rosrun tf tf_echo /map /base_link VS. Coding implementation. [closed]

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Hi,

I want to calculate robot's current position with respect to the map. Following is my "rosrun tf view_frames"

tf tree

I have tried following commands which gives robot position with respect to /map frame.

rosrun tf tf_echo /map /base_link

Output is here:map to base_link.jpg

Now same thing, I tried to perform using the code here

But the output of rxconsole is shown below:: transform.jpg.

I am just wondering why the results of the code and that of "rosrun tf tf_echo /map /base_link" is not matching?

I am getting "Got a transform! x = 0.000000, y =0.000000", even after 1sec when I use the code. But "rosrun tf tf_echo /map /base_link", gives actual robot position with respect to the map as you can see the screen shot.

Question1: Is there any way to get the exact position of the robot while moving in the environment?

Question 2: I don’t know how the above command gives position of the robot with respect to the map, but the implementation of the SAME COMMAND gives some INVALID result?

Question 3: Is there any way to emulate the command "rosrun tf tf_echo /map /base_link" in coding?

Please help..........

Many Thanks.