RE “pyramid of Giza … at the intersection of the longest line of latitude and the longest line of longitude” The longest line of latitude is the equator, or slightly north or south of that because of irregularies in the Earth’s surface. But certainly not 29.9 degrees north, where Giza is.
The claim that the pyramids were NOT build by slaves is based on very shaky evidence. It was based on excavations of the graves of the workers. But evidence was things like, “dead workers were buried near the work site, and no way would slaves have been buried in such an honored place”. Well, maybe. Or maybe they dumped the bodies in the nearest convenient place. They made much of the fact that many of the bodies were wound with the remains of a jar of food, a common Egyptian burial custom of the day, comparable to modern Americans putting flowers on a grave. So they gave the dead some modicum of respect. That’s nice, but if some future archaeologist discovered that black plantation workers in the 1850s were buried with a cross and some flowers on the grave, that would hardly prove that they weren’t slaves. And … that’s about it. That’s the evidence that they weren’t slaves.
The archaeologist who made this claim, Zahi Hawass, admitted that the bodies showed signs of a very hard life, including bone disease and damaged vertebrae, and that most died very young. This is totally consistent with the idea that they were slaves and not at all consistent with them being “highly paid professionals”.