Current map provided with laser scan

Hi, I am new in ROS and I want to do a SLAM using gmapping package with "laser scan" and "odometry data". In the first step I just want to see the current map provided with laser scan in fixed location (x = 0, y = 0, theta = 0) in rviz. I have laser scan topic but I don't have a odometry data yet, so I want to make a fake odometry data. For this I think I should publish a TF data with all zeros. I think I should do some thing like this [link](http://wiki.ros.org/tf#tf_echo): 1 2 3 Am I in the right path? could you please tell me what should I do in details? or show me some references?