Reviewing Petries “Pyramids and Temples of Gizeh” as outlined here http://www.ronaldbirdsall.com/gizeh/petrie/c6.html Petrie states:
“On the whole, we probably cannot do better than take 51º 52' ± 2' as the nearest approximation to the mean angle of the Pyramid, allowing some weight to the South side. The mean base being 9068.8 ± .5 inches, this yields a height of 5776.0 ± 7.0 inches.”
This is based on a simple application of the tan function to the angle measured. My question is related to the margin of error that Petrie claims of less than 7 inches. This does seem reasonable on first glance due to the exhaustive set of measurements he documents. However he also states:
“it is not at all certain that the courses of the casing were truly level to 5' or 10', and occasional specimens showed angles up to 54º.”
Is it possible then given the removal of most of the casing stones that the pyramid was higher than Petries measurement could account for?. Here I am suggesting perhaps there could have been more or even an entire level of 54 degree casing stones and therefore he should have factored in a broader margin for error? I note that an increase of 30’ (minutes or 0.5 degree would increase the height by around 2%.)
You left out some important context that answers your question:
In assigning the weights to these different data, the reason that no weight is given to the angles of shifted casing stones is that there is no proof that the courses did not dip inwards somewhat; on the contrary, I continually observed that the courses of the core had dips of as much as ½º to 1º so that it is not at all certain that the courses of the casing were truly level to 5' or 10', and occasional specimens showed angles up to 54º.
Meaning he infers the 54° from the amount of dip, not because casing stones with that angle were found.
Good pickup - I had definitely misinterpreted that statement. On reflection it appears to refer to the core dipping occasionally and he did take a mean or average measurement. What it doesn’t resolve is the size and angle of the casing stones that sit on top of the core. He goes on to discuss this sizing with the evidence he has available to him which is in accordance with his theory. My question revolves more around the large amount of evidence that was no longer available to Petrie ie the bulk of the casing stones and whether that should have influenced the margin of error reported.
D. I. Lightbody, ‘Biography of a Great Pyramid Casing Stone’, JAEA 1, 2016, pp. 39-56. http://www.egyptian-architecture.com/JAEA1/article3/JAEA1_Lightbody.pdf
Quoting :”Although large parts of the stone are broken off and missing, its overall rectilinear dimensions can be reconstructed from the surviving material, with a margin of error of +/- 5 mm, as follows: 65 cm wide52 cm in height93 cm from front to rear at the base 51 cm from front to rear on the top. “
MAX Height: 52.5 cm Min difference between front to rear at base and at top: 92.5 - 51.5 = 41
Based on this would yield an angle of 52 degrees and the Great Pyramid could be up to 1.7 cubits or 89cm taller than the generally accepted 280 Royal Cubits based on Petries study.
The comment previously that Petries commentary about occasional samples being 54 degrees was definitely about the core masonry measures upon a re-read. This got me wondering whether there had been any follow up attempts to survey the Great Pyramid since Petrie. I found papers referenced in the Lightbody study for Cole and Dash surveys. Incredibly, these surveys only looked at the baselength and not the angle of the slope.
We are told that an earthquake hit the area enabling the removal of the casing stones. Is it possible then that the core stones also shifted causing the dips Petrie spoke of? Therefore should we allow for an additional margin of error?