DETERMINING CAMERA HEIGHT USING DISTRIBUTIONS OF OBJECT HEIGHTS AND OBJECT IMAGE HEIGHTS

• US 20140293043A1
• Filed: 03/28/2013
• Published: 10/02/2014
• Est. Priority Date: 03/28/2013
• Status: Active Grant

• Current Assignee: Kyndryl Incorporated
• Original Assignee: International Business Machines Corporation
• Inventors: Datta, Ankur, Feris, Rogerio S., Pankanti, Sharathchandra U., Zhai, Yun
• Granted Patent: US 9,322,647 B2
• Time in Patent Office: Days
• US Class Current: 348/135
• CPC Class Codes: G01C 5/00 Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels G01C3/20, G01C3/30 take precedence
• CPC Class Codes: G06F 18/22 Matching criteria, e.g. proximity measures
• CPC Class Codes: G06T 2207/30196 Human being; Person
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: G06T 7/55 from multiple images
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes
• CPC Class Codes: H04N 7/18 Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast

Abstract

A camera at a fixed vertical height positioned above a reference plane, with an axis of a camera lens at an acute angle with respect to a perpendicular of the reference plane. One or more processors receive images of different people. The vertical measurement values of the images of different people are determined. The one or more processors determine a first statistical measure associated with a statistical distribution of the vertical measurement values. The known heights of people from a known statistical distribution of heights of people are transformed to normalized measurements, based in part on a focal length of the camera lens, the angle of the camera, and a division operator in an objective function of differences between the normalized measurements and the vertical measurement values. The fixed vertical height of the camera is determined, based at least on minimizing the objective function.

Claims

1. A method for determining a height of a camera, the camera at a fixed vertical height positioned above a reference plane, an axis of a lens of the camera at an acute angle with respect to a perpendicular of the reference plane, the method comprising the steps of:

receiving from the camera, a multiplicity of images of a multiplicity of different people;

determining, by one or more processors, vertical measurement values of the multiplicity of images of the multiplicity of different people;

determining, by one or more processors, a first statistical measure associated with a statistical distribution of the vertical measurement values;

transforming, based on one or more processors, known heights of people from a known statistical distribution of heights of people, with respect to the first statistical measure, to normalized measurements of known heights of people, based in part on a focal length of the lens of the camera, the acute angle of the camera, and a division operator present in an objective function of differences between the normalized measurements of known heights of people and the vertical measurement values; and

determining, by one or more processors, the fixed vertical height of the camera, based at least on minimizing the objective function of the differences between the normalized measurements of known heights of people and the vertical measurement values.

2. The method of claim 1, wherein transforming, based on one or more processors, known heights of people from a known statistical distribution of heights of people, comprises:

generating, by one or more processors, a multiple row transformation matrix that includes the focal length of the lens of the camera, the acute angle of the camera, and a current estimated camera height;

generating, by one or more processors, normalized measurements of known heights of people from a product of the multiple row transformation matrix and respective known heights of people, including a division operator from a row of the multiple row transformation matrix; and

generating by one or more processors, a value of an error term from a summation of differences between the normalized measurements of known heights of people and the vertical measurement values.

3. The method of claim 2, further comprising:

determining, by one or more processors, a new estimated camera height by adjusting the current estimated camera height, based at least on the error term;

determining, by one or more processors, if a threshold value exceeds the value of the error term; and

in response to determining the threshold value to exceed the value of the error term, one or more processors determining the new estimated camera height to be the fixed vertical height of the camera.

4. The method of claim 1, wherein a multiplicity of different people comprises a multiplicity of different people of a known gender.

5. The method of claim 1, wherein a multiplicity of the different people comprises a multiplicity of different people of known age groups.

6. The method of claim 1, wherein the vertical measurement values of the images of the multiplicity of different people and the normalized measurements of known heights of people from a known statistical distribution of heights of people, are non-parametric.

7. The method of claim 1, wherein the known height of people from a known statistical distribution of height of people is a statistical average of the known statistical distribution of height of people.

8. A computer program product for determining a height of a camera, the camera at a fixed vertical height positioned above a reference plane, an axis of a lens of the camera at an acute angle with respect to a perpendicular of the reference plane, comprising:

one or more computer-readable storage devices and program instructions stored on the one or more computer-readable storage media, the program instructions comprising;

program instructions to receive from the camera, a multiplicity of images of a multiplicity of different people;

program instructions to determine, by one or more processors, vertical measurement values of the multiplicity of images from the camera of the multiplicity of different people;

program instructions to determine, by one or more processors, a first statistical measure associated with a statistical distribution of the vertical measurement values;

program instructions to transform, by one or more processors, known heights of people from a known statistical distribution of heights of people, with respect to the first statistical measure, to normalized measurements of known heights of people, based in part on a focal length of the lens of the camera, the acute angle of the camera, and a division operator present in an objective function of differences between the normalized measurements of known heights of people and the vertical measurement values; and

program instructions to determine, by one or more processors, the fixed vertical height of the camera, based at least on minimizing the objective function of the differences between the normalized measurements of known heights of people and the vertical measurement values.

