# How to decide whether a person falls down?

• ### Question

• Hi all,

I just wonder how to decide whether a person falls down. Two thoughts come to mind:

1. the difference between y coordinates of the Hipcenter and the foot is within 10cm (for example).

2. Use the w coordinate in FloorClipPlane, when the difference between the y of the Hipcenter and w is larger than some value

Do you have better suggestions? Thanks.

Friday, May 4, 2012 8:35 PM

### All replies

• I would create something like option 1

I would analyze data (hip is very good joint) and if Y position of hip center falls very fast in time of 16 or 32 frames (0,5 - 1 second) I would say that he is falling down. But 10 cm is IMO to small. If the person is falling down you can make a bigger control value

Saturday, May 5, 2012 12:45 PM
• The Kinect’s normal depth vision ranges from around two and a half feet (800mm) to just over 13 feet (4000mm).

However, a recommended usage range is 3 feet to 12 feet as the reliability of the depth values degrade at the edges of the field of view.

Like any camera, the field of view of the depth camera is pyramid shaped. Objects farther away from the camera have a greater lateral range than objects nearer to Kinect. This means that height and width pixel dimensions, such as 640Í480, do not correspond with a physical location in the camera’s field of view. The depth value of each pixel, however, does map to a physical distance in the field of view. Each pixel represented in a depth frame is 16 bits, making the BytesPerPixel property of each frame a value of two. The depth value of each pixel is only 13 of the 16 bits.

Thanks,
MOHAMED A. SAKR | Software Development Lead Engineer | EgyptNetwork
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Monday, May 7, 2012 9:36 AM
• I think your first point is right

1. the difference between y coordinates of the Hipcenter and the foot is within 10cm (for example).

Tuesday, May 8, 2012 4:35 PM