Stonehenge Aubrey is 897.60 imperial feet x 3.5 = 3141.60 based on a circumference of 330 x 2.72.
Also Dune has G2 designed against 3.1416 on one of his many posts , I can't locate it but this is how it can be calculated using the canon of ancient measure not the use of base 100.
The theory is that the imperial design of the GP tops out at 366.666 base side x 360 x 1000 = 132000000 units.
132000000/42000000 is 22/7 as an exploded version.
To get to 3.1416 take 100 x 528 imperial feet off this to give 132000000-52800/42000000 = 3.1416