Thank you Leon and Waggy. It would seem the problem is poor survey data and the 'elasticity' of the cubit. Nobody knows how it was originally defined but most authorites give average values around 0.523 to 0.525 m. But at different sites it could vary more widely - Waggy shows that the Red pyramid chamber complex was laid out using 0.522, while Khufu chamber and passage system requires a longer cubit, derived from key dimensions obviously intended as whole numbers. Undoubtedly master standards existed, and perhaps during the transmission of copies to overseers of building projects, and copies to building crews tasked with a particular project (say the layout of the Red chambers) standards dropped. I would anyway think the proportions of any particular layout was rather more important to them than precise measurement (unless of course the dimensions had to correspond, say, to some geodetic scheme).

But whatever the cause, these variations become important over large distances. Petrie needed a cubit of 0.5263 to derive his 360 base; but 362 requires 0.5234 which is rather nearer to the Old Kingdom average we might expect. It also makes sense (as I proposed below in the thread on 'Pyramid design before Khufu'). Legon explains the 362 base of the Bent using a root two construction within the enclosure of 560 cubits side to produce the proportion 99 : 181. However the proposed root three construction links the Bent and Red together. So were they designed at the same time? Was the Bent form intentional or was it a fudge job as Monnier proposes? And perhaps most interesting, what is the theoretical slope of the Red?