It would have been better if they looked for the densest circle with an area of 1 square km. Although a square shaped area has its tangible benefits - you "feel" population density more when it’s on your own street obviously, and since square areas provide more information along a few axes (the ones containing the corners), you can get an idea of the population density in an area by placing a square’s corners on the street. A square is probably not the best shape for this, though.
twelvechairs|1 year ago