spawn a map in sdf file

edit

I think you mean spawn gazebo world not the map. This is how i do to start my world in gazebo.

<launch>
      <!-- Arguments -->
      <arg name="paused" default="false"/>
      <arg name="use_sim_time" default="true"/>
      <arg name="gui" default="true"/>
      <arg name="headless" default="false"/>
      <arg name="debug" default="false"/>
      <arg name="world_name" value="$(find your_package)/worlds/your_world"/>

      <!-- Launch Gazebo with the specified world -->
      <include file="$(find gazebo_ros)/launch/empty_world.launch">
        <arg name="debug" value="$(arg debug)" />
        <arg name="gui" value="$(arg gui)" />
        <arg name="paused" value="$(arg paused)"/>
        <arg name="use_sim_time" value="$(arg use_sim_time)"/>
        <arg name="headless" value="$(arg headless)"/>
        <arg name="world_name" value="$(arg world_name)"/>
      </include>
 ...