Odometry launch script

<!--
  Launcher for differential drive wheel odometry.
  Change the encoder serial numbers as needed.  The serial numbers can be viewed by running:
      rosrun phidgets manager
  This requires:
      2 x Phidgets high speed encoder
      A known number of encoder counts per millimetre of travel for each wheel
  -->
<launch>
    <!-- phidgets high speed encoders -->
    <node pkg="phidgets" type="high_speed_encoder" name="encoder_left" respawn="true">
        <!-- phidget device serial number for the left encoder -->
        <param name="serial" value="351547" />
    </node>
    <node pkg="phidgets" type="high_speed_encoder" name="encoder_right" respawn="true">
        <!-- phidget device serial number for the right encoder -->
        <param name="serial" value="351673" />
    </node>
    <!-- odometry -->
    <node pkg="phidgets" type="odometry" name="odometry" respawn="true" output="screen">
        <!-- phidget device serial numbers for the left and right encoders -->
        <param name="serialleft" value="351547" />
        <param name="serialright" value="351673" />
        <!-- separation between the two wheels in millimeters (11 5/32 inches or 283)-->
        <!-- half the wheelbase works  -->
        <param name="wheelbase" value="141" />
        <!-- number of encoder counts per millimetre for the left wheel -->
        <param name="countspermmleft" value="6" />
        <!-- number of encoder counts per millimetre for the right wheel -->
        <param name="countspermmright" value="6" />
        <!-- whether to show additional info -->
        <param name="verbose" value="true" />
    </node>
</launch>