RTAB slam

I wanted to perform slam using RTAB map. Is it possible to create a map of an unknown environment and localize within without any prebuilt map with the help of RTAB?

[matlabbe]

It is the default mode of RTAB-Map, it will do SLAM by default.

In that case, my robot is building map of the environment and is incrementing. How do I know if my robot is able to localize in the environment or get the pose of the rover respective to global reference frame?

[aninath93]

When you set below parameters, you will see on /info topic not being null to know if the robot has localized or not.

            'Mem/IncrementalMemory','false',
            'Mem/InitWMWithAllNodes','true',

I have written a launch file for SLAM which is here below. With this launch file, I am able to build the map but how do I get the real time pose of the robot if it is localizing simultaneously? Also, is it the correct approach to do SLAM?

<?xml version="1.0" encoding="UTF-8"?>
<launch>

  <!-- Choose visualization -->
  <arg name="rtabmapviz"              default="false" />
  <arg name="rviz"                    default="true" />

  <!-- Localization-only mode -->
  <arg name="localization"            default="true"/>
  
  
  <arg name="pi/2" value="1.5707963267948966" />
  <arg name="optical_rotate" value="0 0 0 -$(arg pi/2) 0 -$(arg pi/2)" />
  <node pkg="tf" type="static_transform_publisher" name="camera_base_link"
     args="$(arg optical_rotate) chassis camera 100" />  

<!-- CONFIG FOR ROBOT1 -->
  <group ns="robot1/stereo" >
    <node pkg="stereo_image_proc" type="stereo_image_proc" name="stereo_image_proc"/>

    <!-- Odometry -->
    <node pkg="rtabmap_odom" type="stereo_odometry" name="stereo_odometry" output="screen">
        <remap from="left/image_rect"       to="left/image_rect"/>
        <remap from="right/image_rect"      to="right/image_rect"/>
        <remap from="left/camera_info"      to="left/camera_info"/>
        <remap from="right/camera_info"     to="right/camera_info"/>

        <param name="frame_id" type="string" value="chassis"/>
        <param name="odom_frame_id" type="string" value="odom"/>
        <param name="approx_sync"   type="bool" value="false"/>
        <param name="queue_size"    type="int" value="5"/>

        <param name="Odom/MinInliers" type="string" value="12"/>
        <param name="Odom/RoiRatios"  type="string" value="0.03 0.03 0.04 0.04"/>
    </node>     
  </group>

  <group ns="rtabmap">   
    <node name="rtabmap" pkg="rtabmap_slam" type="rtabmap" output="screen" args=""> <!--	delete_db_on_start-->
     <param name="frame_id" type="string" value="chassis"/>
     <param name="subscribe_stereo" type="bool" value="true"/>
     <param name="subscribe_depth"  type="bool" value="false"/>
     <param name="approx_sync"      type="bool" value="false"/>
    
     
     <remap from="left/image_rect"   to="/robot1/stereo/left/image_rect_color"/>
     <remap from="right/image_rect"  to="/robot1/stereo/right/image_rect"/>
     <remap from="left/camera_info"  to="/robot1/stereo/left/camera_info"/>
     <remap from="right/camera_info" to="/robot1/stereo/right/camera_info"/>

     <remap from="odom" to="/robot1/stereo/odom"/>

     <param name="queue_size" type="int" value="30"/>
     <param name="Vis/MinInliers" type="string" value="12"/>
     
   <!-- Enable localization in mapping mode -->
     <param name="Mem/IncrementalMemory" type="bool" value="true"/>
     <param name="Mem/InitWMWithAllNodes" type="string" value="$(arg localization)"/>
      
    </node>
  </group>
 


 <!-- Visualisation RVIZ --> 
   <node if="$(arg rviz)" pkg="rviz" type="rviz" name="rviz" args="-d $(find rtabmap_demos)/launch/config/demo_stereo_outdoor.rviz"/> 
   
</launch>

[matlabbe]

You can get use localization_pose to have a pose topic in map frame. However, if you need faster pose in map frame, consider subscribing to odometry topic, then use TF to transform the odometry pose in map frame.