Measures of geometrically necessary dislocations accessible to experimental determination

Geometrically necessary dislocations (GND) account for the incompatibility of the plastic deformation of single crystals, both in bulk and at the interface. A plethora of measures of GND has been proposed in the literature since 1952: we propose a rationale to choose among these measures, also in relation with recent experimental techiques based on electron backscattering to determine lattice orientation in single crystals.