I have to tell you that I wondered why Petrie had opted for a length of 20.632 inches when so many measurements pointed to 20.61 inches, including his assessment of the perimeter of the base square (20.611 inches from memory).

I then found that in 1877 he published that the royal cubit was certainly another length, plus or minus a small amount, and this just allowed for 20.632 inches but not 20.61 inches.

All the statistics in his book on inductive metrology would become worthless if he had accepted a value of 20.61 inches.

I was rather pleased to discover that all sides of the Great Pyramid correspond to a royal cubit with a length of 20.61 plus or minus 0.01 inches, as determined by Cole.

If you divide all Petrie's measurements in inches by 20.632, and then draw out the cross-section, it is rather less elegant than for 20.61 inches. I thought this would be the case before I started from Petrie's survey of the Base Square. For example, the peak of the Queen's Chamber is not as close to the east-west axis.

Just accept the fact - Petrie was very good but not perfect - as proved by Cole

Mark