i folloed book "learn ros for robotics programming second edition".and i use slam gmapping to build map.i move my robot in gazebo with skidsteer plugnin and no odometry and map received at RVIZ.and there is also no tf between base_link and odom.where is issue. here is my launch file and skid steer plugin code..plz help me

launch File <?xml version="1.0"?> <!-- this launch file corresponds to robot model in ros-pkg/robotdescriptions/pr2/erraticdefs/robots for full erratic -->

<!-- start up wg world -->

<!-- start robot state publisher -->

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

Skid Steer plugin in my xacro file

100.0 / basetowheel1 basetowheel3 basetowheel2 basetowheel4 4 0.1 baselink 1 navmsgs basefootprint odom cmdvel 0