Robotics - ROS2 TF2

TF2 and Sim Time

When working with ROS2 and tf2, you may encounter the following warning when visualizing data in RViz or processing buffers:

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Warning: TF_OLD_DATA ignoring data from the past for frame base_link at time 4.294967 according to authority Authority undetectable

This message indicates that tf2 is dropping out-of-order or stale transforms because your TF publisher is using a “simulated time” (or older timestamps), while the receiver uses the default system clock. In that case, we need to run nodes using use_sim_time

• One example is replaying a bag and displaying on rviz. ros2 run rviz2 rviz2 --ros-args -p use_sim_time:=true

In your tf publisher node:

1. Enable Sim Time Parameter. In your node’s constructor or setup, set:

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node_->set_parameter(rclcpp::Parameter("use_sim_time", true));

1. Create a Clock Publisher. Declare and initialize a publisher for rosgraph_msgs::msg::Clock:

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rclcpp::Publisher<rosgraph_msgs::msg::Clock>::SharedPtr clock_pub_;
clock_pub_ = node_->create_publisher<rosgraph_msgs::msg::Clock>("/clock", 10);

1. Publish clock and tf together:

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// Build and publish clock
rosgraph_msgs::msg::Clock clk;
clk.clock = imu_msg->header.stamp;  // reuse the IMU’s timestamp
clock_pub_->publish(clk);
imu_tf_publisher_->publish(*imu_msg);

Transform Listener

Life Cycle

• tf2_ros::TransformListener starts its own subscription /tf, /tf_static:
  1. node_->create_subscription<tf2_msgs::msg::TFMessage>( … )
  2. stores that subscription in the same callback group / executor your node is using, and

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