The need to resurvey Egyptian fields after frequent Nile flooding is often cited as a reason for development of Egyptian mathematics. However, it might be noted that Egyptian math was not highly developed. That happened in other regions such as Greece, Persia, India. The level of knowledge of the planet and geometry in the Great Pyramid is high no doubt, but whether it was Egyptian at all is in doubt unless you ask the current Egyptian curator of antiquities Aiwass.
I would not want to argue the point, but suggest a very readable and interesting book. It belies your thoughts and offers severeal proofs of the exceptional egyptian grasp and practcal use of geometry. Pretty hard to beat for $5.00 used
This thead has forced me to read it again. For me it is a standard reference especially for the section on the Golden Section. I always use those proportions in things I design