How to tell what units a point cloud is in?

Question

I am using a dataset of point cloud files created from Kinect images. Is there a way to know what units the axis are in, i.e. for a point (0.003, 0.004, 0.04) is this meters, centimeters etc.?

I am trying to estimate surface normals from local patches using the setRadiusSearch method in pcl but this allows us to specify a radius in meters, so I need to know the units of the point cloud.

Answer 1

The axis in your viewer is whatever units you want it to be. You have to know or infer the actual units from your source. For example, the MS driver returns values in mm. Since you are dealing with a Kinect point cloud, irrespective of the drivers you can easily figure out what your values represent: The Kinect has a range of 0.4 to 8 m. That means that -for example- if the values are like (500.0, 600.0, 3000.0) this means they are in mm, if they are (0.5, 0.6, 2.0) then they are in m, and so on.