Another question is about the sensor_msgs/pointcloud topic. In the<br>
sensor_msgs/pointcloud document, I don't know how to use the index, distance<br>
and timestamp channel. I want to know how to find the help document.<br>* I also had some trouble finding this information. It is defined in the C++ API for <a href="http://www.ros.org/doc/api/laser_geometry/html/classlaser__geometry_1_1LaserProjection.html">laser_geometry::LaserProjection</a>. I also added a link to this information on the <a href="http://www.ros.org/wiki/laser_assembler">laser_assembler</a> page (which I'm assuming you're using to generate the point clouds).<br>
<br>Hopefully this helps.<br>Vijay<br><br><div class="gmail_quote">On Sun, Jul 4, 2010 at 9:37 AM, Ken Conley <span dir="ltr"><<a href="mailto:kwc@willowgarage.com">kwc@willowgarage.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
For data like this, it's best to use the libraries that come with ROS<br>
to process the data. The data you see is from the tf library, which<br>
has tutorials here:<br>
<br>
<a href="http://www.ros.org/wiki/tf/Tutorials" target="_blank">http://www.ros.org/wiki/tf/Tutorials</a><br>
<br>
I also recommend following the ROS tutorials:<br>
<br>
<a href="http://www.ros.org/wiki/ROS/Tutorials" target="_blank">http://www.ros.org/wiki/ROS/Tutorials</a><br>
<br>
In particular, recording and playing back data:<br>
<br>
<a href="http://www.ros.org/wiki/ROS/Tutorials/Recording%20and%20playing%20back%20data" target="_blank">http://www.ros.org/wiki/ROS/Tutorials/Recording%20and%20playing%20back%20data</a><br>
<br>
You shouldn't have to 'parse' the ROS bag file. ROS bag file data can<br>
be treated identically to the original source of data, so if you write<br>
a node in ROS that subscribes to this data, you simply have to play<br>
the recorded bag data into it to get the same result.<br>
<br>
Hope this helps,<br>
<font color="#888888">Ken<br>
</font><div><div></div><div class="h5"><br>
On Sun, Jul 4, 2010 at 9:31 AM, j2eegirl <<a href="mailto:dp@zju.edu.cn">dp@zju.edu.cn</a>> wrote:<br>
><br>
> My advisor gave me a bag file for a pr2 robot, which includes three kinds of<br>
> topic, namely sensor_msgs/pointcloud, sensor_msgs/pointcloud2 and<br>
> tf/tfmessage.<br>
> I want to get the robot motion information and the obstacle position<br>
> information. From the tf document I can get two kinds of information. One<br>
> kind is of a tree to introduce the relationship of different links. But the<br>
> other kind like this:<br>
> transforms<br>
> [0]<br>
> header<br>
> seq: 0<br>
> stamp: 1274768649205000409<br>
> secs: 1274768649<br>
> nsecs: 205000409<br>
> frame_id: /odom_combined<br>
> child_frame_id: /base_footprint<br>
> transform<br>
> translation<br>
> x: 2.12986805655<br>
> y: -0.140524320055<br>
> z: 0.0<br>
> rotation<br>
> x: 0.00490979815527<br>
> y: 0.00847065476276<br>
> z: 0.721995381834<br>
> w: 0.691828599077<br>
> I want to know how to use the translation and rotation operations.<br>
> Another question is about the sensor_msgs/pointcloud topic. In the<br>
> sensor_msgs/pointcloud document, I don't know how to use the index, distance<br>
> and timestamp channel. I want to know how to find the help document.<br>
> Thank you.<br>
> --<br>
> View this message in context: <a href="http://ros-users.122217.n3.nabble.com/How-to-parse-the-bag-file-tp942523p942523.html" target="_blank">http://ros-users.122217.n3.nabble.com/How-to-parse-the-bag-file-tp942523p942523.html</a><br>
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