robot_localization asking for map to odom transform

edit

A more appropriate answer to this issue is that, there is a mismatch in timestamps between when the ekf_localization is making that map->odom transform available and when the package is requesting for the same transform.

This solves the issue : We need to tell robot_localization package to publish the transform T seconds into the future so that the next iteration of fusion can use it where T depends on frequency of the robot_localization package. We used the transform time offset parameter to introduce this offset in the timestamps published by the robot_localization node. The new tf_tree after introducing the offset should reflect this change. In our case :

<?xml version="1.0"?>
<launch>

  <arg name="id" default="0"/> 

  <node pkg="robot_localization" type="ekf_localization_node" name="ekf" output="screen" > 

    <!-- Frequency of the main run loop. -->
    <param name="frequency" value="50"/>
    <!-- <param name="sensor_timeout" value="0.1"/> -->
    <!-- <param name="transform_timeout" value="0.1"/> -->
    <param name="odom_frame" value="base_link_origin"/>
    <param name="base_link_frame" value="base_link"/>
    <param name="world_frame" value="world"/>
    <param name="map_frame" value="world"/>
    <param name="two_d_mode" value="false"/>
    <param name="print_diagnostics" value="true"/>
    <param name="publish_tf" value="true"/>
    <param name="transform_time_offset" value="0.05"/> 

    <remap from="odometry/filtered" to="odometry/filtered"/>

    <!-- If the odometry provides both position and linear velocity, fuse the linear velocity.If the odometry provides both orientation angular velocity, fuse the orientation. -->

    <param name="odom0" value="tracker_odom"/>                           
    <rosparam param="odom0_config">[true, true,true,                <!-- x, y, z position -->
                                    false, false, true,                <!-- roll, pitch, yaw angles-->
                                    true, true, true,                   <!-- x/y/z velocity -->
                                    true, true, true,                   <!-- roll/pitch/yaw velocity -->
                                    false, false, false]</rosparam>     <!-- Acceleration -->
    <param name="odom0_differential" value="false"/>
    <param name="odom0_relative" value="false"/>

    <param name="odom1" value="jv_pose_new"/>
    <rosparam param="odom1_config">[true,  true,  true,
                                  false, true, true,
                                  false, false, false,
                                  false, false, false,
                                  false, false, false]</rosparam>
    <param name="odom1_differential" value="false"/>
    <param name="odom1_relative" value="false"/>



     <rosparam param="process_noise_covariance">[0.5, 0,    0,    0,    0,    0,    0,     0,     0,    0,    0,    0,    0,    0,    0,
                           0,    0.5, 0,    0,    0,    0,    0,     0,     0,    0,    0,    0,    0,    0,    0,
                           0,    0,    0.6, 0,    0,    0,    0,     0,     0,    0,    0,    0,    0,    0,    0,
                           0,    0,    0,    0.3, 0,    0,    0,     0,     0,    0,    0,    0,    0,    0,    0,
                           0,    0,    0,    0,    0.3, 0,    0,     0,     0,    0,    0,    0,    0,    0,    0,
                           0,    0,    0,    0,    0,    0.6, 0,     0,     0,    0,    0,    0,    0,    0,    0,
                           0,    0,    0,    0,    0,    0,    0.25, 0,     0,    0,    0,    0,    0,    0,    0,
                           0,    0,    0,    0,    0,    0,    0,     0.25, 0,    0,    0,    0,    0,    0,    0,
                           0,    0,    0,    0,    0,    0,    0,     0,     0.4, 0,    0,    0,    0,    0,    0,
                           0,    0,    0,    0 ...