How to choose the Gaussian noise of a Sensor?

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I am using Velodyne VLP16 Lidar at my simulations. I found the plugin below from here;

    <plugin name="gazebo_ros_laser_controller" filename="libgazebo_ros_velodyne_laser.so">
      <topicName>${ros_topic}</topicName>
      <frameName>${name}_frame</frameName>
      <min_range>0.45</min_range>
      <max_range>130.0</max_range>
      <gaussianNoise>0.008</gaussianNoise>
    </plugin>

And I wonder why Gaussian Noise is set to 0.008 and how can it be measured?

This is the sensor specifications;