Trouble exporting map from RTAB-Map

[rakshak]

I am following this answer to export a .pgm and a .yaml from a database file generated using RTAB-map.

But when I run

   rosrun rtabmap_ros rtabmap _database_path:=IROS14-kinect-challenge.db

I get a message saying that /rtabmap did not receive any data since 5 seconds. I know there is no data being published into /odom, /rgb/image, /depth/image,/rgb/camera_info but shouldn't this data be coming from the database file?

When I run
   rosrun map_server map_saver map:=proj_map
I get this message
       [ INFO] [1551154609.903198676]: Waiting for the map
and
      rosservice call /publish_map 1 1 0
doesn't do anything.  

I am running ROS melodic on Linux Mint(Ubuntu 18.04).
I have downloaded the IROS14-kinect-challenge.db file from here
I have double checked that roscore is running. :D

[matlabbe]

See https://answers.ros.org/question/316634/trouble-exporting-map-from-rtab-map/

[rakshak]

Thanks for responding, ill reply on the ros answers page.