9. The computer program product of claim 8, wherein transforming known heights of people from a known statistical distribution of heights people, by one or more processors, further comprises:

program instructions to generate, by one or more processors, a multiple row transformation matrix that includes the focal length of the lens of the camera, the acute angle of the camera, and a current estimated camera height;

program instructions to generate, by one or more processors, normalized measurements of known heights of people from a product of the multiple row transformation matrix and respective known heights of people, including a division operator from a row of the multiple row transformation matrix; and

program instructions to generate, by one or more processors, a value of an error term from a summation of the differences between the normalized measurements of known heights of people and the vertical measurement values.

10. The computer program product of claim 9, further comprising:

program instructions to determine, by one or more processors, a new estimated camera height by adjusting the current estimated camera height, based at least on the value of the error term;

program instructions to determine, by one or more processors, if a threshold value exceeds the value of the error term; and

in response to determining, by one or more processors, the threshold value to exceed the value of the error term, program instructions to determine the new estimated camera height to be the fixed vertical height of the camera.

11. The computer program product of claim 8, wherein a multiplicity of different people comprises a multiplicity of different people of a known gender.

12. The computer program product of claim 8, wherein a multiplicity of the different people comprises a multiplicity of different people of known age groups.

13. The computer program product of claim 8, wherein the vertical measurement values of the images of the multiplicity of different people and the normalized measurements of known heights of people from a known statistical distribution of heights of people, are non-parametric.

14. The method of claim 8, wherein the known height of people from a known statistical distribution of height of people is a statistical average of the known statistical distribution of height of people.

15. A computer system for determining a height of a camera, the camera at a fixed vertical height positioned above a reference plane, an axis of a lens of the camera at an acute angle with respect to a perpendicular of the reference plane, the computer system comprising:

one or more computer processors;

one or more computer-readable memories;

one or more computer-readable storage devices;

program instructions stored on the one or more computer-readable storage devices for execution by the one or more processors via the one or more computer-readable memories, the program instructions comprising;

program instructions to receive from the camera, a multiplicity of images of a multiplicity of different people;

program instructions to determine, by one or more processors, vertical measurement values of the multiplicity of images from the camera of the multiplicity of different people;

program instructions to determine, by one or more processors, a first statistical measure associated with a statistical distribution of the vertical measurement values;

program instructions to transform, by on one or more processors, known heights of people from a known statistical distribution of heights of people, with respect to the first statistical measure, to normalized measurements of known heights of people, based in part on a focal length of the lens of the camera, the acute angle of the camera, and a division operator present in an objective function of differences between the normalized measurements of known heights of people and the vertical measurement values; and

program instructions to determine, by one or more processors, the fixed vertical height of the camera, based at least on minimizing the objective function of the differences between the normalized measurements of known heights of people and the vertical measurement values.

16. The computer system of claim 15, wherein transforming known heights of people from a known statistical distribution of heights people by one or more processors, further comprises:

program instructions to generate, by one or more processors, a multiple row transformation matrix that includes the focal length of the lens of the camera, the acute angle of the camera, and a current estimated camera height;

program instructions to generate, by one or more processors, normalized measurements of the known height of people by a product of the multiple row transformation matrix and respective known heights of people, including a division operator from a row of the multiple row transformation matrix; and

program instructions to generate, by one or more processors, a value of an error term from a summation of differences between the normalized measurements of known heights of people and the vertical measurement values.

17. The computer system of claim 16, further comprising:

program instructions to determine, by one or more processors, a new estimated camera height by adjusting the current estimated camera height, based at least on the error term;

program instructions to determine, by one or more processors, if a threshold value exceeds the value of the error term; and

in response to determining, by one or more processors, the threshold value to exceed the value of the error term, program instructions to determine the new estimated camera height to be the fixed vertical height of the camera.

18. The computer system of claim 15, wherein a multiplicity of different people comprises a multiplicity of different people of a known gender.

19. The computer system of claim 15, wherein a multiplicity of the different people comprises a multiplicity of different people of known age groups.

20. The computer system of claim 15, wherein the known height of people from a known statistical distribution of height of people is a statistical average of the known statistical distribution of height of people.