How can I see the apriltag offset in ROS

  • Hello!
    I would like to use the Apriltag frame localization over in ROS to localize my drone. However all of the mavros odom topics do not seem to publish this offset. Is there a way to do this? I can see the offsets when I run voxl-vision-px4 -p

  • No response. I'll ask a related question... what is the most stable odom topic that is transmitted in MAVROS? /mavros/local_position/odom seems to have a lot of drift.

  • Dev Team

    The drift might be typical VIO drift. If the lighting is reasonable and there are interesting things to look at, VIO should hold pretty steady. If there is limited lighting/features you will see drift, vibration on the IMU can have significant negative effects on VIO performance as well.

    voxl-vision-px4 does the AprilTag correction internally. It's certainly possible to do this in ROS, it just would require some coding to make it happen.

  • Thanks, so my question is, if I am running a planner in ROS, and sending out move simple goals to a local coordinate, will the vehicle auto correct it's odometry while flying around? My tests seem to suggest that this would not be the case.

  • Dev Team

    In voxl-suite 0.2.0, if voxl-vision-px4 is configured to incorporate the apriltag corrections, it should happen automatically if using VIO from vvpx4 as the odometry source.

    The MPA version of apriltag server will be open and found here and this will work with newer versions of voxl-suite. We're in active development of this now

  • Dev Team

    @kiprock I spoke too soon and was incorrect. There was no way to get "fixed frame" pose in older apriltag implementation either. The fixed frame is published here in the old code, but that would have to be sent to ROS manually.

    We will make sure that fixed frame is published in the upcoming version (hopefully this week), and then it will be available in voxl_mpa_to_ros

    @James-Strawson for awareness

  • That is what I thought. I have not updated the system yet. Please let me know when this update is available!

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