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Understanding the Kinect pointcloud

asked 2011-12-16 09:01:00 -0600

karthik gravatar image

updated 2016-10-24 09:02:37 -0600

ngrennan gravatar image


I saved the pointclouds published by kinect in a pcd file. Width is 640 and height is 480.

I expect kinect to give the x, y, z for every pixel in 640x480.

I believe that the sequence of the pointcloud data starts from the left bottom of the image to the right top of the image, pixel wise left to right.

I understand some of the values are nan as points at that point are not defined as they are not visible or due to some noise.

The z component almost gives the distance of the object from the kinect camera.

I don't understand the values of x y in the point cloud. or they normalized with respect to something, if so how to make it global? Is my understanding wrong and they are still the exact distance in meters? I thought kinect drivers are built for ros so its right to pose this question here.

Thanks, Karthik

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Which driver are you using? openni_camera?
Ivan Dryanovski gravatar image Ivan Dryanovski  ( 2011-12-16 10:30:20 -0600 )edit
karthik gravatar image karthik  ( 2011-12-16 10:37:57 -0600 )edit

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answered 2011-12-16 10:40:21 -0600

z does not give the distance of the point from the camera. (x,y,z) refer to the 3D coordinates of the point in the world in meters (or millimeters, depending), with the camera as the origin (0,0,0).

The depth image, on the other hand, gives the distance from the camera of every pixel in the image.

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Thanks for clarifying !!!
karthik gravatar image karthik  ( 2011-12-16 10:48:50 -0600 )edit

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Asked: 2011-12-16 09:01:00 -0600

Seen: 798 times

Last updated: Dec 16 '11