SITL heading mismatch between ROS and FCU?

1

Hi guys,

I have been using Gazebo for sitl lately and I have found an interesting problem, and it might be my lack of understanding of the SITL so I hope you guys can shed some light here.

When I use px4 SITL with Gazebo with mavros_px4_sitl.launch, after launching it, the drone appears and “/mavros/local_position/pose” starts publishing and I can recover yaw from the received quaternion. To illustrate, the default frame is x forward, y left and z upward, and the yaw of the drone is 0 at the start, which is something like below:

                        +x, yaw = 0
                                 ^
                                 |
                                 |
        yaw = 180, +y <----------0    yaw = 270     
                             
                               yaw = 180

But if I opened Qgroundcontrol at the same, I can find a totally different pattern of rotation which looks like below:

                              yaw = 90
                                 ^
                                 |
                                 |
            yaw = 0   <----------0    yaw = 180     
                             
                               yaw = 270

As we can see, these two frames are quite different and they cannot be converted to one another with a simple yaw offset.

This problem has been found on both px4 1.8.0 and the master branch.

Can anyone help me find out what I am doing wrong here?

Thanks for any help!

Joey

2

ROS is in ENU frame while PX4 is in NED frame. Mavros performs the conversion between the two frames. https://dev.px4.io/v1.9.0/en/ros/external_position_estimation.html#ros_reference_frames

3

thanks for the heads up, I got it.