Is it normal to get these errors using Madgwick filter?

[faustodidomenico]

Hello, I'm trying to estimate the orientation using Madgwick filter in a simulated rosbag created with Gazebo, but the estimation has some errors compared to the ground-truth. I compare the results using https://github.com/MichaelGrupp/evo. Here is the graphic of the error in degrees:

I tried with different configurations and parameters values but this is the best I could get. As we can see, it has a maximum error of 8.8° and a mean of 4.2°. Is it normal to get these errors? or should it be something more precise?

The IMU is simulated with the Intel RealSense Gazebo ROS plugin (https://github.com/pal-robotics/realsense_gazebo_plugin) and the magnetometer with Hector Gazebo Ros Magnetic plugin (https://github.com/tu-darmstadt-ros-pkg/hector_gazebo)
The sensor configuration:

<sensor name="${camera_name}imu" type="imu">
        <always_on>true</always_on>
        <update_rate>${gyro_fps}</update_rate>
        <topic>${camera_name}/imu/sample</topic>
        <plugin name="${camera_name}imu" filename="libgazebo_ros_imu_sensor.so">
          <topicName>${camera_name}/imu/sample</topicName>
          <bodyName>${camera_name}_link</bodyName>
          <frameName>${gyro_optical_frame}</frameName>
          <updateRateHZ>${gyro_fps}</updateRateHZ>
          <gaussianNoise>0.0</gaussianNoise>
          <xyzOffset>0 0 0</xyzOffset>
          <rpyOffset>0 0 0</rpyOffset>
          <!-- Nota(Dante): añadido ver http://gazebosim.org/tutorials?tut=ros_gzplugins#IMU(GazeboRosImu) -->
          <initialOrientationAsReference>false</initialOrientationAsReference>
        </plugin>
      </sensor>
    </xacro:if>
    <!-- Accel and gyro -->
    <xacro:unless value="${unite_imu_method == 'copy' or unite_imu_method == 'linear_interpolation'}">
      <sensor name="${camera_name}accel" type="imu">
        <always_on>true</always_on>
        <update_rate>${accel_fps}</update_rate>
        <topic>${camera_name}/accel/sample</topic>
        <plugin name="${topics_ns}_accel_plugin" filename="librealsense_gazebo_accel_sensor.so">
          <topicName>${camera_name}/accel/sample</topicName>
          <bodyName>${camera_name}_link</bodyName>
          <updateRateHZ>${accel_fps}</updateRateHZ>
          <gaussianNoise>0.0</gaussianNoise>
          <xyzOffset>0 0 0</xyzOffset>
          <rpyOffset>0 0 0</rpyOffset>
          <frameName>${accel_optical_frame}</frameName>
          <initialOrientationAsReference>false</initialOrientationAsReference>
        </plugin>
        <pose>0 0 0 0 0 0</pose>
      </sensor>
      <sensor name="${camera_name}gyro" type="imu">
        <always_on>true</always_on>
        <update_rate>${gyro_fps}</update_rate>
        <topic>${camera_name}/gyro/sample</topic>
        <plugin name="${topics_ns}_gyro_plugin" filename="librealsense_gazebo_gyro_sensor.so">
          <topicName>${camera_name}/gyro/sample</topicName>
          <bodyName>${camera_name}_link</bodyName>
          <updateRateHZ>${gyro_fps}</updateRateHZ>
          <gaussianNoise>0.0</gaussianNoise>
          <xyzOffset>0 0 0</xyzOffset>
          <rpyOffset>0 0 0</rpyOffset>
          <frameName>${gyro_optical_frame}</frameName>
          <initialOrientationAsReference>false</initialOrientationAsReference>
        </plugin>

<plugin name="hector_magnetometer" filename="libhector_gazebo_ros_magnetic.so">
      <bodyName>magnetometer_link</bodyName>
      <frameId>magnetometer_link</frameId>
      <topicName>magnetometer/fix</topicName>
      <updateRate>300.0</updateRate>
      <referenceHeading>90</referenceHeading>
      <declination>-8.5985</declination>
      <inclination>-37.8919</inclination>
      <magnitude>22.5782e-06</magnitude>
      <gaussianNoise>0 0 0</gaussianNoise>
      <useMagneticFieldMsgs>true</useMagneticFieldMsgs>
      <useWorldSphericalCoordinates>false</useWorldSphericalCoordinates>
    </plugin>