unable to find the correct transform between odom and base_link for a mobile robot

edit

Hi, This must be a simple problem, but I somehow messed up. I am trying to move pioneer P2DX in Gazebo from say (-5,0) to (5,0). The robot is fitted with two lidars facing 180 deg apart, at two different ends. The important part of the model is below.

  <model name="pioneer2dx_with_lidars">

<include>
  <uri>model://pioneer2dx</uri>
  <pose>0 0 0 0 0 0</pose>
</include>

<include>
  <uri>model://hokuyo_a</uri>
  <name>hokuyo_1</name>
  <pose>0.2 0 0.30 0 0 0</pose>
</include>

<include>
  <uri>model://hokuyo_b</uri>
  <name>hokuyo_2</name>
  <pose>-0.2 0 0.30 0 0 3.14159</pose>
</include>

<joint name="joint1" type="fixed">
  <child>hokuyo_1::link</child> 
  <parent>pioneer2dx::chassis</parent>
</joint> 

<joint name="joint2" type="fixed">
  <child>hokuyo_2::link</child> 
  <parent>pioneer2dx::chassis</parent>
</joint>

</model>

Then, I created a world with other objects along with this robot model. The initial position of the robot was set at (-5,0). Then, I use this package for merging two scans . map was not available initially. So, I wrote a node with br.sendTransform( tf::StampedTransform( tf::Transform(q1, tf::vec(x, y, msg->pose.pose.position.z)), ros::Time::now(), "map", "pioneer2dx_with_lidars/odom")); as well as sendTransform between base_link and the two scanners. The tf tree is given as

(left part is important here).

The tf in the rviz looks like The problem is that although odometry is good but positions of parents in tftree, show incorrect value. The base_link is separated from odom by huge distance and base_link position is showing to be close to -10 just after starting whereas, it should be close to -5. The merged pointcloudis shown in sky blue. Both seems to move along with odom and base_link.

Any help is highly appreciated.