Dear ros-users:

      I am learning *Building a Map in Simulation* in the website of *
http://www.ros.org/wiki/pr2_simulator/Tutorials/BuildingAMapInSimulation*.
When I begin to run the second step "roslaunch pr2_gazebo_wg
map_building_demo.launch", it gets errors showing in the accessory. And the
error happened in the last three lines in the error.txt.  What happened?
Thanks in advanced!

Eileen
TJ University of Shang Hai