Hi all,

I'm working on a robot equipped with an RGB-D camera.

The pose of the sensor is specified in an urdf file and I can see it has been properly set by running

~$ rosrun tf tf_echo base_link camera_link
At time 0.000
- Translation: [-0.104, 0.018, 0.980]
- Rotation: in Quaternion [0.000, 0.362, 0.000, 0.932]
            in RPY (radian) [0.000, 0.742, 0.000]
            in RPY (degree) [0.000, 42.500, 0.000]

My goal is to retrieve this transformation inside the node I'm implementing. Being a static tf, I can get it by calling a tf::Transformer::lookupTransform inside the constructor of my node:

bool got_tf = false;
while (!got_tf)
{
  try
  {
    listener_.lookupTransform(base_link_frame_id_, robot_camera_frame_id_,
                              ros::Time(0), camera_pose_);
  }
  catch (tf::TransformException ex)
  {
    ROS_ERROR("%s", ex.what());
    ros::Duration(1.0).sleep();
    continue;
  }
  got_tf = true;
}

However, I have some doubts regarding the efficiency of this method:

1. I need to instantiate a tf::TransformListener
2. It's possible that I have to wait some seconds

Therefore, my question is: is there another way (offered by roscpp) to get this transformation? Perhaps, it gets stored on the params server through the urdf?

Thanks

my_tf:
  translation_x: 0.0
  translation_y: 0.0
  translation_z: 0.0
  rotation_x: 0.0
  rotation_y: 0.0
  rotation_z: 0.0
  rotation_w: 1.0

std::map<std::string, double> map_tf;
nh.getParam("my_tf", map_tf);