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transformPointCloud unconnected to tf_broadcaster

asked 2016-06-06 08:39:39 -0500

marilia15 gravatar image

I am using the code tf_broadcaster from the ROS tutorial, but I am using "base_link" and "velodyne" as parent and children in the transformation. I am using "velodyne" because is the frame_id of the pointcloud that my scanner is publishing, please let me know if it is not necessary to have the same name.

And I am using this code for subscribing a pointcloud2 and tf messages and publish a new pointcloud2:

ros::Publisher pub;
tf::Transform transform;
sensor_msgs::PointCloud2 msg2;

void chatterCallback(const sensor_msgs::PointCloud2::ConstPtr& msg) 
  tf::TransformListener tf_listener;
  pcl_ros::transformPointCloud("velodyne", *msg, msg2, tf_listener);    

int main(int argc, char **argv)
  ros::init(argc, argv, "pc2tfpc");
  ros::NodeHandle n ; 
  ros::Subscriber sub = n.subscribe("velodyne_points", 1, chatterCallback); 
  return 0;

I can compile code and execute but the new pointcloud2 has not been transformed with the published tf (I checked it on rviz)

rostopic echo /tf shows the right transformation.

rosrun rqt_graph rqt_graph shows that my code is not subscribed to /tf

If I change the target_frame to "velodyne" ( pcl_ros::transformPointCloud("velodyne", *msg, msg2, tf_listener); ) then I get this error in the execution: "base_link" passed to lookupTransform argument target_frame does not exist.

Anybody has an idea about what is wrong? Thanks in advance.

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answered 2016-06-06 12:16:21 -0500

joq gravatar image

Assuming your tf tree is set up correctly, velodyne_pointcloud provides a transform nodelet that can perform this operation for you.

In your case, set the frame_id parameter to "base_link". (The default is "odom", which is usually what people want.)

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I run the velodyne_node to publish raw data, the tf_broadcaster from the tutorial (parent "base_link", children "velodyne") and the transform_node _frame_id:=/base_link and a calibration file. I get error: Lookup would require extrapolation into the past...from frame [velodyne] to [base_link]

marilia15 gravatar image marilia15  ( 2016-06-08 08:00:05 -0500 )edit

Sounds like something is wrong with your `tf tree or your clock.

joq gravatar image joq  ( 2016-06-08 15:31:44 -0500 )edit

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Asked: 2016-06-06 08:39:39 -0500

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Last updated: Jun 06 '16