"Invalid <arg> tag: mavlink_sitl_gazebo" when exceuting roslaunch px4 posix_sitl.launch

[Daidalos92]

I encountered the following error when running the roslaunch px4 posix_sitl.launch command from the PX4 SITL tutorial. I am running on ubuntu 16.04 ROS kinetic. anyone encountered similar errors or know any possible causes for it? i have already sourced and exported the paths as per below. I am able to run the no_sim=1 make px4_sitl_default gazebo as per normal.

source Tools/setup_gazebo.bash $(pwd) $(pwd)/build/posix_sitl_default
export ROS_PACKAGE_PATH=$ROS_PACKAGE_PATH:$(pwd)
export ROS_PACKAGE_PATH=$ROS_PACKAGE_PATH:$(pwd)/Tools/simulation/gazebo/sitl_gazebo

offboard@user:~/src/Firmware$ **roslaunch px4 posix_sitl.launch**
... logging to /home/offboard/.ros/log/2bc60f36-954e-11ed-830e-f45c89c15fb5/roslaunch-user.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

**Invalid <arg> tag: mavlink_sitl_gazebo**
ROS path [0]=/opt/ros/kinetic/share/ros
ROS path [1]=/home/offboard/catkin_ws/src/mavlink
ROS path [2]=/home/offboard/catkin_ws/src/mavros/libmavconn
ROS path [3]=/home/offboard/catkin_ws/src/mavros/mavros_msgs
ROS path [4]=/home/offboard/catkin_ws/src/mavros/mavros
ROS path [5]=/home/offboard/catkin_ws/src/mavros/mavros_extras
ROS path [6]=/home/offboard/catkin_ws/src/mavros/test_mavros
ROS path [7]=/opt/ros/kinetic/share
ROS path [8]=/home/offboard/src/Firmware
ROS path [9]=/home/offboard/src/Firmware/Tools/simulation/gazebo/sitl_gazebo. 

Arg xml is <arg default="$(find mavlink_sitl_gazebo)/worlds/empty.world" name="world"/>
The traceback for the exception was written to the log file

[Jaeyoung-Lim]

Which version of px4 are you running?

[Daidalos92]

I git cloned the v1.9.2 tag from the main PX4 repository.

[Jaeyoung-Lim]

@Daidalos92 I no longer remember how it was done in v1.9.2

You can check whether px4 is on the ROS_PACKAGE_PATH

Otherwise, Ubuntu 16.04 is is EOL and I recommend you to update your setup

[Daidalos92]

@Jaeyoung-Lim Hi thanks for your help, I realised the architecture is a bit different in the version im using in that instead of Firmware/Tools/simulation/gazebo/sitl_gazebo, my sitl_gazebo is in the directory Firmware/Tools/sitl_gazebo. rospack find mavros_sitl_gazebo shows

rospack find mavlink_sitl_gazebo
/home/offboard/src/Firmware/Tools/sitl_gazebo

I no longer get that error when trying to launch the sitl but i now faced another error ResourceNotFound: gazebo_ros. Do i need to install the gazebo_ros package from source?

[Jaeyoung-Lim]

No you should have access to gazebo_ros through your package manager.

However, since Ubuntu 16.04 is end of life, I am not sure whether this is still available