strands_perception_people_msgs/PedestrianTracking meaning

[hawesie]

I'm looking to inspect the tracked pedestrians to see if one is within a given range for a particular length of time. With the pose array I can easily do the distance, but I can't check whether the same track uuid reoccurs. Looking at PedestrianTracking I can see that I can get the uuid but, not being able to run the system right now (at home with laptop), I can't work out what frame the x,y,z of these trajectories are in and whether to look at the start of these lists. Does the header frame_id tell me the tf frame used for traj_x etc.?

[cdondrup]

The traj_*_camera values are in the frame_id coordinate system (head_xtion_depth_optical_frame). The traj_* values are some form of world coordinates calculated based on visual features which we don't really need when it's running on the robot. I just use the traj_*_camera coordinates to create the pose message:

        geometry_msgs::PoseStamped poseInCamCoords;
        poseInCamCoords.header = pta.header;
        poseInCamCoords.pose.position.x = pt.traj_x_camera[0];
        poseInCamCoords.pose.position.y = pt.traj_y_camera[0];
        poseInCamCoords.pose.position.z = pt.traj_z_camera[0];

It is then transformed form head_xtion_depth_optical_frame into the given target frame. Therefore, just looking at those values is as good looking at the pose in camera coordinates.

[cdondrup]

Also these values represent a history over the last detections. The first element is the current detection. I don't know the number of detections that are saved in the history from the top of my head, but just looking at the first one gives you the current position.

[hawesie]

Thanks, I'll try this when I get back to the lab.

[hawesie]

Is the id the way to get the tracked person across readings? uuid appears to change every reading.

[cdondrup]

The uuid should be the unique one. I will have a look why it changes.

[cdondrup]

If you don't restart the tracker you can use id as well. The uuid is just created using the startup time of the tracker plus the id.

[hawesie]

Ok, I will stick with id. I'm seeing same id but changing uuid.

[cdondrup]

Above PR fixes the issue. The uuid is now stable as well. But as I said, if you do not restart the tracker or don't care if the ids are consistent even after restart, you can just use the id.