A recent post on Edible Geography reminded me of these strange pivot circles I had found in Google Earth. Some of these circles were just too big and they seemed squeezed from the sides:
According to the article on Edible Geography: “These overlooked corners (in the square grid, red) make up a not insubstantial percentage of a farmer’s available land. On a typical 160 acre “quarter section” in the American mid- and southwest, tessellating pivot circles will leave up to 24 acres, or 15 percent of each field, thirsty.
For me, living in the Netherlands, this is hard to understand. A Dutch farmer will do anything to use every percentage of the land he owns.
If you take a closer look you can see why the oversized circles are shaped this way: at the end of the pivot is a hinge. This hinge is extending the pivot in the corners of the square and irrigating a substantial part of these corners.
Sometimes you can find small pivots turning in the empty corners between the big circles, although very rare..
If you want to dig deeper into the American grid and into pivot irrigation: here is a nice online article on The Great American Grid website: The Art of the Circle Field