@mitcorb said: Question- what is the function of the U bar suspended down below? The U-bar is used by the tractor driver to gauge the height of the plants he is running over. The IR sensor rack is raised so the bottom of that bar brushes over the tops of the plants. I think that determines the area that the sensors can "see".

http://www.youtube.com/watch?v=wpGpJwlhwck A demo of one way to make a sphere with a hole...