How to change turtlebot gazebo FOV and make it 270 degree?

Hi! I am trying to change the settings of turtlebot simulation, so I can get a better gmapping result. But I can't find a better way to change FOV of kinect. Any help is much appreciated. I went to the turtlebot_description folder and find the urdf file of turtlebot_gazebo.urdf.xarco. I modified the following code. ${60.0*M_PI/180.0} I edited horizontal_fov to change its FOV. If I change it like {160.0*M_PI/180.0}, the result of gmapping can be shown on rviz tool; but if I change horizontal_fov to more than {180.0*M_PI/180.0}, the gmapping result will not be shown. I have been looking everywhere but I can't find where I can remove the restriction and make simulated Kinect have a FOV of 270 degree. I wonder if there is a solution? Thank you very much for helping.