The angles obtained in building were certainly accurate to within less than a few millimetres. I forget how much, but certainly a system of measurement that was not equalled until laser measurement was established. Not only that but they were built on a linear system that stretched between continents. Given that, the measurements had to have been triangulated from the stars and with a similar purpose in mind. As people as late the 1500s were still being executed for stating that the sun orbited the earth, geometry had regressed since the building of the pyramids to junior school level.I have wondered if the angles had anything to do with the building.