Okay, this is probably not what you were expecting. Reasonable people have recommended reasonable solutions for marking ground control points in aerial photos. So I was looking for something quick and easy to mark the plot corners at an alpine tundra study site south of the Alaska Range.
I decided that party balloons would work great for marking the corner stakes while a kite lofted the cameras over the tundra. I was wrong. There was no wind all day long, and most of the balloons popped or deflated overnight. I replaced them the next morning, but no wind again all day long, just sun and scenery. The next morning there was wind! But the balloons were all gone, and rain was looming, so I flew without party corners.
I did learn that the balloons last longer if they are only half inflated. So the long hotdog shaped ones inflated halfway lasted a whole day.