They use the projection of the sun on the pyramid at noon to calculate the height of the pyramid. Because the height of the sun is the highest at noon, which is about 90 degrees from the ground. At the same time, erect a branch on the ground and measure its shadow length. Now we can calculate how high the proportion of the pyramids is. But we still look silly today. After all, the level of mathematics at that time was not that high. Now we can use the shadow length and width of the pyramid and directly use trigonometric function to calculate the height of the pyramid at any moment.

They are all manual, and I hope to adopt them in time! If you have any questions, just ask!