<sdf version='1.5'>
  <world name='default'>
    <!-- include sun and ground plane -->
    <include><uri>model://sun</uri></include>
    <include><uri>model://ground_plane</uri></include>

    <model name="sensor_box">
      <static>true</static>
      <link name="link">
        <pose>0 0 0.251  0 0 0</pose>
        <collision name="collision">
          <geometry>
            <box>
              <size>4 4 0.5</size>
            </box>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <box>
              <size>4 4 0.5</size>
            </box>
          </geometry>
          <material><script>
            <uri>file://media/materials/scripts/gazebo.material</uri>
            <name>Gazebo/Grey</name>
          </script></material>
        </visual>
        <collision name="collision2">
          <pose>0 0 1 0 0 0</pose>
          <geometry>
            <box>
              <size>4 4 0.5</size>
            </box>
          </geometry>
        </collision>
        <visual name="visual2">
          <pose>0 0 1 0 0 0</pose>
          <geometry>
            <box>
              <size>4 4 0.5</size>
            </box>
          </geometry>
          <material><script>
            <uri>file://media/materials/scripts/gazebo.material</uri>
            <name>Gazebo/Grey</name>
          </script></material>
        </visual>
        <sensor name="box_contact" type="contact">
          <always_on>true</always_on>
          <update_rate>1000</update_rate>
          <contact>
            <collision>collision</collision>
          </contact>
        </sensor>
        <sensor name="box_contact2" type="contact">
          <always_on>true</always_on>
          <update_rate>1000</update_rate>
          <contact>
            <collision>collision2</collision>
          </contact>
        </sensor>
      </link>
    </model>

  </world>
</sdf>
