Re: Multi-Mapping with rtabmap , how to?

Posted by matlabbe on
URL: http://official-rtab-map-forum.206.s1.nabble.com/Multi-Mapping-with-rtabmap-how-to-tp202p209.html

Hi Alex,

1)
We made multiple databases for convenience, we could have created only one. The databases were created from these 5 ROS bags (RGBD images are recorded at 10Hz using data_throttle). Between the recording of each ROS bag, the robot controller is restarted to reinitialize the odometry (giving the identity pose for the first image). When RTAB-Map detects an Identity pose, it automatically creates a new map. Here the command used to record the ROS bags on our robot (images are saved compressed to save space):

  <!-- Throttling OpenNI messages (using nodelet manager of OpenNI)-->
  <group ns="camera">
    <node pkg="nodelet" type="nodelet" name="data_throttle" args="load rtabmap_ros/data_throttle camera_nodelet_manager">
      <param name="rate" type="double" value="10.0"/>
   
      <remap from="rgb/image_in"       to="rgb/image_rect_color"/>
      <remap from="depth/image_in"     to="depth_registered/image_raw"/>
      <remap from="rgb/camera_info_in" to="depth_registered/camera_info"/>
    
      <remap from="rgb/image_out"       to="data_throttled_image"/>
      <remap from="depth/image_out"     to="data_throttled_image_depth"/>
      <remap from="rgb/camera_info_out" to="data_throttled_camera_info"/>
    </node>   
  </group>

$ rosbag record camera/data_throttled_image/compressed camera/data_throttled_image_depth/compressedDepth camera/data_throttled_camera_info tf base_scan /base_controller/odom

If you want to convert the ROS bags to RTAB-Map database format using data_recorder, you can play them while having the data_recorder launched like this (so they can be played in the standalone version like in the multi-session tutorial):

  <node name="data_recorder" pkg="rtabmap_ros" type="data_recorder">
	<param name="output_file_name" value="output_record.db" type="string"/>  
	
	<param name="frame_id" type="string" value="base_footprint"/>
	
	<param name="subscribe_odometry" type="bool" value="true"/>
	<param name="subscribe_depth" type="bool" value="true"/>
	<param name="subscribe_laserScan" type="bool" value="true"/>
	
	<remap from="odom" to="/base_controller/odom"/>
	<remap from="scan" to="/base_scan"/>

	<remap from="rgb/image" to="camera/data_throttled_image"/>
  	<remap from="depth/image" to="camera/data_throttled_image_depth"/>
  	<remap from="rgb/camera_info" to="camera/data_throttled_camera_info"/>

        <param name="rgb/image_transport" type="string" value="compressed"/>
     	<param name="depth/image_transport" type="string" value="compressedDepth"/> 
  	
	<param name="queue_size" type="int" value="10"/>
  </node>

2)
Which referential is taken is defined by "RGBD/OptimizeFromGraphEnd" parameter:
"Optimize the graph from the newest node. If false, the graph is optimized from the oldest node of the current graph (this adds an overhead computation to detect to oldest node of the current graph, but it can be useful to preserve the map referential from the oldest node). Warning when set to false: when some nodes are transferred, the first referential of the local map may change, resulting in momentary changes in robot/map position (which are annoying in teleoperation)."
When set to true, the map is corrected instead the odometry position, assuming that the current robot position is the root of the graph. This is explained in Section II-B of this paper.

4)
rtabmap node is always multi-session. Adding argument "delete_db_on_start" makes deleting the database on start. If the database is not deleted, a new map is automatically created in the loaded database and will be merged to an old map in the database when a loop closure is detected (with a location in a previous map). You can effectively use always the same database (with multiple maps inside). To initiate manually a new map without closing the rtabmap node, you can call service "/rtabmap/trigger_new_map".

5)
In RVIZ, you can only visualize the edges of the current graph (without the vertices) using rtabmap/MapGraph display plugin.

Regards,
Mathieu