[ros-users] About tf and synchronization

[Wim Meeussen]

> So, for the future, I suppose I always have to try to match the time
> of one of the messages, in this case, the point cloud, but, it could
> have been the timestamp of the odometry of amcl_pose?. Is it correct?

You don't have a choice, you need the timestamp of the object you are
transforming. So in your case you are transforming the pc_current
object:

tlistener.transformPointCloud("/map", pc_current, pc_tf);

So you need the timestamp of the pc_current object in the waitForTransform call:

tlistener.waitForTransform("/map", pc_current.header.frame_id,
                              pc_current.header.stamp, ros::Duration(3.0));


The API of tf2 merges the call to waitForTransform and transformObject
into one single call, so it will be impossible to make this kind
mistake.

Wim


-- 
--
Wim Meeussen
Willow Garage Inc.
<http://www.willowgarage.com)