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Understanding velodyne transform_node vs cloud_node to transform point clouds

asked 2016-05-31 11:53:54 -0500

Venkat Ganesh gravatar image

updated 2016-05-31 13:20:33 -0500

Hello!

I was looking into the source code for the velodyne package and I've a couple of questions about cloud_node and transform_node which I'm hoping to learn more about.

Consider the following cases:

Case 1: I use the cloud_node to get point clouds in the 'velodyne' frame. Given the velodyne->odom transform exists, I can use tf to transform the point clouds to the odom frame.

Case 2: I use the transform_node, VelodynePackets are unpacked into point clouds and transform for
velodyne->odom is applied within the node (from line 111 in transform.cc)

pcl_ros::transformPointCloud(inPc_.header.frame_id,
                                     ros::Time(0), inPc_,
                                     config_.frame_id,
                                     tfPc_, listener_);

Here's my question: Is there any advantage to transforming point clouds from individual VelodynePackets (in Case 2), as opposed to the full point cloud (Case 1)? When would I use one over the other?

Thanks!

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answered 2016-06-01 21:12:35 -0500

joq gravatar image

The main use of transform_node is when the device is moving fast enough for the transforms to change significantly during the 0.1 second required for a full revolution (assuming 600 RPM). This is especially important if the heading changes.

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Asked: 2016-05-31 11:53:54 -0500

Seen: 327 times

Last updated: Jun 01 '16