px4-firmware/launch/mavros_posix_sitl.launch

<launch>
    <!-- MAVROS posix SITL environment launch script -->

    <arg name="headless" default="false"/>
    <arg name="gui" default="true"/>
    <arg name="ns" default="/"/>
    <arg name="world" default="iris"/>
    <arg name="build" default="posix_sitl_default"/>
    <arg name="fcu_url" default="udp://:14540@localhost:14557"/>

    <include file="$(find px4)/launch/posix_sitl.launch">
        <arg name="headless" value="$(arg headless)"/>
        <arg name="gui" value="$(arg gui)"/>
        <arg name="ns" value="$(arg ns)"/>
        <arg name="world" value="$(arg world)"/>
        <arg name="build" value="$(arg build)"/>
    </include>

    <include file="$(find px4)/launch/mavros.launch">
        <arg name="ns" value="$(arg ns)"/>
        <arg name="gcs_url" value=""/> <!-- GCS link is provided by SITL -->
        <arg name="fcu_url" value="$(arg fcu_url)"/>
    </include>
</launch>