Directional data in three dimensions. The direction can be specified by the location of a point on a sphere of unit radius. Relative to axes at the centre of the sphere, the location can be expressed in either Cartesian coordinates, (x, y, z) or spherical polar coordinates (1, θ, ϕ). These are related as follows: Spherical data are often represented in two dimensions using a Schmidt net. A distribution commonly used to model spherical data is the Langevin distribution.
Subjects: Probability and Statistics.