Hi Mark,
I’ve been wrestling with the Royal cubit issue for a long time. Most don’t realize Petrie published “Inductive Metrology” 5 or so years before arriving at Giza. Given the voluminous extent of his measurements of all 4th dynasty pyramids, temples and tombs he was able to confidently identify the 4th dynasty royal cubit (weighted mean) equal to 20.62 +/- .01 inches and provided a weighted mean for the Kings Chamber (G1) of 20.62 +/- .005 inches. Since determining these weighted means no other surveys atop the Giza Plateau have collected enough data to challenge his results. Often, even Petrie himself, people round up the royal cubits for Khufu to 440 per side, but all current weighted mean values suggest or indicate 439.82 Royal cubits… dead on for 20.62”, where as 440 requires 20.61”. So, there is another check at Giza using Khafre’s pyramid side length… 411 Royal cubits is dead on using 20.62” and is confirmed by M & R and Petrie surveys. I guess in a general sense folks like whole numbers for analysis, but the archaeological record reveal’s otherwise.

20.62 inches equals .5237 meters

B.A.Hokom