TF tutorials question

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Hello,

I am new to tf and in ros in general - so some follow up questions may rise. My main questions will be marked with bold. I have built a 3 wheel robot on which I have put a lidar (hokuyo_link) and I am trying to setup the tf for my robot. I have managed to manipulate the lidar data for some simple obstacle avoidance movements, but my aim is to use the navigation stack and a main prerequisite for that is the tf. So what I am trying to implement is a odom -> base_link -> hokuyo_link tf, if I have understood correctly the logic.

For a start, I want to create a tf between my lidar and my base_link. For this purpose, I am following this tutorial and I have some questions.

I have wrote a broadcaster -do I need this broadcaster or it is implemented automatically from gazebo during simulation? - copied from the tutorial but changed with my geometric data, and I am trying to write a listener:

#include <ros/ros.h>
#include <geometry_msgs/PointStamped.h>
#include <tf/transform_listener.h>

void transformPoint(const tf::TransformListener& listener){
  //we'll create a point in the base_laser frame that we'd like to transform to the base_link frame
  geometry_msgs::PointStamped laser_point;
  laser_point.header.frame_id = "hokuyo_link";

  //we'll just use the most recent transform available for our simple example
  laser_point.header.stamp = ros::Time();

  //just an arbitrary point in space
  laser_point.point.x = 1.0;
  laser_point.point.y = 0.2;
  laser_point.point.z = 0.0;

  try{
    geometry_msgs::PointStamped base_point;
    listener.transformPoint("base_link", laser_point, base_point);

    ROS_INFO("base_laser: (%.2f, %.2f. %.2f) -----> base_link: (%.2f, %.2f, %.2f) at time %.2f",
        laser_point.point.x, laser_point.point.y, laser_point.point.z,
        base_point.point.x, base_point.point.y, base_point.point.z, base_point.header.stamp.toSec());
  }
  catch(tf::TransformException& ex){
    ROS_ERROR("Received an exception trying to transform a point from \"hokuyo_link\" to \"base_link\": %s", ex.what());
  }
}

int main(int argc, char** argv){
  ros::init(argc, argv, "robot_tf_listener");
  ros::NodeHandle n;

  tf::TransformListener listener(ros::Duration(10));

  //we'll transform a point once every second
  ros::Timer timer = n.createTimer(ros::Duration(1.0), boost::bind(&transformPoint, boost::ref(listener)));

  ros::spin();

}

The only thing I changed is the name used for the laser link. The arbitrary point used in the tutorial are in my case my lidar data? And also, if my previous question has a positive answer, this means that the node that listens to the tf channel, needs to subscribe to the /laser/scan topic to get the data ?

Thanks for your answers and for your time in advance, Chris

P.S.: I am sorry if my question seems messed up, I am new to ros.