[General] characteristic of variance along different directions [GIS] It is because the directional difference that the semivariogram values of two pairs of points which have the same distance are not identical, the directional influence is known as anisotropy. Note: Anisotropy differs from the global trend because the global trend can be described by a physical process(eg. the prevailing winds) and modeled by a mathematical formula. The cause of the anisotropy(directional influence) in the semivariogram is not usually known, so it is modeled as random error.
