The diameter of Castle Rigg and hence the total side lengths of any grid of 14 squares, would be measured to be a whole number. to be 107.1 feet by Alexander Thom. The metrology of Egypt, where a grid of 14 squares is to be found evolved within the Rhind manuscript, made extensive use of the royal cubit, 1.5 times the royal foot of 8/7 feet and so 12/7 feet long. [*]
*This unit of length is explicit within stones C3 and R8 at Gavrinis and its derivation has been found by Robin Heath and myself to emerge directly from the use of megalithic yards to count time using one megalithic yard equal to a lunar month - the eclipse year then being one royal cubit less than the solar year.
If Castle Rigg was 108 feet in diameter, then this length is 63 royal cubits and each grid square would be 9/2 = 4.5 royal cubits long. However, one should at least expect the half royal cubit of 6/7 feet to have been available to the builders of Castle Rigg. This would enable the second pair of key points to be found from the first as each being two cubits (24/7 feet) further from the central axis and then being one and a half cubits (18/7 feet) downwards. If a foot is seen as containing twelve inches, then the royal cubit was quite likely to be seen, in its early usage, as also being made up of twelve units, each of 12/7 inch in length [*] and six such units making up 6/7 feet, the half cubit.
* In fact, within the colinear lines of the Gavrinis rock art one finds units of 12/7 inches between adjacent pecked lines and in the Kercado roof axe, a similar underlying unit of 12/7 inches.
All four key points at which the curvature changes within the Type A can therefore be seen to occur systematically within a grid of 14 by 14 squares. The arguments against Thom's hypothesis need to be reviewed since, within this grid, ropes could easily be used to find where stones should lie upon the regular arcs between these key points. However, arguments that stones were only placed approximately, by eye, also becomes achievable since one can easily imagine a quite accurate arc between two points, within such a grid. Meanwhile, the arguments that all such shapes were the result of inaccuracies when circles were intended, is an argument that seems to ignore the systematic conformity found within flattened circles in being symmetrical and flattened only on one side, usually only by about 85 to 90 percent of the circular diameter.