fixing odom drift

edit

Hey, I want to write a python node that publishes tf map->odom, and by that fixes the odometry drift, as the amcl does. I have the base_link desired position in the map, and from that I need to calculate the corract map->odom. I have the code part in amcl that does that. can someone explain what is happening in the following code section?

// subtracting base to odom from map to base and send map to odom instead
  tf::Stamped<tf::Pose> odom_to_map;
  try
  {
    tf::Transform tmp_tf(tf::createQuaternionFromYaw(hyps[max_weight_hyp].pf_pose_mean.v[2]),
                         tf::Vector3(hyps[max_weight_hyp].pf_pose_mean.v[0],
                                     hyps[max_weight_hyp].pf_pose_mean.v[1],
                                     0.0));
    tf::Stamped<tf::Pose> tmp_tf_stamped (tmp_tf.inverse(),
                                          laser_scan->header.stamp,
                                          base_frame_id_);
    this->tf_->transformPose(odom_frame_id_,
                             tmp_tf_stamped,
                             odom_to_map);
  }
  catch(tf::TransformException)
  {
    ROS_DEBUG("Failed to subtract base to odom transform");
    return;
  }

  latest_tf_ = tf::Transform(tf::Quaternion(odom_to_map.getRotation()),
                             tf::Point(odom_to_map.getOrigin()));
  latest_tf_valid_ = true;

  if (tf_broadcast_ == true)
  {
    // We want to send a transform that is good up until a
    // tolerance time so that odom can be used
    ros::Time transform_expiration = (laser_scan->header.stamp +
                                      transform_tolerance_);
    tf::StampedTransform tmp_tf_stamped(latest_tf_.inverse(),
                                        transform_expiration,
                                        global_frame_id_, odom_frame_id_);
    this->tfb_->sendTransform(tmp_tf_stamped);
    sent_first_transform_ = true;
  }