I'm following this tutorials: [http://learn.turtlebot.com/2015/02/03/11/] ,and I can get the position and ERY of my turtlebot based on the map frame, but I want to get those number from one moment t=t0 (position[xo,y0,z0],ERY[a0,b0,c0]) in my node written by C++. I know what I should do is subscribe tf. And according to wiki tutorials, tranformListener can automatically subscribe all the information from tf, like this tf::TransformListener listener; but aftrer that I just don't know what to do. All I need is the position and ERY of the current location of my turtlebot. Thank you guys!