Re: [ros-users] TF_OLD data error while using scan_assembler…

Ah I see, that makes sense. Although this still doesn't explain why
the laser_assembler is returning clouds of size 0 to the
periodic_snapshotter even when the system first starts up. If it
helps with debugging I'm using the laser.bag file from the tutorial
and the following launch file (also nabbed from the tutorial):

<launch>
  <node type="laser_scan_assembler" pkg="laser_assembler" name="my_assembler">
    <remap from="scan" to="tilt_scan"/>
    <param name="max_scans" type="int" value="400" />
    <param name="fixed_frame" type="string" value="base_link" />
  </node>
</launch>

On Tue, Jul 27, 2010 at 6:07 PM, Tully Foote <tfoote@willowgarage.com> wrote:
> Hai,
> The tf library is not robust to time jumping backwards.  The first time you
> playback it will work, but the second time time the incoming data will be
> older than the tf buffer and be tossed on on
> reciept. http://www.ros.org/wiki/tf/Errors%20explained#Error:_TF_OLD_DATA
> Tully
>
> On Tue, Jul 27, 2010 at 12:35 PM, Hai Nguyen <haidai@gmail.com> wrote:
>>
>> Hi,
>> Hi,
>>
>> I'm trying to assemble some laser scans into a point cloud using
>> laser_assembler tutorial [1] but the periodic_snapshotter keeps
>> reporting that it is only publishing empty messages with zero points:
>>    [ INFO] [1280258736.674914761, 1275001489.217034967]: Published
>> Cloud with 0 points
>>
>> On closer investigation this seems to be caused by a TF_OLD_DATA error
>> generated by scan_assembler.  Is there a recent change to how the time
>> mechanism works in ROS?  I'm running all these nodes on the same
>> computer, using --clock with "rosbag play" (on the provided bag file
>> laser.bag), and tried to run with /use_sim_time=True but the error
>> still persist.
>>
>> TF error:
>> Node: /scan_assembler
>> Time: 1275001492.698066055
>> Severity: Warn
>> Location:
>> /opt/ros/cturtle/stacks/geometry/tf/src/tf.cpp:Transformer::setTransform:179
>> Published Topics: /rosout
>>
>> TF_OLD_DATA ignoring data from the past for frame /sensor_mount_link
>> at time 1.275e+09 according to authority /play_1280258731455287347
>> Possible reasons are listed at
>>
>> My launch file for laser_assembler:
>> <launch>
>> <node pkg="laser_assembler" type="point_cloud_assembler"
>> name="scan_assembler">
>>    <remap from="scan" to="tilt_scan"/>
>>    <param name="fixed_frame" value="base_footprint"/>
>> </node>
>> </launch>
>>
>>
>>
>> [1]
>> http://www.ros.org/wiki/laser_assembler/Tutorials/HowToAssembleLaserScans
>> --
>> Hai Nguyen
>> CS, Robotics
>> _______________________________________________
>> ros-users mailing list
>> ros-users@code.ros.org
>> https://code.ros.org/mailman/listinfo/ros-users
>
>
>
> --
> Tully Foote
> Systems Engineer
> Willow Garage, Inc.
> tfoote@willowgarage.com
> (650) 475-2827
>
> _______________________________________________
> ros-users mailing list
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>
>



--
Hai Nguyen
CS, Robotics