RobotLocalization: navsatnode give wrong results with "nan covariance"

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<launch>

<node pkg="nostop_robot_localization" type="navsat_transform_node" name="test_navsat_node" respawn="true">

  <param name="magnetic_declination_radians" value="2.38"/>
  <param name="yaw_offset" value="0"/>
  <param name="delay" value="0"/>
  <param name="map_frame" value="SRworld"/>
  <param name="odom_frame" value="odom"/>
   <param name="base_link_frame" value="base_link"/>
   <param name="world_frame" value="SRworld"/>
   <!--  Placeholder for input topic remapping-->
   <!--remap from="don't touch" to="my_topic" /-->
  <remap from="/imu/data" to="/test_imu" />
  <remap from="/gps/fix" to="/test_gps" />
  <remap from="/odometry/filtered" to="/output_of_ekf1" />

   <!-- Placeholders for output remapping. -->
  <remap from="/odometry/gps" to="/odometry_from_gps"/>
  <remap from="/gps/filtered" to="/gps_filtered"/>

</node>

</launch>

This code returns a nan covariance and the transform doesn't work. Imu data, gps data and odometry data are ok. Frames are correctly choose, then where is the problem?

Bag file : https://drive.google.com/open?id=0B_1... Message screenshot : https://drive.google.com/open?id=0B_1...