MRU Transform

This ROS node listens to Motion Reference Unit topics and publishes transforms to /tf. Odometry is also published.

Multiple sensors can be configured in a priority list and the node can fallback to secondary sensors if the primary one stops providing data.

This node is designed for integrated sensors that combine a GPS with an IMU to provide complete position and attitude solutions.

Sensor topics

Each sensor is expected to publish on three topics:

• position: sensor_msgs/msg/NavSatFix
• orientation: sensor_msgs/msg/Imu
• velocity: geometry_msgs/msg/PoseWithCovarianceStamped

Only the linear component of the velocity message is used. It describes velocity of the sensor in an ENU frame. The frame_id should reflect the sensor's frame.

Frames

A map frame is created centered on the first position fix. An earth frame is also created and a transformation from ECEF to ENU used by the map frame is published. A null transformation from map to odom is also published. Finally, a transformation from odom to base_link is published with each sensor update.

Additional frames are published which may be useful in special cases, such as a sensor that publishes data that is already corrected for pitch and roll. The base_link_north_up represents a frame at the base_link location without any orientation applied. A level frame with only heading applied is also published as base_link_level.

Parameters

~sensors

A list of sensors which will be used in order. Each sensor entry has a name and a map of topics.

/**:
  ros__parameters:
    # you must "forward declare" the sensors so they can declare 
    # their sub params
    sensor_names:
    - posmv
    - gps
    # then configure the actual sensors
    sensors:
      posmv:
        topics:  
          position: 'sensors/posmv/position'
          orientation: 'sensors/posmv/orientation'
          velocity: 'sensors/posmv/velocity'
      gps:
        topics: 
          position: 'sensors/gps/position'
          orientation: 'sensors/heading' 
          velocity: 'sensors/gps/velocity'

If no sensors are found, a default sensor will be created with topics position, orientation and velocity.

~base_frame, ~map_frame and ~odom_frame

Override the frame_id's which default to base_link, map and odom.

~odom_topic

The topic used to publish odometry messages. Defaults to odom.

Credits

Originally Developed by: Roland Arsenault, University of New Hampshire Center for Coastal and Ocean Mapping

ROS2 migration: Dr. Kristopher Kransosky, Seaward Science