Practical Electron Microscopy and Database

You can imagine a crystal located inside a sphere as shown in Figure 4123. Draw lines normal to corresponding crystal planes from the center of the sphere to intersect the sphere at point N_s (N₁ to N_n) in the northern hemisphere (There are 5 Ns shown in the crystal example). Similarly, there are 5 Ss (S₁ to S₅) shown in the southern hemisphere and there are 6 Ps (P₁ to P₆) shown on the equatorial plane. This projection on the sphere is called spherical projection.

Figure 4123. The spherical projection. The crystal is located at the center of the sphere.