to run the simulation use the following commands
$ roscore
$ catkin_make
$ source devel/setup.bash
$ roslaunch turtlebot3_gazebo turtlebot3_world.launch
$ source devel/setup.bash
$ roslaunch my_rtabmap mapping_turtlebot3.launch
to run the simulation use the following commands
$ roscore
$ catkin_make
$ source devel/setup.bash
$ roslaunch turtlebot3_gazebo turtlebot3_world.launch
$ source devel/setup.bash
$ roslaunch my_rtabmap mapping_turtlebot3.launch