robot_localization: WARNING: could not obtain transform from map to odom. Error was Unable to lookup. Could not transform measurement into odom. Ignoring...

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hello, I have a nomadic scout 2-wheel robot with a kinect sensor that is able to navigate inside a map by means of the ros (groovy) navigation stack. An odometry topic is provided by the robot, and the /odom --> /base_link transform too. I want to feed the ekf_localization node with the position the robot provided by our Vicon MoCap system, in order to fuse it with the odometry information. I have a map, provided by a map server, and the robot pose coming from Vicon is published as a PoseWithCovarianceStamped topic, with ref_frame_id = 'map'. So I want to use ekf_localization node in the second mode, with world_frame = 'map', and I expect the /map --> /odom tf from ekf_localization node. What I see is that ekf_localization node is publishing /odom --> /base_link transform too, overwriting the odometry-generated transform each other. So the ekf_localization node seems working in the first mode, and it does not sense the /odom --> /base_link tf, already published by the robot.

this is my ekf launch file:

<launch>

    <node pkg="robot_localization" type="ekf_localization_node" name="ekf_localization" clear_params="true">

      <param name="frequency" value="30"/>

      <param name="sensor_timeout" value="0.1"/>

      <param name="two_d_mode" value="true"/>

      <param name="pose0" value="/scoutPose"/>

      <param name="odom0" value="/odom"/>

      <rosparam param="pose0_config">[true, true, false, true, true, true, false, false, false, false, false, false]</rosparam>

      <rosparam param="odom0_config">[true, true, false, true, true, true, false, false, false, false, false, false]</rosparam>

      <param name="pose0_differential" value="true"/>

      <param name="odom0_differential" value="false"/>

      <param name="debug" value="true"/>

      <param name="debug_out_file"  value="/home/robouser/debug_ekf_localization.txt"/>

      <param name="map_frame" value="map"/>

      <param name="world_frame" value="map"/>

      <param name="odom_frame" value="odom"/>

      <param name="base_link_frame" value="base_link"/>

      <rosparam param="process_noise_covariance">[0.03, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.03, 0.0, 0.0, 0.0, 0.0, 0.0, 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, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.03, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.0, 0.03, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.0, 0.00, 0.06, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.0, 0.00, 0.0, 0.025, 0.0, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.0, 0.00, 0.0, 0.0, 0.025, 0.0, 0.0, 0.0, 0.0,
                                                  0.0, 0.0, 0.0, 0.0, 0.00, 0.0, 0.0, 0.0, 0.05, 0.0, 0.0, 0.0,
                                                  0.0, 0 ...