Methods, apparatus and articles of manufacture to monitor environments

1. A method, comprising:

analyzing, with a processor, a first depth value corresponding to a coordinate of an object of an image captured by a depth sensor, the first depth value having been captured with the depth sensor positioned at a first angle relative to a reference axis;

initiating, with the processor, the depth sensor to move to a second angle relative to the reference axis, the second angle being different than the first angle;

triggering, with the processor, capture of a second depth value at the coordinate with the depth sensor positioned at the second angle; and

calculating, with the processor, a depth gradient for the coordinate based on the first depth value, the second depth value, and a difference between the first angle and the second angle.

2. A method as defined in claim 1 , wherein the moving of the depth sensor to the second angle is based on a comparison of the first depth value and a threshold.

3. A method as defined in claim 2 , wherein a value of the threshold depends on whether the object, a movement, or a gesture is being analyzed.

4. A method as defined in claim 1 , wherein the moving of the depth sensor to the second angle is in response to detecting movement at the coordinate.

5. A method as defined in claim 1 , wherein the moving of the depth sensor includes actuating a tilt motor coupled to a housing of the depth sensor.

6. A method as defined in claim 1 , further including triggering capture of a third depth value at the coordinate with the depth sensor positioned at a third angle relative to the reference axis, the third angle being different than the first and second angles.

7. A method as defined in claim 6 , wherein the calculating of the depth gradient for the coordinate includes consideration of the third depth value.

8. A method as defined in claim 1 , wherein the reference axis is a horizontal axis extending away from the depth sensor into the environment.

9. A tangible machine readable storage medium comprising instructions that, when executed, cause a machine to at least:

identify a first depth value corresponding to a coordinate of an object in a first image captured by a depth sensor, the first image having been captured with the depth sensor positioned at a first angle relative to a reference axis;

determine whether a condition associated with a recognition analysis is present at the coordinate; and

in response to the condition being present at the coordinate:

trigger capture of a second image at the coordinate with the depth sensor positioned at a second angle relative to the reference axis, the second angle being different than the first angle;

identify a second depth value corresponding to the coordinate of the object in the second image; and

calculate an accumulated value for the coordinate based on a difference between the first angle and the second angle and on a difference between the first and second depth values.

10. A storage medium as defined in claim 9 , wherein the condition includes an indication that a person is detected at the coordinate at a distance from the depth sensor greater than a threshold distance associated with a person detector.

11. A storage medium as defined in claim 9 , wherein the condition includes an indication that movement is detected at the coordinate at a distance from the depth sensor greater than a threshold distance associated with a movement detector.

12. A storage medium as defined in claim 9 , wherein the condition includes an indication that a gesture is detected at the coordinate at a distance from the depth sensor greater than a threshold distance associated with a gesture detector.

13. A storage medium as defined in claim 9 , wherein the instructions, when executed, cause the machine to identify a third depth value at the coordinate in a third image captured with the depth sensor positioned at a third angle relative to the reference axis, the third angle being different than the first and second angles.

14. A storage medium as defined in claim 13 , wherein the instructions, when executed, cause the machine to calculate the accumulated value based on the first, second and third depth values.

15. An audience measurement device, comprising:

a recognizer to identify an object as likely being a person by analyzing data representative of an environment; and

a depth analyzer to, when a first depth value associated with a coordinate of the object captured by a depth sensor with the depth sensor oriented along a first axis is greater than a threshold distance from the depth sensor:

cause the depth sensor to capture a second depth value at the coordinate with the depth sensor positioned at a first tilt relative to the first axis; and

calculate an accumulated value for the coordinate based on (1) a comparison of the first depth value and the second depth value and (2) an angle of the first tilt;

at least one of the recognizer or the depth analyzer being implemented via a logic circuit.

16. An audience measurement device as defined in claim 15 , wherein the angle is different than a baseline angle.

17. An audience measurement device as defined in claim 15 , wherein the recognizer is to use the accumulated value to confirm that the object is a person.

18. An audience measurement device as defined in claim 15 , wherein the depth analyzer is to actuate a tilt motor to move the depth sensor to the first tilt from the first axis.

19. An audience measurement device as defined in claim 15 , wherein the angle is a particular number of degrees away from the first axis, the first axis extending away from the depth sensor.

20. An audience measurement device as defined in claim 15 , wherein the depth sensor is to utilize a projected dot array, and a first dot of the dot array corresponds to the coordinate.

21. An apparatus, comprising:

a depth sensor to collect images of an environment, the depth sensor having a housing;

a tilt motor to tilt the housing of the depth sensor relative to a reference axis; and

a processor to:

determine a first depth value associated with a coordinate of a first image collected with the housing at a first angle relative to the reference axis;

instruct the tilt motor to move the housing to a second angle relative to the reference axis, the second angle being different from the first angle;

determine a second depth value associated with the coordinate in a second image collected by the depth sensor with the housing at the second angle; and

calculate a depth gradient for the coordinate based on the first depth value, the second depth value, and a difference between the first angle and the second angle.

22. A method, comprising:

analyzing, with a processor, a first depth value corresponding to a coordinate of an object of an image captured by a depth sensor, the first depth value having been captured with the depth sensor positioned at a first angle relative to a reference axis;

moving, with the processor, the depth sensor to a second angle relative to the reference axis, the second angle being different than the first angle;

triggering, with the processor, capture of a second depth value at the coordinate with the depth sensor positioned at the second angle; and

calculating, with the processor, a depth gradient for the coordinate based on the first depth value, the second depth value, and the second angle;

wherein the calculating of the depth gradient for the coordinate based on the first depth value, the second depth value, and the second angle includes:

calculating a first difference between the first depth and the second depth;

calculating a second difference between the first angle and the second angle; and

calculating a ratio of the first difference and the second difference.