Consistent handling of tf_prefix

[saschroeder]

The tf_prefix is not used consistently in the current implementation. The only case, where it is actually resolved is
https://github.com/ros-perception/slam_gmapping/blob/5a707e079364ab9f5349c72310f31bfed4a6c834/gmapping/src/slam_gmapping.cpp#L765
so the frame id of the published maps actually includes the prefix, while the transforms of the map frame are published without the prefix:
https://github.com/ros-perception/slam_gmapping/blob/b916ea23f71fe73593f503810b0a1c59aa0481d8/gmapping/src/slam_gmapping.cpp#L802
So it's not possible to visualize the resulting map if using tf_prefix.

The two possible solutions are: 1) don't use the tf_prefix at all 2) use it consistently (including also the base, scan and odom frame)

If someone knows another solution to use gmapping when the tf_prefix is set, I would appreciate this, too.

[ybgdgh]

I think you can still use the tf_prefix, but change absolute frame names for all the frames Gmapping needs, such as

    <param name="odom_frame" value="/$(arg robot_name)/odom"/>
    <param name="base_frame" value="/$(arg robot_name)/base_link"/>
    <param name="map_frame" value="/$(arg robot_name)/map"/>

in the main launch file, you can use tf_prefix normally:

  <group ns="/robot_1">
      <param name="tf_prefix" value="robot_1" />
      <include file="$(find jackal_gazebo)/launch/spawn_jackal.launch">
        <arg name="x" value="0" />
        <arg name="y" value="0" />
        <arg name="z" value="0.0" />
        <arg name="yaw" value="0" />
        <arg name="config" value="$(arg config)" />
        <arg name="joystick" value="$(arg joystick)" />
        <arg name="robot_name" value="robot_1"/>
      </include>
      <include file="$(find jackal_navigation)/launch/include/multi_map_move.launch">
        <arg name="robot_name" value="robot_1"/>
      </include> 
  </group>

when you use absolute frame names, you can change anything you want, and don't need to change the source code. Hope this can help you.