In some of the overhead images from Gripp Patch, one can faintly see a straight line projecting into each of the four grand cardinal disks.  In the overhead imagery, these lines are easy to miss; but not so on the ground.  On the ground, one sees they are extensions of the central cross (X) that links the four cardinal disks; in other words, the four "corners" of the square.  Furthermore, each line terminates or commences at the disk's centre. 

Finally, on the ground, one sees another faint ring that passes through the centre of each of the four grand disks, and the eight smaller disks as well . . . a circle bounding the square defined by the four grand disks . . . "a circle squared."  And these faint lines are marvellously interwoven with the weave of the disks themselves; it's quite marvellous!  How does one do such things with a board and rope?  The answer is obvious, I think.  ;-)