Put static tf nodes under ns group

launch/wheel_static_transform.launch

@@ -3,24 +3,28 @@
 
   <arg name="ns" default="pioneer3"/>
 
-  <node pkg="tf"
-        type="static_transform_publisher"
-        name="static_tf_front_left_wheel"
-        args=" 0.135  0.156 0.111 0 0 0       /$(arg ns)/base_link /$(arg ns)/front_left_axle  10"/>
-  
-  <node pkg="tf"
-        type="static_transform_publisher"
-        name="static_tf_front_right_wheel"
-        args=" 0.135 -0.156 0.111 0 0 3.14159 /$(arg ns)/base_link /$(arg ns)/front_right_axle 10"/>
-  
-  <node pkg="tf"
-        type="static_transform_publisher"
-        name="static_tf_rear_left_wheel"
-        args="-0.135  0.156 0.111 0 0 0       /$(arg ns)/base_link /$(arg ns)/rear_left_axle   10"/>
-  
-  <node pkg="tf" 
-        type="static_transform_publisher" 
-        name="static_tf_rear_right_wheel"
-        args="-0.135 -0.156 0.111 0 0 3.14159 /$(arg ns)/base_link /$(arg ns)/rear_right_axle  10"/>
-
-</launch>
\ No newline at end of file
+  <group ns="$(arg ns)">
+
+    <node pkg="tf"
+          type="static_transform_publisher"
+          name="static_tf_front_left_wheel"
+          args=" 0.135  0.156 0.111 0 0 0       /$(arg ns)/base_link /$(arg ns)/front_left_axle  10"/>
+
+    <node pkg="tf"
+          type="static_transform_publisher"
+          name="static_tf_front_right_wheel"
+          args=" 0.135 -0.156 0.111 0 0 3.14159 /$(arg ns)/base_link /$(arg ns)/front_right_axle 10"/>
+
+    <node pkg="tf"
+          type="static_transform_publisher"
+          name="static_tf_rear_left_wheel"
+          args="-0.135  0.156 0.111 0 0 0       /$(arg ns)/base_link /$(arg ns)/rear_left_axle   10"/>
+
+    <node pkg="tf"
+          type="static_transform_publisher"
+          name="static_tf_rear_right_wheel"
+          args="-0.135 -0.156 0.111 0 0 3.14159 /$(arg ns)/base_link /$(arg ns)/rear_right_axle  10"/>
+
+  </group>
+
+</launch>