Running usb_cam node

I have created a launch file with the help from this guide: http://www.princeton.edu/~ctralie/Projects/DukeDusty2/Tutorial/

Note: /dev/video0 is the device of the integrated webcam of my laptop and /dev/video1 is the device of the Logitech Quickcam I am currently using.

When running this launch file with the /dev/video0 device I can successfully visualize video on rviz. However, a status error is displayed:

CameraInfo/P resuted in an invalid  position calculation (nans or infs)

According to ROS users, I should calibrate my camera in order to avoid this error. I had no idea on how to do so until I found this tutorial:

http://www.ros.org/wiki/camera_calibration/Tutorials/MonocularCalibration. I hope this does the trick.