Cardinal Alignment Precision

The Great Pyramid's base sides are aligned to true north, south, east, and west with an accuracy of 3 arc-minutes (3/60th of a degree), or about 0.05°. This surpasses the alignment accuracy of the Greenwich Observatory, built in 1675. To achieve this, the builders needed either sophisticated astronomical observation techniques (tracking circumpolar stars) or instruments of extraordinary precision. The alignment was likely performed using the transit of stars across the meridian, possibly Alpha Draconis (Thuban), which was the pole star circa 2500 BCE. This level of precision also means they had to account for the curvature of the Earth across the 230-meter base.