How to rig a rain tarp without trees -- poles, maybe??

firemedic, I am talking about a really big rain tarp -- I've seen them set up at about 20 feet by 40 feet, with the central rope at a diagonal across the tarp. It forms a roof that sheds water and keeps the whole campsite dry. Those small gazebos don't have a big enough "footprint."

Keep those ideas coming! Maybe helium balloons??