Thank you for responding to my post.

In Appendix A of my 2006 monograph on the Grand Gallery of the Great Pyramid (published in 2006 and in the collection of the Sackler Library, Oxford) I noted that:

On the east side, the line of the Corner Sockets is parallel to the Base Square. For the north side, there is a slight deviation between the line of the Base Square and the line of the Corner Sockets, with the following effect:

1) The alignment of the north edge to the East-West parallel is slightly better for the Base Square than for the line of the Corner Sockets.

2) The right angle on the Base Square, at the north-east corner, is not quite as perfect as the right angle on the N.E. Corner Socket.

It is reasonable to conclude that the east side was built first, as concluded by Maragioglio and Rinaldi, and that the north east corner of the Base Square does not have as perfect a right angle as that of the N.E. corner socket because the north side had an east-west solar alignment based on the equinox. Glen Dash carried out practical work to show how this might have been done very precisely.

The north-west corner of the Base Square is close to a perfect right angle so the west side points to true north better than the east side simply because the east-west parallel was determined more precisely than true north, as apparent from the east side.

As such one would expect the south-east corner of the Base Square to be close to a perfect right angle, and for the south side to be close to parallel to the north side which is indeed the case.

It follows that the SE corner of the Base Square should be the least perfect right angle because it arises from the difference between the line of polar pointing on the east side and the north-south line of the west side based on near perfect right angles to the north and south sides.

We now know that the west side is more perfectly aligned to true north that the east side which suggests the solar method was more precise than the stellar method. Perhaps the architect thought this was the case because the Base Square appears to have two east-west determinations and only one north south determination, although with so few determinations it may be just be a chance that the east-west orientation was determined more precisely. Either way, it seems likely that the architect was aware of the difference and chose not to make the west side parallel to the east side.

The solar method promoted by Glen Dash means that true north could have been determined at any time without a stellar alignment, but it seems that the architect chose to determine true north from a stellar alignment, possibly because it was so easy in 2790 BC or because it was regarded as important to do so at some other date.

I put my model to Prof. Ramsey who advised that he was sure my date of 2840 BC for the foundation (and alignment) of Khufu's Pyramid was incorrect from his radiocarbon studies. I accepted that my theory was wrong as confirmed to me by Jaromir Malek, also of Oxford, who advised that the inscription recording the helical rising of Sirius on New Year's Day was not actually in Menkaure's reign, but translated incorrectly as such.

In 1970, Dr I.E.S. Edwards noted that radiocarbon dating had determined the age of rope from Khufu's funerary boat at 2536 BC, plus or minus 105 years, and that this was in good agreement with a historical date of approximately 2570 BC from the chronology of kings. It seems that fifty years later the estimate of 2570 BC is still reasonable.

I now think that Khufu's Pyramid may have been built at a known number of years from the inception of the Egyptian calendar c.2770 BC, possibly in the period 2600 to 2550 BC, but if so the architect chose not to align the east side to the maximum elongation due west of Alpha Draconis. The east side is so close to the pole that it is reasonable to conclude that the objective was to align the pyramid to the pole of the night sky, not the pole star.

It is not surprising that Egypt's most precisely built pyramid turns out to be the most precisely aligned to true north.

It seems very unlikely that Khufu laid the base for Khafre's pyramid because his chosen son finished his boat pit, but chose to build his pyramid elsewhere.

In my opinion the design of Khufu's sarcophagus, aligned north-south along its length, has a bold assertion of the east-west line latent in its design, but I have not yet had time to present the geometric model to this forum.

Mark