There's a ratio involving pi between the base lengths of the pyramid and its height. This is been interpreted by enthusiasts that the Egyptians knew about pi.
But, consider a measuring wheel, where you can mark off distances very accurately by counting revolutions of the wheel, say, 1 cubit in diameter (I know, I know, what's a cubit?). Then, if the height is laid out in cubits, the ratio of pi is there while being completely ignorant of it.
Well if you want to calculate the circumference of earth and know the distance between Alexandria and Syene, where the sun casts no shadow at noon during the summer solstice, you also need to know pi.
If you know the angle and the distance between the two cities, you can just multiply the distance by [full circle divided by the angle], and that's the circumference.
When I was a boy, I asked my mom how the Egyptians made their pyramid foundations straight. Without looking up from her book, she replied "pull a string tight". Then I thought I'd trip her up with how they made the foundation level. Without hesitation she said "dig a trench and fill it with water."
She shoulda been an engineer!
I have responded to a sibling comment with more information or examples. I hate this because I don't care about pyramids or Egypt, but I feel myself compelled to respond, I'm so sorry it's not against you, It's a recent pet peeve.
What's an ark?