They chose the Andes because they needed to measure near the equator, to determine if there really was a difference in sphericity there, and because they reasoned that mountains would give them good sightlines.
他们选择了安第斯山脉，因为他们需要测量靠近赤道的地方，以确定那里的圆度是否真有差异，还因为他们认为山区的视野比较开阔。
![Schematic representation of difference in grain shape. Two parameters are shown: sphericity (vertical) and rounding (horizontal).](/Images/godic/202502/12/Rounding_&_sphericity_EN.svg4205.png")
![\Psi](/Images/godic/202502/12/398b8c3e58e961cdea0fe626771f32434205.png")
, of a particle is: the ratio of the surface area of a sphere (with the same volume as the given particle) to the surface area of the particle: