When launching rtabmap_ros's nodes, if you have the error error while loading shared libraries..., try ldconfig or add the next line at the end of your ~/.bashrc to fix it:

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/ros/noetic/lib/x86_64-linux-gnu

Build from Source:
The next instructions assume that you have set up your ROS workspace using this tutorial. The workspace path is ~/catkin_ws and your ~/.bashrc contains:

$ source /opt/ros/$ROS_DISTRO/setup.bash

$ source ~/catkin_ws/devel/setup.bash

Install RTAB-Map standalone libraries. Do not clone in your Catkin workspace:

cd ~

git clone https://github.com/introlab/rtabmap.git rtabmap

cd rtabmap/build

cmake ..  [<---double dots included]

make -j6

sudo make install

Install RTAB-Map ros-pkg in your src folder of your Catkin workspace:

cd ~/catkin_ws

git clone https://github.com/introlab/rtabmap_ros.git src/rtabmap_ros

catkin_make -j4

Use catkin_make -j1 if compilation requires more RAM than you have (e.g., some files require up to ~2 GB to build depending on gcc version).

Options:

Add -DRTABMAP_SYNC_MULTI_RGBD=ON to catkin_make if you plan to use multiple cameras.

Add -DRTABMAP_SYNC_USER_DATA=ON to catkin_make if you plan to use user data synchronized topics.

If the folders are not in the workspace as indicated above, follow the instructions below:

In the home directory, clone the Isaac Sim ROS Workspace repo:

git clone https://github.com/isaac-sim/IsaacSim-ros_workspaces

In the terminal, navigate to this directory:

cd /home/mavric-wonse/IsaacSim-ros_workspaces/noetic_ws/src/navigation

Then copy the folders carter_2dnav and carter_description and paste it inside /catkin_urop/src.

Then cd .. and run catkin_make

Navigate to this directory to access the launch file:
/home/mavric-wonse/catkin_urop/src/rtabmap_ros/rtabmap_demos/launch/demo_isaac_carter_navigation.launch

Launch File:
<?xml version="1.0"?>

<launch>

<group ns="rtabmap">

<!-- -->

    <!-- For ref: https://docs.omniverse.nvidia.com/app_isaacsim/app_isaacsim/tutorial_ros_navigation.html#isaac-sim-app-tutorial-ros-navigation

         1) In Isaac sim, click on menu Isaac Examples - ROS - Navigation

         2) Terminal:  $ roscore

         3) To teleop: $ rosrun teleop_twist_keyboard teleop_twist_keyboard.py _speed:=0.15 _turn:=0.20

         4) Navigation: roslaunch rtabmap_demos demo_isaac_carter_navigation.launch

         5) Set max depth range to 10m in rtabmap_viz for correct visualization (Preferences->3D Rendering under map and odom columns)

         6) Press Play in Isaac sim

         Note: carter_2dnav package can be copied to your catkin_ws from:

            $ cp -r ~/.local/share/ov/pkg/isaac_sim-2021.2.0/ros_workspace/src/* ~/catkin_ws/src/.

       Isaac Sim 2021:

         For Lidar 3D Mode (lidar3d:=true), make sure in isaac sim that Carter robot is set with VLP16-like parameters (16 rings):

            Under World -> Carter_ROS -> chassis_link -> carter_lidar -> highLod = True

                                                                      -> verticalFov = 32

                                                                      -> verticalResolution = 2

                                                      -> ROS_lidar    -> pointCloudEnabled = True

       Isaac Sim 2022 (Action Graph):

         To enable all camera streams (right, depth left and depth right):

           1. Stage view -> World-> Carter_ROS, right-click on ROS_Cameras -> Open graph

           2. For all Branch nodes (green/red icon), select them, then check Compute Node -> Inputs -> Condition checkbox.

         3D LIDAR: TODO: didn't find how to enable/publish it.

    -->

    <param name="use_sim_time" value="true" />

    <arg name="localization" default="true" />

    <arg name="lidar3d"             default="true" /> <!-- Best results if rtabmap is built with libpointmatcher -->

    <arg name="lidar3d_ray_tracing" default="true" />

    <arg name="lidar3d_grid3d"      default="true" />

    <arg name="camera"              default="true" />

    <arg name="stereo"              default="false" /> <!-- RGB-D mode by default -->

    <!-- Load Robot Description -->

    <arg name="model" default="/home/mavric-wonse/catkin_urop/src/carter_description/urdf/carter.urdf"/>

    <param name="robot_description" textfile="/home/mavric-wonse/catkin_urop/src/carter_description/urdf/carter.urdf" />

    <!-- Lidar 3D based on demo_husky.launch -->

    <arg     if="$(arg lidar3d)" name="cell_size" default="0.2" />

    <arg unless="$(arg lidar3d)" name="cell_size" default="0.05" />

    <arg     if="$(arg lidar3d)" name="args3d" value="--Icp/Iterations 10 --Icp/PointToPlaneGroundNormalsUp 0.9 --Icp/PointToPlaneRadius 0 --Icp/MaxCorrespondenceDistance 1 --Grid/ClusterRadius 1 --Grid/RangeMax 10 --Grid/RayTracing $(arg lidar3d_ray_tracing) --Grid/CellSize $(arg cell_size) --Mem/LaserScanNormalK 10 --Grid/3D $(arg lidar3d_grid3d)" />

    <arg unless="$(arg lidar3d)" name="args3d" value="--Grid/RangeMax 10" /> <!-- 2d scan, use default params -->

    <!-- RTAB-Map --> 

    <remap from="/rtabmap/grid_map" to="/map"/>

    <include file="/home/mavric-wonse/catkin_urop/src/rtabmap_ros/rtabmap_ros/launch/rtabmap.launch">

        <arg     if="$(arg localization)" name="args" value="--Reg/Strategy 1 --Reg/Force3DoF true --RGBD/NeighborLinkRefining true --Icp/MaxTranslation 0.5 $(arg args3d)"/>

        <arg unless="$(arg localization)" name="args" value="-d --Reg/Strategy 1 --Reg/Force3DoF true --RGBD/NeighborLinkRefining true --Icp/MaxTranslation 0.5 $(arg args3d)"/>

        <arg name="localization"      value="$(arg localization)"/>

        <arg     if="$(arg lidar3d)" name="subscribe_scan_cloud" value="true"/>

        <arg unless="$(arg lidar3d)" name="subscribe_scan" value="true"/>

        <!--<arg name="stereo"            value="$(eval camera and stereo)"/> -->

        <arg name="depth"             value="$(eval camera and not stereo)"/>

        <arg name="subscribe_rgb"     value="$(arg camera)"/>

        <arg name="visual_odometry"   value="false"/>

        <arg name="odom_topic"        value="/odom"/>

        <arg name="frame_id"          value="base_link"/>

        <arg name="depth_topic"       value="/depth_left"/>

        <arg name="rgb_topic"         value="/rgb_left"/>

        <arg name="camera_info_topic" value="/camera_info_left"/>

        <arg name="left_image_topic"        value="/rgb_left"/>

        <arg name="left_camera_info_topic"  value="/camera_info_left"/>

        <arg name="right_image_topic"       value="/rgb_right"/>

        <arg name="right_camera_info_topic" value="/camera_info_right"/>

        <arg name="scan_topic"        value="/scan"/>

        <arg name="scan_cloud_topic"  value="/point_cloud"/>

        <arg name="rgbd_sync"         value="true"/>

        <arg name="approx_rgbd_sync"  value="true"/>

        <arg name="use_sim_time"      value="true"/>

        <arg name="tag_linear_variance" value="0.1"/>

        <arg name="tag_angular_variance" value="0.2"/>

        <arg name="scan_cloud_assembling"             value="$(arg lidar3d)"/>

        <arg name="scan_cloud_assembling_fixed_frame" value="odom"/>

        <arg name="scan_cloud_assembling_range_max"   value="60"/>

        <arg name="scan_cloud_assembling_voxel_size"  value="$(arg cell_size)"/>

    </include>

    <node pkg="move_base" type="move_base" respawn="false" name="move_base" output="screen">

        <param name="TrajectoryPlannerROS/max_vel_theta" value="0.3"/>

        <param name="TrajectoryPlannerROS/min_vel_theta" value="-0.3"/>

        <rosparam file="/home/mavric-wonse/catkin_urop/src/carter_2dnav/params/costmap_common_params.yaml" command="load" ns="global_costmap" />

        <rosparam file="/home/mavric-wonse/catkin_urop/src/carter_2dnav/params/costmap_common_params.yaml" command="load" ns="local_costmap" />

        <rosparam file="/home/mavric-wonse/catkin_urop/src/carter_2dnav/params/local_costmap_params.yaml" command="load" />

        <rosparam file="/home/mavric-wonse/catkin_urop/src/carter_2dnav/params/global_costmap_params.yaml" command="load" />

        <rosparam file="/home/mavric-wonse/catkin_urop/src/carter_2dnav/params/base_local_planner_params.yaml" command="load" />

    </node>

    <node type="rviz" name="rviz" pkg="rviz" args="-d /home/mavric-wonse/catkin_urop/src/carter_2dnav/rviz/carter_2dnav.rviz" />

    </group>

</launch>

Running the Launch Code with Simulation:

In one terminal run the launch file with:
roslaunch demo_isaac_carter_navigation.launch

In another terminal, run the command below to control the robot with the keyboard:

rosrun teleop_twist_keyboard teleop_twist_keyboard.py

Save Point Cloud Data on Rtabmap:

Make sure mapping mode is turned on in rtabmap.

Drive around to create a full map of the environment.

On the rtabmap application, press the pause button on the left sidebar.

Under File, click on export to .pcd or .ply

Save in a location on the computer.