Hello,

You are assuming that you have 1 ray per angle. But it depends on how you have defined your plugin in the URDF. For example in the following hokuyo plugin you will have 720 samples <samples>720</samples> between -90º <min_angle>-1.570796</min_angle> and 90º <max_angle>1.570796</max_angle>.

<gazebo reference="base_laser_link">
    <sensor type="gpu_ray" name="head_hokuyo_sensor">
        <pose>0 0 0 0 0 0</pose>
        <visualize>true</visualize>
        <update_rate>40</update_rate>
        <ray>
            <scan>
                <horizontal>
                    <samples>720</samples>
                    <resolution>1</resolution>
                    <min_angle>-1.570796</min_angle>
                    <max_angle>1.570796</max_angle>
                </horizontal>
                <vertical>
                    <samples>1</samples>
                    <resolution>1</resolution>
                    <min_angle>0</min_angle>
                    <max_angle>0</max_angle>
                </vertical>
            </scan>
            <range>
                <min>0.10</min>
                <max>30.0</max>
                <resolution>0.01</resolution>
            </range>
            <noise>
            <type>gaussian</type>
                <mean>0.0</mean>
                <stddev>0.01</stddev>
            </noise>
      </ray>
      <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_gpu_laser.so">
        <topicName>/base_scan</topicName>
        <frameName>base_laser_link</frameName>
      </plugin>
    </sensor>
</gazebo>