camera in order to produce a first difference image and one of the two images of the second camera is subtracted from the other one of the two images of the second camera in order to produce a second difference image, and wherein said target is selected by identifying at least one object point in the first difference image;

first image coordinates of the at least one object point are measured in the first difference image;

the at least one object point identified in the first difference image is identified in the second difference image;

second image coordinates of the at least one object point are measured in the second difference image; and

target coordinates of the target in relation to the rotation center of the surveying instrument are determined based on the first camera position and orientation, the first difference image coordinates, the second camera position and orientation, the second difference image coordinates, and first and second camera calibration data.

10. The method of claim 9, said light source emitting the target by way of a spot.

11. The method of claim 9, said light source emitting the target by way of a projected pattern.

12. The method of claim 1, wherein a number of images are captured with the two cameras in order to attain a scanning function, where an image of the first camera is processed with a corresponding image of the second camera in order to determine target coordinates for each pair of captured first and second images.

13. The method of claim 1, further comprising:

determining a direction from the rotation center of the surveying instrument towards the target based on the determined target coordinates.

14. The method of claim 13, further comprising:

rotating the surveying instrument so that a line of sight of the surveying instrument is directed in the direction towards the target.

15. The method of claim 14, further comprising:

measuring a distance to the target using distance measuring capabilities within the surveying instrument

16. The method of claim 1, further comprising:

determining a distance from the rotation center of the surveying instrument to the target based on the determined target coordinates.

17. The method of claim 1, wherein the first image and the second image are captured simultaneously.

18. A method for determining coordinates of a target in relation to a surveying instrument, in which the method of claim 1, or electronic distance measurement, can be selectively applied for determining the target coordinates.

19. A method for determining coordinates of a target in relation to a surveying instrument, said method using the method of claim 1 at close range, and electronic distance measurement at far range for determining the target coordinates.

20. The method of claim 19, wherein close range is defined as up to 25 meters from the target.

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

22. The computer program product of claim 21, stored on a computer readable medium.

23. A surveying instrument, comprising:

a first camera operable to capture images from a first position and orientation;

a second camera operable to capture images from a first position and orientation;

means for displaying images captured by the first camera and the second camera;

means for identifying an object point corresponding to a selected target in the displayed images, wherein said means for identifying is adapted to;

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

determine a section of an epipolar line in the second image on which the at least one object point is located based on the maximum distance, based on the maximum distance, the minimum distance, the first camera position and orientation, the second camera position and orientation, the first image coordinates, and first and second camera calibration data; and

identify, along the section of the epipolar line in the second image, the at least one object point identified in the first image;

measuring second image coordinates of the at least one object point in second image; and

means for measuring image coordinates of the object point in the displayed images; and

means for determining target coordinates of the target in relation to the rotation center of the surveying instrument, 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.

24. The instrument of claim 23, wherein the means for identifying an object point is implemented as a cursor movable across the displayed images.

25. The instrument of claim 23, wherein the means for identifying an object point is implemented using a touch display, where the object point can be identified by clicking or tapping on the display.

26. The instrument of claim 23, wherein the means for identifying an object point is further implemented using image processing software.

27. The instrument of claim 23, further comprising:

means for emitting light pulses towards the target in order to perform electronic distance measurements.

28. The instrument of claim 23, further comprising:

means for illuminating the selected target,

29. The instrument of claim 28, wherein the means for illuminating the selected target is arranged coaxially with the means for emitting light pulses towards the target.

30-32. -32. (canceled)