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Publish Laser Scan

asked 2012-06-04 03:14:10 -0500

allenh1 gravatar image

updated 2012-06-05 09:26:16 -0500

Hello all,

I have a node that generates a point cloud. How do I take the data and output a laser scan? The pointcloud_to_laserscan node isn't working for me... I guess I need to convert the data to polar and publish it. The math I can do, but could you help me with publishing the laser scan?

Thanks, -Hunter A.

Here is the launch file. The topic "scan" is not publishing when I use this launch file and start my node [If you guys could help start the node from this launch file, that would be cool too].

<launch>
   <!-- throttling -->
  <node pkg="nodelet" type="nodelet" name="pointcloud_throttle" args="load pointcloud_to_laserscan/CloudThrottle openni_manager" respawn="true">
    <param name="max_rate" value="20.0"/>
    <remap from="cloud_in" to="/laser_ReadOut/cloud_pcl"/>
    <remap from="cloud_out" to="cloud_throttled"/>
  </node>

  <!-- Fake Laser -->
  <node pkg="nodelet" type="nodelet" name="laserOut" args="load pointcloud_to_laserscan/CloudToScan openni_manager" respawn="true">
    <param name="output_frame_id" value="laser"/>
    <!-- heights are in the (optical?) frame of the kinect -->
    <param name="min_height" value="-0.15"/>
    <param name="max_height" value="0.15"/>
    <remap from="cloud" to="/cloud_throttled"/>
  </node>

  <!-- Fake Laser (narrow one, for localization -->
  <node pkg="nodelet" type="nodelet" name="kinect_laser_narrow" args="load pointcloud_to_laserscan/CloudToScan openni_manager" respawn="true">
    <param name="output_frame_id" value="/camera_depth_frame"/>
    <!-- heights are in the (optical?) frame of the kinect -->
    <param name="min_height" value="-0.025"/>
    <param name="max_height" value="0.025"/>
    <remap from="cloud" to="/cloud_throttled"/>
    <remap from="scan" to="/narrow_scan"/>
  </node>
</launch>

Here's an rxgraph: RXgraph Output

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Comments

I see now (thank you @lindzey) that the topics are not connected. How do I connect them properly?

allenh1 gravatar imageallenh1 ( 2012-06-04 06:15:17 -0500 )edit

I have edited my answer below.

karthik gravatar imagekarthik ( 2012-06-04 06:52:34 -0500 )edit

I have edited my answer below.

karthik gravatar imagekarthik ( 2012-06-04 06:52:37 -0500 )edit

I'm not sure what you want me to do with that answer.... Would you mind explaining it and how to apply it?

allenh1 gravatar imageallenh1 ( 2012-06-05 09:15:24 -0500 )edit

Maybe it's not actually a node I'm creating... It's a binary that I execute with "rosrun". I don't have a launch file for it. Is this why I am having trouble with pointcloud_to_laserscan?

allenh1 gravatar imageallenh1 ( 2012-06-05 09:17:44 -0500 )edit

Now (as usual), new problems are found. It is working, but only one beam is being projected...

allenh1 gravatar imageallenh1 ( 2012-06-05 09:40:22 -0500 )edit

1 Answer

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answered 2012-06-04 03:55:09 -0500

karthik gravatar image

updated 2012-06-04 06:52:07 -0500

Hi, I have seen the kinect.launch file under turtlebot_bringup package doing the conversion of the pointcloud to laser scan and publishing it. Here is the part of the launch file which throttles the kinect cloud and converts it into Fake laser scan. May be this will give you some idea to go about the same. If you are using the kinect to get the pointcloud then may be you can directly use it. But this is just going to give the 2D laser scan of the z=0 plane which the kinect is viewing the scene.

  <!-- throttling -->
  <node pkg="nodelet" type="nodelet" name="pointcloud_throttle" args="load pointcloud_to_laserscan/CloudThrottle openni_manager" respawn="true">
    <param name="max_rate" value="20.0"/>
    <remap from="cloud_in" to="/camera/depth/points"/>
    <remap from="cloud_out" to="cloud_throttled"/>
  </node>

  <!-- Fake Laser -->
  <node pkg="nodelet" type="nodelet" name="kinect_laser" args="load pointcloud_to_laserscan/CloudToScan openni_manager" respawn="true">
    <param name="output_frame_id" value="/camera_depth_frame"/>
    <!-- heights are in the (optical?) frame of the kinect -->
    <param name="min_height" value="-0.15"/>
    <param name="max_height" value="0.15"/>
    <remap from="cloud" to="/cloud_throttled"/>
  </node>

  <!-- Fake Laser (narrow one, for localization -->
  <node pkg="nodelet" type="nodelet" name="kinect_laser_narrow" args="load pointcloud_to_laserscan/CloudToScan openni_manager" respawn="true">
    <param name="output_frame_id" value="/camera_depth_frame"/>
    <!-- heights are in the (optical?) frame of the kinect -->
    <param name="min_height" value="-0.025"/>
    <param name="max_height" value="0.025"/>
    <remap from="cloud" to="/cloud_throttled"/>
    <remap from="scan" to="/narrow_scan"/>
  </node>

You could probably check the entire launch file under turtlebot_bringup package. Hope it helps!!!

Karthik


When i was using i figured out a problem with the nodelet not being run by the launch file automatically. So i had to run it in order to correct the nodes. Please check my answer here which should solve your issue. Let me know if not.

Hope it helps!!!

Karthik

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Comments

Ok. I am having issues still. The name of the point cloud I am publishing is "\cloud_pcl". I can visualize it in RVIZ, so it is valid. That being said, I need to get laser data from it. What happens when you load the argument: args="load pointcloud_to_laserscan/CloudThrottle openni_manager" ?

allenh1 gravatar imageallenh1 ( 2012-06-04 04:04:48 -0500 )edit

If you've tried @karthik's launch file and it still doesn't work for you, I suspect that you're having issues with topic naming. My first guess would be that you need to change the line starting "<remap from="cloud_in" ...."

lindzey gravatar imagelindzey ( 2012-06-04 05:50:54 -0500 )edit
1

And, for debugging problems like that in general, look at "rostopic list" and "rxgraph" to make sure that nodes you expect to be connected actually are.

lindzey gravatar imagelindzey ( 2012-06-04 05:52:41 -0500 )edit

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Asked: 2012-06-04 03:14:10 -0500

Seen: 1,830 times

Last updated: Jun 05 '12