Precision was easy. The great pyramid's east and west sides are very well aligned with the meridians they lie on. Impressive? Not really. They surveyed well

Precision was easy. The great pyramid's east and west sides are very well aligned with the meridians they lie on. Impressive? Not really. They surveyed well and they used the two near-polar circumpolar start available to them at the time. The would wait until those two stars were aligned vertically to the horizon and then they laid down ropes/strings/markers along the sides and at the corners, then they built within those constraints and the north side necessarily came out shorter than the south side. They might not even have noticed that the north and south sides came out to be different lengths, who knows. There were simple, primitive, and basic astronomic techniques trivially available to the ancient Egyptians for precise layout of large objects like the pyramids. This may seem surprising to us now, but if you think about it, it becomes obvious.