Hello and first thanks for reading,
as I'm quite new in ros, and quite completely new in tf package, my problem was the next, I wanted to use tf package to transform a point cloud(with position changing in time) with reference to world(0,0,0). I have seen the tf tutorials, that helps to create frames starting by frames added by turtlesim, and that package creates the firsts frames, so I couldn't be able to understand how it have been done.
So I wanted to create or run the world frame, with NO_PARENT, but I didn't want turtlesim package to do this because it runs 2 nodes more(at least keeping the tutorials of tf: http://www.ros.org/wiki/tf/Tutorials) and I didn't wanted to add rubbish that I would have not used,
would it be possible to just run or add a world frame with no others frames, so I could then add a just the frames I interest??
For putting you in scene I have used a moving "robot" with a gps(using gpsd_client package) and a laser(using hokuyo_node package) fixed on the robot, and I would like to transform the scan point cloud to have every scan done (by laser) with the position(given by gps) where it has been scanned, so I need just 2 frames, the world frame (reference frame, I think it should be the (0,0,0)) and a frame with defines the scan position (with the same position as provided by gps), that would be changing in time according to the robot moves.
As I asked and according to Lorenz recommendations(sorry for before and hope it would be better now), I keep the question edited with question and you will see the answer by Lorenz down this question, that was if someone could help me at least to run or add a simple fixed frame world and I could continue with adding the target moving frame. Althought adding the moving frame should be the difficult and not the world frame, I had found some tutorials to do this that I could try to check, but according to easy question add a fixed world frame, I have not found the solution althought finding a lot.
So if you had the same problem just read now Lorenz answer, if I understood well (still couldn't try it) it's been done automatically when you send any transform, if the parent frame doesn't exist it's been create automatically as a NO_PARENT frame (0,0,0). In any case read his post to better understand.
Excuse my english and again thank you very much for your patience,
special thanks for you Lorenz!
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