About number of LiDAR channels

[qymao]

Thank you for your team's wonderful work! I am wondering the many channels are the 5 LiDARs in Waymo open dataset? Could you please provide some details? Thanks a lot!

[peisun1115]

Not sure what do you mean by 'channels'. We have detailed description of the LiDAR in the paper.

[Kin-Zhang]

I think the channel definition may misleading sometimes. I think here are two meaning:

1. feature channel in each point: like (x,y,z) is the basic three channels for one point cloud.
2. density channel in LiDAR type: like KITTI uses 64-channel LiDAR, Nuscene use 32-channel LiDAR etc.

The first feature channel may easily found in waymo paper and also README: they have 6 feature channels that are <range, intensity, elongation, x, y, and z>.

TOP_RANGE_IMAGE_FIRST_RETURN is <class 'numpy.ndarray'> (64, 2650, 6), HxWx6 The six channels are range, intensity, elongation, x, y, and z. The x, y, and z values are in vehicle frame.

The second density channel: Recently I have also been curious about how density channel Waymo has, but I didn't find any official document that indicates what type of LiDAR they use.
But from the last answer, we can give a guess since the range image is (64,2650), the density channel may be the same as KITTI which is 64-channel LiDAR. (But through below image I would say maybe between 32-64 channel LiDAR. 😄

And a quick preview on three different dataset one frame point cloud: